Previously, GetOrCreateMultiVersionResolver() required the caller to provide
a GlobalDecl along with an llvm::type and FunctionDecl. The latter two can be
cheaply obtained from the first, and the llvm::type parameter is not always
used, so requiring the caller to provide them was unnecessary and created the
possibility that callers would pass an inconsistent set. This change simplifies
the interface to only require the GlobalDecl value.
Reviewed By: erichkeane
Differential Revision: https://reviews.llvm.org/D122956
We expect that `extern "C"` static functions to be usable in things like
inline assembly, as well as ifuncs:
See the bug report here: https://github.com/llvm/llvm-project/issues/54549
However, we were diagnosing this as 'not defined', because the
ifunc's attempt to look up its resolver would generate a declared IR
function.
Additionally, as background, the way we allow these static extern "C"
functions to work in inline assembly is by making an alias with the C
mangling in MOST situations to the version we emit with
internal-linkage/mangling.
The problem here was multi-fold: First- We generated the alias after the
ifunc was checked, so the function by that name didn't exist yet.
Second, the ifunc's generation caused a symbol to exist under the name
of the alias already (the declared function above), which suppressed the
alias generation.
This patch fixes all of this by moving the checking of ifuncs/CFE aliases
until AFTER we have generated the extern-C alias. Then, it does a
'fixup' around the GlobalIFunc to make sure we correct the reference.
Differential Revision: https://reviews.llvm.org/D122608
This builtin returns the address of a global instance of the
`std::source_location::__impl` type, which must be defined (with an
appropriate shape) before calling the builtin.
It will be used to implement std::source_location in libc++ in a
future change. The builtin is compatible with GCC's implementation,
and libstdc++'s usage. An intentional divergence is that GCC declares
the builtin's return type to be `const void*` (for
ease-of-implementation reasons), while Clang uses the actual type,
`const std::source_location::__impl*`.
In order to support this new functionality, I've also added a new
'UnnamedGlobalConstantDecl'. This artificial Decl is modeled after
MSGuidDecl, and is used to represent a generic concept of an lvalue
constant with global scope, deduplicated by its value. It's possible
that MSGuidDecl itself, or some of the other similar sorts of things
in Clang might be able to be refactored onto this more-generic
concept, but there's enough special-case weirdness in MSGuidDecl that
I gave up attempting to share code there, at least for now.
Finally, for compatibility with libstdc++'s <source_location> header,
I've added a second exception to the "cannot cast from void* to T* in
constant evaluation" rule. This seems a bit distasteful, but feels
like the best available option.
Reviewers: aaron.ballman, erichkeane
Differential Revision: https://reviews.llvm.org/D120159
Currently we use the `-fembed-offload-object` option to embed a binary
file into the host as a named section. This is currently only used as a
codegen action, meaning we only handle this option correctly when the
input is a bitcode file. This patch adds the same handling to embed an
offloading object after we complete code generation. This allows us to
embed the object correctly if the input file is source or bitcode.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D120270
Due to various implementation constraints, despite the programmer
choosing a 'processor' cpu_dispatch/cpu_specific needs to use the
'feature' list of a processor to identify it. This results in the
identified processor in source-code not being propogated to the
optimizer, and thus, not able to be tuned for.
This patch changes to use the actual cpu as written for tune-cpu so that
opt can make decisions based on the cpu-as-spelled, which should better
match the behavior expected by the programmer.
Note that the 'valid' list of processors for x86 is in
llvm/include/llvm/Support/X86TargetParser.def. At the moment, this list
contains only Intel processors, but other vendors may wish to add their
own entries as 'alias'es (or with different feature lists!).
If this is not done, there is two potential performance issues with the
patch, but I believe them to be worth it in light of the improvements to
behavior and performance.
1- In the event that the user spelled "ProcessorB", but we only have the
features available to test for "ProcessorA" (where A is B minus
features),
AND there is an optimization opportunity for "B" that negatively affects
"A", the optimizer will likely choose to do so.
2- In the event that the user spelled VendorI's processor, and the
feature
list allows it to run on VendorA's processor of similar features, AND
there
is an optimization opportunity for VendorIs that negatively affects
"A"s,
the optimizer will likely choose to do so. This can be fixed by adding
an
alias to X86TargetParser.def.
Differential Revision: https://reviews.llvm.org/D121410
The purpose of this change is to fix the following codegen bug:
```
// main.c
__attribute__((cpu_specific(generic)))
int *foo(void) { static int z; return &z;}
int main() { return *foo() = 5; }
// other.c
__attribute__((cpu_dispatch(generic))) int *foo(void);
// run:
clang main.c other.c -o main; ./main
```
This will segfault prior to the change, and return the correct
exit code 5 after the change.
The underlying cause is that when a translation unit contains
a cpu_specific function without the corresponding cpu_dispatch
the generated code binds the reference to foo() against a
GlobalIFunc whose resolver is undefined. This is invalid: the
resolver must be defined in the same translation unit as the
ifunc, but historically the LLVM bitcode verifier did not check
that. The generated code then binds against the resolver rather
than the ifunc, so it ends up calling the resolver rather than
the resolvee. In the example above it treats its return value as
an int *, therefore trying to write to program text.
The root issue at the representation level is that GlobalIFunc,
like GlobalAlias, does not support a "declaration" state. The
object which provides the correct semantics in these cases
is a Function declaration, but unlike Functions, changing a
declaration to a definition in the GlobalIFunc case constitutes
a change of the object type, as opposed to simply emitting code
into a Function.
I think this limitation is unlikely to change, so I implemented
the fix by returning a function declaration rather than an ifunc
when encountering cpu_specific, and upgrading it to an ifunc
when emitting cpu_dispatch.
This uses `takeName` + `replaceAllUsesWith` in similar vein to
other places where the correct IR object type cannot be known
locally/up-front, like in `CodeGenModule::EmitAliasDefinition`.
Previous discussion in: https://reviews.llvm.org/D112349
Signed-off-by: Itay Bookstein <ibookstein@gmail.com>
Reviewed By: erichkeane
Differential Revision: https://reviews.llvm.org/D120266
To make uses of the deprecated constructor easier to spot, and to
ensure that no new uses are introduced, rename it to
Address::deprecated().
While doing the rename, I've filled in element types in cases
where it was relatively obvious, but we're still left with 135
calls to the deprecated constructor.
We have the `clang -cc1` command-line option `-funwind-tables=1|2` and
the codegen option `VALUE_CODEGENOPT(UnwindTables, 2, 0) ///< Unwind
tables (1) or asynchronous unwind tables (2)`. However, this is
encoded in LLVM IR by the presence or the absence of the `uwtable`
attribute, i.e. we lose the information whether to generate want just
some unwind tables or asynchronous unwind tables.
Asynchronous unwind tables take more space in the runtime image, I'd
estimate something like 80-90% more, as the difference is adding
roughly the same number of CFI directives as for prologues, only a bit
simpler (e.g. `.cfi_offset reg, off` vs. `.cfi_restore reg`). Or even
more, if you consider tail duplication of epilogue blocks.
Asynchronous unwind tables could also restrict code generation to
having only a finite number of frame pointer adjustments (an example
of *not* having a finite number of `SP` adjustments is on AArch64 when
untagging the stack (MTE) in some cases the compiler can modify `SP`
in a loop).
Having the CFI precise up to an instruction generally also means one
cannot bundle together CFI instructions once the prologue is done,
they need to be interspersed with ordinary instructions, which means
extra `DW_CFA_advance_loc` commands, further increasing the unwind
tables size.
That is to say, async unwind tables impose a non-negligible overhead,
yet for the most common use cases (like C++ exceptions), they are not
even needed.
This patch extends the `uwtable` attribute with an optional
value:
- `uwtable` (default to `async`)
- `uwtable(sync)`, synchronous unwind tables
- `uwtable(async)`, asynchronous (instruction precise) unwind tables
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D114543
The module flag to indicate use of hostcall is insufficient to catch
all cases where hostcall might be in use by a kernel. This is now
replaced by a function attribute that gets propagated to top-level
kernel functions via their respective call-graph.
If the attribute "amdgpu-no-hostcall-ptr" is absent on a kernel, the
default behaviour is to emit kernel metadata indicating that the
kernel uses the hostcall buffer pointer passed as an implicit
argument.
The attribute may be placed explicitly by the user, or inferred by the
AMDGPU attributor by examining the call-graph. The attribute is
inferred only if the function is not being sanitized, and the
implictarg_ptr does not result in a load of any byte in the hostcall
pointer argument.
Reviewed By: jdoerfert, arsenm, kpyzhov
Differential Revision: https://reviews.llvm.org/D119216
code object version determines ABI, therefore should not be mixed.
This patch emits amdgpu_code_object_version module flag in LLVM IR
based on code object version (default 4).
The amdgpu_code_object_version value is code object version times 100.
LLVM IR with different amdgpu_code_object_version module flag cannot
be linked.
The -cc1 option -mcode-object-version=none is for ROCm device library use
only, which supports multiple ABI.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D119026
This issue is an oversight in D108621.
Literals in HIP are emitted as global constant variables with default
address space which maps to Generic address space for HIPSPV. In
SPIR-V such variables translate to OpVariable instructions with
Generic storage class which are not legal. Fix by mapping literals
to CrossWorkGroup address space.
The literals are not mapped to UniformConstant because the “flat”
pointers in HIP may reference them and “flat” pointers are modeled
as Generic pointers in SPIR-V. In SPIR-V/OpenCL UniformConstant
pointers may not be casted to Generic.
Patch by: Henry Linjamäki
Reviewed by: Yaxun Liu
Differential Revision: https://reviews.llvm.org/D118876
Even if the reference itself is dllexport, the temporary should not be.
In fact, we're already giving it internal linkage, so dllexporting it
is not just wasteful, but will fail to link, as in the example below:
$ cat /tmp/a.cc
void _DllMainCRTStartup() {}
const int __declspec(dllexport) &foo = 42;
$ clang-cl -fuse-ld=lld /tmp/a.cc /Zl /link /dll /out:a.dll
lld-link: error: <root>: undefined symbol: int const &foo::$RT1
Differential revision: https://reviews.llvm.org/D118980
Branch protection in M-class is supported by
- Armv8.1-M.Main
- Armv8-M.Main
- Armv7-M
Attempting to enable this for other architectures, either by
command-line (e.g -mbranch-protection=bti) or by target attribute
in source code (e.g. __attribute__((target("branch-protection=..."))) )
will generate a warning.
In both cases function attributes related to branch protection will not
be emitted. Regardless of the warning, module level attributes related to
branch protection will be emitted when it is enabled via the command-line.
The following people also contributed to this patch:
- Victor Campos
Reviewed By: chill
Differential Revision: https://reviews.llvm.org/D115501
Intel's CET/IBT requires every indirect branch target to be an ENDBR instruction. Because of that, the compiler needs to correctly emit these instruction on function's prologues. Because this is a security feature, it is desirable that only actual indirect-branch-targeted functions are emitted with ENDBRs. While it is possible to identify address-taken functions through LTO, minimizing these ENDBR instructions remains a hard task for user-space binaries because exported functions may end being reachable through PLT entries, that will use an indirect branch for such. Because this cannot be determined during compilation-time, the compiler currently emits ENDBRs to every non-local-linkage function.
Despite the challenge presented for user-space, the kernel landscape is different as no PLTs are used. With the intent of providing the most fit ENDBR emission for the kernel, kernel developers proposed an optimization named "ibt-seal" which replaces the ENDBRs for NOPs directly in the binary. The discussion of this feature can be seen in [1].
This diff brings the enablement of the flag -mibt-seal, which in combination with LTO enforces a different policy for ENDBR placement in when the code-model is set to "kernel". In this scenario, the compiler will only emit ENDBRs to address taken functions, ignoring non-address taken functions that are don't have local linkage.
A comparison between an LTO-compiled kernel binaries without and with the -mibt-seal feature enabled shows that when -mibt-seal was used, the number of ENDBRs in the vmlinux.o binary patched by objtool decreased from 44383 to 33192, and that the number of superfluous ENDBR instructions nopped-out decreased from 11730 to 540.
The 540 missed superfluous ENDBRs need to be investigated further, but hypotheses are: assembly code not being taken care of by the compiler, kernel exported symbols mechanisms creating bogus address taken situations or even these being removed due to other binary optimizations like kernel's static_calls. For now, I assume that the large drop in the number of ENDBR instructions already justifies the feature being merged.
[1] - https://lkml.org/lkml/2021/11/22/591
Reviewed By: xiangzhangllvm
Differential Revision: https://reviews.llvm.org/D116070
HIP program with printf call fails to compile with -fsanitize=address
option, because of appending module flag - amdgpu_hostcall twice, one
for printf and one for sanitize option. This patch fixes that issue.
Patch by: Praveen Velliengiri
Reviewed by: Yaxun Liu, Roman Lebedev
Differential Revision: https://reviews.llvm.org/D116216
Use the AttributeSet constructor instead. There's no good reason
why AttrBuilder itself should exact the AttributeSet from the
AttributeList. Moving this out of the AttrBuilder generally results
in cleaner code.
Cases where there is a mangling of a cpu-dispatch/cpu-specific function
before the function becomes 'multiversion' (such as a member function)
causes the wrong name to be emitted for one of the variants/resolver,
since the name is cached. Make sure we invalidate the cache in
cpu-dispatch/cpu-specific modes, like we previously did for just target
multiversioning.
to repro error.
As mentioned yesterday, I've got a problem that I can only reproduce on
Godbolt (none of the build configs on my local machine!), so this is at
least somewhat usable until I figure out a cause.
I'm attempting to debug an issue that I can only get to happen on
godbolt, where the cpu-dispatch resolver for an out of line member
function is generated with the wrong name, causing a link failure.
This class is solely used as a lightweight and clean way to build a set of
attributes to be removed from an AttrBuilder. Previously AttrBuilder was used
both for building and removing, which introduced odd situation like creation of
Attribute with dummy value because the only relevant part was the attribute
kind.
Differential Revision: https://reviews.llvm.org/D116110
Control-Flow Integrity (CFI) replaces references to address-taken
functions with pointers to the CFI jump table. This is a problem
for low-level code, such as operating system kernels, which may
need the address of an actual function body without the jump table
indirection.
This change adds the __builtin_function_start() builtin, which
accepts an argument that can be constant-evaluated to a function,
and returns the address of the function body.
Link: https://github.com/ClangBuiltLinux/linux/issues/1353
Depends on D108478
Reviewed By: pcc, rjmccall
Differential Revision: https://reviews.llvm.org/D108479
Change all uses of the deprecated constructor to pass the
element type explicitly and drop it.
For cases where the correct element type was not immediately
obvious to me or would require a slightly larger change I'm
falling back to explicitly calling getPointerElementType() for now.
With C++17 the exception specification has been made part of the
function type, and therefore part of mangled type names.
However, it's valid to convert function pointers with an exception
specification to function pointers with the same argument and return
types but without an exception specification, which means that e.g. a
function of type "void () noexcept" can be called through a pointer
of type "void ()". We must therefore consider the two types to be
compatible for CFI purposes.
We can do this by stripping the exception specification before mangling
the type name, which is what this patch does.
Differential Revision: https://reviews.llvm.org/D115015
Handle branch protection option on the commandline as well as a function
attribute. One patch for both mechanisms, as they use the same underlying
parsing mechanism.
These are recorded in a set of LLVM IR module-level attributes like we do for
AArch64 PAC/BTI (see https://reviews.llvm.org/D85649):
- command-line options are "translated" to module-level LLVM IR
attributes (metadata).
- functions have PAC/BTI specific attributes iff the
__attribute__((target("branch-protection=...))) was used in the function
declaration.
- command-line option -mbranch-protection to armclang targeting Arm,
following this grammar:
branch-protection ::= "-mbranch-protection=" <protection>
protection ::= "none" | "standard" | "bti" [ "+" <pac-ret-clause> ]
| <pac-ret-clause> [ "+" "bti"]
pac-ret-clause ::= "pac-ret" [ "+" <pac-ret-option> ]
pac-ret-option ::= "leaf" ["+" "b-key"] | "b-key" ["+" "leaf"]
b-key is simply a placeholder to make it consistent with AArch64's
version. In Arm, however, it triggers a warning informing that b-key is
unsupported and a-key will be selected instead.
- Handle _attribute_((target(("branch-protection=..."))) for AArch32 with the
same grammer as the commandline options.
This patch is part of a series that adds support for the PACBTI-M extension of
the Armv8.1-M architecture, as detailed here:
https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/armv8-1-m-pointer-authentication-and-branch-target-identification-extension
The PACBTI-M specification can be found in the Armv8-M Architecture Reference
Manual:
https://developer.arm.com/documentation/ddi0553/latest
The following people contributed to this patch:
- Momchil Velikov
- Victor Campos
- Ties Stuij
Reviewed By: vhscampos
Differential Revision: https://reviews.llvm.org/D112421
See discussion in D51650, this change was a little aggressive in an
error while doing a 'while we were here', so this removes that error
condition, as it is apparently useful.
This reverts commit bb4934601d.
AMD64 ABI mandates caller to specify the number of used SSE registers
when passing variable arguments.
GCC also provides option -mskip-rax-setup to skip the setup of rax when
SSE is disabled. This helps to reduce the code size, see pr23258.
Reviewed By: nickdesaulniers
Differential Revision: https://reviews.llvm.org/D112413
As discussed here: https://lwn.net/Articles/691932/
GCC6.0 adds target_clones multiversioning. This functionality is
an odd cross between the cpu_dispatch and 'target' MV, but is compatible
with neither.
This attribute allows you to list all options, then emits a separately
optimized version of each function per-option (similar to the
cpu_specific attribute). It automatically generates a resolver, just
like the other two.
The mangling however, is... ODD to say the least. The mangling format
is:
<normal_mangling>.<option string>.<option ordinal>.
Differential Revision:https://reviews.llvm.org/D51650
this patch - https://reviews.llvm.org/D110337 changes the way how hostcall
hidden argument is emitted for printf, but the sanitized kernels also use
hostcall buffer to report a error for invalid memory access, which is not
handled by the above patch and it leads to vdi runtime error:
Device::callbackQueue aborting with error : HSA_STATUS_ERROR_MEMORY_FAULT:
Agent attempted to access an inaccessible address. code: 0x2b
Patch by: Praveen Velliengiri
Reviewed by: Yaxun Liu, Matt Arsenault
Differential Revision: https://reviews.llvm.org/D112820
Two identical instantiations of a template function can be emitted by two TU's
with linkonce_odr linkage without causing duplicate symbols in linker. MSVC
also requires these symbols be in comdat sections. Linux does not require
the symbols in comdat sections to be merged by linker but by default
clang puts them in comdat sections.
If a template kernel is instantiated identically in two TU's. MSVC requires
that them to be in comdat sections, otherwise MSVC linker will diagnose them as
duplicate symbols. However, currently clang does not put instantiated template
kernels in comdat sections, which causes link error for MSVC.
This patch allows putting instantiated template kernels into comdat sections.
Reviewed by: Artem Belevich, Reid Kleckner
Differential Revision: https://reviews.llvm.org/D112492
Previously, the Backend_Emit{Nothing,BC,LL} modes did
not run the LLVM verifier since it is usually added via
the TargetMachine::addPassesToEmitFile method according
to the DisableVerify parameter. This is called from
EmitAssemblyHelper::AddEmitPasses, which is only relevant
for BackendAction-s that require CodeGen.
Note:
* In these particular situations the verifier is added
to the optimization pipeline rather than the codegen
pipeline so that it runs prior to the BC/LL emission
pass.
* This change applies to both the old and the new PMs.
* Because the clang tests use -emit-llvm ubiquitously,
this change will enable the verifier for them.
* A small bug is fixed in emitIFuncDefinition so that
the clang/test/CodeGen/ifunc.c test would pass:
the emitIFuncDefinition incorrectly passed the
GlobalDecl of the IFunc itself to the call to
GetOrCreateLLVMFunction for creating the resolver.
Signed-off-by: Itay Bookstein <ibookstein@gmail.com>
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D113352
The existing CGOpenMPRuntimeAMDGCN and CGOpenMPRuntimeNVPTX classes are
just code bloat. By removing them, the codebase gets a bit cleaner.
Reviewed By: jdoerfert, JonChesterfield, tianshilei1992
Differential Revision: https://reviews.llvm.org/D113421
The existing CGOpenMPRuntimeAMDGCN and CGOpenMPRuntimeNVPTX classes are
just code bloat. By removing them, the codebase gets a bit cleaner.
Reviewed By: jdoerfert, JonChesterfield, tianshilei1992
Differential Revision: https://reviews.llvm.org/D113421
Verify that the resolver exists, that it is a defined
Function, and that its return type matches the ifunc's
type. Add corresponding check to BitcodeReader, change
clang to emit the correct type, and fix tests to comply.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D112349
This reverts commit 121b2252de.
The following code causes a crash in some circumstances:
struct k {
~k() __attribute__((annotate(""))) {}
};
void m() { k(); }
As discussed in:
* https://reviews.llvm.org/D94166
* https://lists.llvm.org/pipermail/llvm-dev/2020-September/145031.html
The GlobalIndirectSymbol class lost most of its meaning in
https://reviews.llvm.org/D109792, which disambiguated getBaseObject
(now getAliaseeObject) between GlobalIFunc and everything else.
In addition, as long as GlobalIFunc is not a GlobalObject and
getAliaseeObject returns GlobalObjects, a GlobalAlias whose aliasee
is a GlobalIFunc cannot currently be modeled properly. Creating
aliases for GlobalIFuncs does happen in the wild (e.g. glibc). In addition,
calling getAliaseeObject on a GlobalIFunc will currently return nullptr,
which is undesirable because it should return the object itself for
non-aliases.
This patch refactors the GlobalIFunc class to inherit directly from
GlobalObject, and removes GlobalIndirectSymbol (while inlining the
relevant parts into GlobalAlias and GlobalIFunc). This allows for
calling getAliaseeObject() on a GlobalIFunc to return the GlobalIFunc
itself, making getAliaseeObject() more consistent and enabling
alias-to-ifunc to be properly modeled in the IR.
I exercised some judgement in the API clients of GlobalIndirectSymbol:
some were 'monomorphized' for GlobalAlias and GlobalIFunc, and
some remained shared (with the type adapted to become GlobalValue).
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D108872
When AnnotateAttr is on a function, AddGlobalAnnotations is only called
in CodeGenModule::EmitGlobalFunctionDefinition which means AnnotateAttr
on function declaration without function body will be ignored.
The patch will move AddGlobalAnnotations to
CodeGenModule::SetFunctionAttributes, so with or without function body,
the AnnotateAttr will get code gen for a function.
It'll help case when AnnotateAttr is on external function, and the
AnnotateAttr will be consumed in IR level.
For example, a pass to collect num of uses for functions with
__attribute((annotate("count_use"))) after optimizations,
As long as there's __attribute((annotate("count_use"))), function with
or without function body should be counted.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D111109
Patch by: python3kgae (Xiang Li)
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.
This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.
The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.
Updating clang's max allowed alignment will come in a future patch.
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D110451
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.
This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.
The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.
Updating clang's max allowed alignment will come in a future patch.
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D110451
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.
This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.
The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.
Updating clang's max allowed alignment will come in a future patch.
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D110451
To avoid using the AST when emitting diagnostics, split the "dontcall"
attribute into "dontcall-warn" and "dontcall-error", and also add the
frontend attribute value as the LLVM attribute value. This gives us all
the information to report diagnostics we need from within the IR (aside
from access to the original source).
One downside is we directly use LLVM's demangler rather than using the
existing Clang diagnostic pretty printing of symbols.
Previous revisions didn't properly declare the new dependencies.
Reviewed By: nickdesaulniers
Differential Revision: https://reviews.llvm.org/D110364
To avoid using the AST when emitting diagnostics, split the "dontcall"
attribute into "dontcall-warn" and "dontcall-error", and also add the
frontend attribute value as the LLVM attribute value. This gives us all
the information to report diagnostics we need from within the IR (aside
from access to the original source).
One downside is we directly use LLVM's demangler rather than using the
existing Clang diagnostic pretty printing of symbols.
Reviewed By: nickdesaulniers
Differential Revision: https://reviews.llvm.org/D110364
(This is a recommit of 3d6f49a569 that should no longer break validation since
bd379915de).
It is a common practice in glibc header to provide an inline redefinition of an
existing function. It is especially the case for fortified function.
Clang currently has an imperfect approach to the problem, using a combination of
trivially recursive function detection and noinline attribute.
Simplify the logic by suffixing these functions by `.inline` during codegen, so
that they are not recognized as builtin by llvm.
After that patch, clang passes all tests from https://github.com/serge-sans-paille/fortify-test-suite
Differential Revision: https://reviews.llvm.org/D109967
It is a common practice in glibc header to provide an inline redefinition of an
existing function. It is especially the case for fortified function.
Clang currently has an imperfect approach to the problem, using a combination of
trivially recursive function detection and noinline attribute.
Simplify the logic by suffixing these functions by `.inline` during codegen, so
that they are not recognized as builtin by llvm.
After that patch, clang passes all tests from https://github.com/serge-sans-paille/fortify-test-suite
Differential Revision: https://reviews.llvm.org/D109967
We previously made all multiversioning resolvers/ifuncs have weak
ODR linkage in IR, since we NEED to emit the whole resolver every time
we see a call, but it is not necessarily the place where all the
definitions live.
HOWEVER, when doing so, we neglected the case where the versions have
internal linkage. This patch ensures we do this, so you don't get weird
behavior with static functions.
This change defines a helper function getOpenCLCompatibleVersion()
inside LangOptions class. The function contains mapping between
C++ for OpenCL versions and their corresponding compatible OpenCL
versions. This mapping function should be updated each time a new
C++ for OpenCL language version is introduced. The helper function
is expected to simplify conditions on OpenCL C and C++ for OpenCL
versions inside compiler code.
Code refactoring performed.
Differential Revision: https://reviews.llvm.org/D108693
The existing code attempting to bitcast from a value in the default globals AS
to i8 addrspace(0)* was triggering an assertion failure in our downstream fork.
I found this while compiling poppler for CHERI-RISC-V (we use AS200 for all
globals). The test case uses AMDGPU since that is one of the in-tree targets
with a non-zero default globals address space.
The new test previously triggered a "Invalid constantexpr bitcast!" assertion
and now correctly generates code with addrspace(1) pointers.
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D105972
Add support for the GNU C style __attribute__((error(""))) and
__attribute__((warning(""))). These attributes are meant to be put on
declarations of functions whom should not be called.
They are frequently used to provide compile time diagnostics similar to
_Static_assert, but which may rely on non-ICE conditions (ie. relying on
compiler optimizations). This is also similar to diagnose_if function
attribute, but can diagnose after optimizations have been run.
While users may instead simply call undefined functions in such cases to
get a linkage failure from the linker, these provide a much more
ergonomic and actionable diagnostic to users and do so at compile time
rather than at link time. Users instead may be able use inline asm .err
directives.
These are used throughout the Linux kernel in its implementation of
BUILD_BUG and BUILD_BUG_ON macros. These macros generally cannot be
converted to use _Static_assert because many of the parameters are not
ICEs. The Linux kernel still needs to be modified to make use of these
when building with Clang; I have a patch that does so I will send once
this feature is landed.
To do so, we create a new IR level Function attribute, "dontcall" (both
error and warning boil down to one IR Fn Attr). Then, similar to calls
to inline asm, we attach a !srcloc Metadata node to call sites of such
attributed callees.
The backend diagnoses these during instruction selection, while we still
know that a call is a call (vs say a JMP that's a tail call) in an arch
agnostic manner.
The frontend then reconstructs the SourceLocation from that Metadata,
and determines whether to emit an error or warning based on the callee's
attribute.
Link: https://bugs.llvm.org/show_bug.cgi?id=16428
Link: https://github.com/ClangBuiltLinux/linux/issues/1173
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D106030
NVPTX does not allow dots in the identifier, so ptxas errors out with
fatal : Parsing error near '.static': syntax error
because it parses .static as a directive. Avoid this problem by using
two underscores, similar to what OpenMP does for outlined functions.
Differential Revision: https://reviews.llvm.org/D108456
Pass a LangAS instead of a target address space to
GetOrCreateLLVMGlobal, to remove a place where the frontend assumes that
target address space 0 is special.
Differential Revision: https://reviews.llvm.org/D108445
- They need to be preserved even if there's no reference within the
device code as the host code may need to initialize them based on the
application logic.
Reviewed By: tra
Differential Revision: https://reviews.llvm.org/D107718
This matches the behavior of GCC.
Patch does not change remapping logic itself, so adding one simple smoke test should be enough.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D107393
Address sanitizer passes may generate call of ASAN bitcode library
functions after bitcode linking in lld, therefore lld cannot add
those symbols since it does not know they will be used later.
To solve this issue, clang emits a reference to a bicode library
function which calls all ASAN functions which need to be
preserved. This basically force all ASAN functions to be
linked in.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D106315
This patch adds a module level metadata flag indicating that the module
was compiled with the `-fopenmp` flag. This will make it easier for
passes like OpenMPOpt to determine if it should be run.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D102361
<string> is currently the highest impact header in a clang+llvm build:
https://commondatastorage.googleapis.com/chromium-browser-clang/llvm-include-analysis.html
One of the most common places this is being included is the APInt.h header, which needs it for an old toString() implementation that returns std::string - an inefficient method compared to the SmallString versions that it actually wraps.
This patch replaces these APInt/APSInt methods with a pair of llvm::toString() helpers inside StringExtras.h, adjusts users accordingly and removes the <string> from APInt.h - I was hoping that more of these users could be converted to use the SmallString methods, but it appears that most end up creating a std::string anyhow. I avoided trying to use the raw_ostream << operators as well as I didn't want to lose having the integer radix explicit in the code.
Differential Revision: https://reviews.llvm.org/D103888
-Wframe-larger-than= is an interesting warning; we can't know the frame
size until PrologueEpilogueInsertion (PEI); very late in the compilation
pipeline.
-Wframe-larger-than= was propagated through CC1 as an -mllvm flag, then
was a cl::opt in LLVM's PEI pass; this meant it was dropped during LTO
and needed to be re-specified via -plugin-opt.
Instead, make it part of the IR proper as a module level attribute,
similar to D103048. Introduce -fwarn-stack-size CC1 option.
Reviewed By: rsmith, qcolombet
Differential Revision: https://reviews.llvm.org/D103928
This implements the 'using enum maybe-qualified-enum-tag ;' part of
1099. It introduces a new 'UsingEnumDecl', subclassed from
'BaseUsingDecl'. Much of the diff is the boilerplate needed to get the
new class set up.
There is one case where we accept ill-formed, but I believe this is
merely an extended case of an existing bug, so consider it
orthogonal. AFAICT in class-scope the c++20 rule is that no 2 using
decls can bring in the same target decl ([namespace.udecl]/8). But we
already accept:
struct A { enum { a }; };
struct B : A { using A::a; };
struct C : B { using A::a;
using B::a; }; // same enumerator
this patch permits mixtures of 'using enum Bob;' and 'using Bob::member;' in the same way.
Differential Revision: https://reviews.llvm.org/D102241
This fixes PR49198: Wrong usage of __dso_handle in user code leads to
a compiler crash.
When Init is an address of the global itself, we need to track it
across RAUW. Otherwise the initializer can be destroyed if the global
is replaced.
Differential Revision: https://reviews.llvm.org/D101156
These actually can be automatically imported from another DLL. (This
works properly as long as the actual implementation of emutls is
linked dynamically from e.g. libgcc; if the implementation comes from
compiler-rt or a statically linked libgcc, it doesn't work as intended.)
This fixes PR50146 and https://github.com/msys2/MINGW-packages/issues/8706
(fixing calling std::call_once in a dynamically linked libstdc++);
since f731839584 the dso_local attribute
on the TLS variable affected the actual generated code for accessing
the emutls variable.
The dso_local attribute on the emutls variable made those accesses to
use 32 bit relative addressing in code, which requires runtime pseudo
relocations in the text section, and breaks entirely if the actual
other variable ends up loaded too far away in the virtual address
space.
Differential Revision: https://reviews.llvm.org/D102970
D88631 added initial support for:
- -mstack-protector-guard=
- -mstack-protector-guard-reg=
- -mstack-protector-guard-offset=
flags, and D100919 extended these to AArch64. Unfortunately, these flags
aren't retained for LTO. Make them module attributes rather than
TargetOptions.
Link: https://github.com/ClangBuiltLinux/linux/issues/1378
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D102742
variables emitted on both host and device side with different addresses
when ODR-used by host function should not cause device side counter-part
to be force emitted.
This fixes the regression caused by https://reviews.llvm.org/D102237
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D102801
This reduces the size of chrome.dll.pdb built with optimizations,
coverage, and line table info from 4,690,210,816 to 2,181,128,192, which
makes it possible to fit under the 4GB limit.
This change can greatly reduce binary size in coverage builds, which do
not need value profiling. IR PGO builds are unaffected. There is a minor
behavior change for frontend PGO.
PGO and coverage both use InstrProfiling to create profile data with
counters. PGO records the address of each function in the __profd_
global. It is used later to map runtime function pointer values back to
source-level function names. Coverage does not appear to use this
information.
Recording the address of every function with code coverage drastically
increases code size. Consider this program:
void foo();
void bar();
inline void inlineMe(int x) {
if (x > 0)
foo();
else
bar();
}
int getVal();
int main() { inlineMe(getVal()); }
With code coverage, the InstrProfiling pass runs before inlining, and it
captures the address of inlineMe in the __profd_ global. This greatly
increases code size, because now the compiler can no longer delete
trivial code.
One downside to this approach is that users of frontend PGO must apply
the -mllvm -enable-value-profiling flag globally in TUs that enable PGO.
Otherwise, some inline virtual method addresses may not be recorded and
will not be able to be promoted. My assumption is that this mllvm flag
is not popular, and most frontend PGO users don't enable it.
Differential Revision: https://reviews.llvm.org/D102818
`clang -fpic -fno-semantic-interposition` may set dso_local on variables for -fpic.
GCC folks consider there are 'address interposition' and 'semantic interposition',
and 'disabling semantic interposition' can optimize function calls but
cannot change variable references to use local aliases
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100483).
This patch removes dso_local for variables in
`clang -fpic -fno-semantic-interposition` mode so that the built shared objects can
work with copy relocations. Building llvm-project tiself with
-fno-semantic-interposition (D102453) should now be safe with trunk Clang.
Example:
```
// a.c
int var;
int *addr() { return var; }
// old: cannot be interposed
movslq .Lvar$local(%rip), %rax
// new: can be interposed
movq var@GOTPCREL(%rip), %rax
movslq (%rax), %rax
```
The local alias lowering for `GlobalVariable`s is kept in case there is a
future option allowing local aliases.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D102583
This patch is the Part-1 (FE Clang) implementation of HW Exception handling.
This new feature adds the support of Hardware Exception for Microsoft Windows
SEH (Structured Exception Handling).
This is the first step of this project; only X86_64 target is enabled in this patch.
Compiler options:
For clang-cl.exe, the option is -EHa, the same as MSVC.
For clang.exe, the extra option is -fasync-exceptions,
plus -triple x86_64-windows -fexceptions and -fcxx-exceptions as usual.
NOTE:: Without the -EHa or -fasync-exceptions, this patch is a NO-DIFF change.
The rules for C code:
For C-code, one way (MSVC approach) to achieve SEH -EHa semantic is to follow
three rules:
* First, no exception can move in or out of _try region., i.e., no "potential
faulty instruction can be moved across _try boundary.
* Second, the order of exceptions for instructions 'directly' under a _try
must be preserved (not applied to those in callees).
* Finally, global states (local/global/heap variables) that can be read
outside of _try region must be updated in memory (not just in register)
before the subsequent exception occurs.
The impact to C++ code:
Although SEH is a feature for C code, -EHa does have a profound effect on C++
side. When a C++ function (in the same compilation unit with option -EHa ) is
called by a SEH C function, a hardware exception occurs in C++ code can also
be handled properly by an upstream SEH _try-handler or a C++ catch(...).
As such, when that happens in the middle of an object's life scope, the dtor
must be invoked the same way as C++ Synchronous Exception during unwinding
process.
Design:
A natural way to achieve the rules above in LLVM today is to allow an EH edge
added on memory/computation instruction (previous iload/istore idea) so that
exception path is modeled in Flow graph preciously. However, tracking every
single memory instruction and potential faulty instruction can create many
Invokes, complicate flow graph and possibly result in negative performance
impact for downstream optimization and code generation. Making all
optimizations be aware of the new semantic is also substantial.
This design does not intend to model exception path at instruction level.
Instead, the proposed design tracks and reports EH state at BLOCK-level to
reduce the complexity of flow graph and minimize the performance-impact on CPP
code under -EHa option.
One key element of this design is the ability to compute State number at
block-level. Our algorithm is based on the following rationales:
A _try scope is always a SEME (Single Entry Multiple Exits) region as jumping
into a _try is not allowed. The single entry must start with a seh_try_begin()
invoke with a correct State number that is the initial state of the SEME.
Through control-flow, state number is propagated into all blocks. Side exits
marked by seh_try_end() will unwind to parent state based on existing
SEHUnwindMap[].
Note side exits can ONLY jump into parent scopes (lower state number).
Thus, when a block succeeds various states from its predecessors, the lowest
State triumphs others. If some exits flow to unreachable, propagation on those
paths terminate, not affecting remaining blocks.
For CPP code, object lifetime region is usually a SEME as SEH _try.
However there is one rare exception: jumping into a lifetime that has Dtor but
has no Ctor is warned, but allowed:
Warning: jump bypasses variable with a non-trivial destructor
In that case, the region is actually a MEME (multiple entry multiple exits).
Our solution is to inject a eha_scope_begin() invoke in the side entry block to
ensure a correct State.
Implementation:
Part-1: Clang implementation described below.
Two intrinsic are created to track CPP object scopes; eha_scope_begin() and eha_scope_end().
_scope_begin() is immediately added after ctor() is called and EHStack is pushed.
So it must be an invoke, not a call. With that it's also guaranteed an
EH-cleanup-pad is created regardless whether there exists a call in this scope.
_scope_end is added before dtor(). These two intrinsics make the computation of
Block-State possible in downstream code gen pass, even in the presence of
ctor/dtor inlining.
Two intrinsic, seh_try_begin() and seh_try_end(), are added for C-code to mark
_try boundary and to prevent from exceptions being moved across _try boundary.
All memory instructions inside a _try are considered as 'volatile' to assure
2nd and 3rd rules for C-code above. This is a little sub-optimized. But it's
acceptable as the amount of code directly under _try is very small.
Part-2 (will be in Part-2 patch): LLVM implementation described below.
For both C++ & C-code, the state of each block is computed at the same place in
BE (WinEHPreparing pass) where all other EH tables/maps are calculated.
In addition to _scope_begin & _scope_end, the computation of block state also
rely on the existing State tracking code (UnwindMap and InvokeStateMap).
For both C++ & C-code, the state of each block with potential trap instruction
is marked and reported in DAG Instruction Selection pass, the same place where
the state for -EHsc (synchronous exceptions) is done.
If the first instruction in a reported block scope can trap, a Nop is injected
before this instruction. This nop is needed to accommodate LLVM Windows EH
implementation, in which the address in IPToState table is offset by +1.
(note the purpose of that is to ensure the return address of a call is in the
same scope as the call address.
The handler for catch(...) for -EHa must handle HW exception. So it is
'adjective' flag is reset (it cannot be IsStdDotDot (0x40) that only catches
C++ exceptions).
Suppress push/popTerminate() scope (from noexcept/noTHrow) so that HW
exceptions can be passed through.
Original llvm-dev [RFC] discussions can be found in these two threads below:
https://lists.llvm.org/pipermail/llvm-dev/2020-March/140541.htmlhttps://lists.llvm.org/pipermail/llvm-dev/2020-April/141338.html
Differential Revision: https://reviews.llvm.org/D80344/new/
As it was discovered in post-commit feedback
for 0aa0458f14,
we handle thunks incorrectly, and end up annotating
their this/return with attributes that are valid
for their callees, not for thunks themselves.
While it would be good to fix this properly,
and keep annotating them on thunks,
i've tried doing that in https://reviews.llvm.org/D100388
with little success, and the patch is stuck for a month now.
So for now, as a stopgap measure, subj.
Currently clang does not emit device template variables
instantiated only in host functions, however, nvcc is
able to do that:
https://godbolt.org/z/fneEfferY
This patch fixes this issue by refactoring and extending
the existing mechanism for emitting static device
var ODR-used by host only. Basically clang records
device variables ODR-used by host code and force
them to be emitted in device compilation. The existing
mechanism makes sure these device variables ODR-used
by host code are added to llvm.compiler-used, therefore
they are guaranteed not to be deleted.
It also fixes non-ODR-use of static device variable by host code
causing static device variable to be emitted and registered,
which should not.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D102237
This patch fixes various issues with our prior `declare target` handling
and extends it to support `omp begin declare target` as well.
This started with PR49649 in mind, trying to provide a way for users to
avoid the "ref" global use introduced for globals with internal linkage.
From there it went down the rabbit hole, e.g., all variables, even
`nohost` ones, were emitted into the device code so it was impossible to
determine if "ref" was needed late in the game (based on the name only).
To make it really useful, `begin declare target` was needed as it can
carry the `device_type`. Not emitting variables eagerly had a ripple
effect. Finally, the precedence of the (explicit) declare target list
items needed to be taken into account, that meant we cannot just look
for any declare target attribute to make a decision. This caused the
handling of functions to require fixup as well.
I tried to clean up things while I was at it, e.g., we should not "parse
declarations and defintions" as part of OpenMP parsing, this will always
break at some point. Instead, we keep track what region we are in and
act on definitions and declarations instead, this is what we do for
declare variant and other begin/end directives already.
Highlights:
- new diagnosis for restrictions specificed in the standard,
- delayed emission of globals not mentioned in an explicit
list of a declare target,
- omission of `nohost` globals on the host and `host` globals on the
device,
- no explicit parsing of declarations in-between `omp [begin] declare
variant` and the corresponding end anymore, regular parsing instead,
- precedence for explicit mentions in `declare target` lists over
implicit mentions in the declaration-definition-seq, and
- `omp allocate` declarations will now replace an earlier emitted
global, if necessary.
---
Notes:
The patch is larger than I hoped but it turns out that most changes do
on their own lead to "inconsistent states", which seem less desirable
overall.
After working through this I feel the standard should remove the
explicit declare target forms as the delayed emission is horrible.
That said, while we delay things anyway, it seems to me we check too
often for the current status even though that is often not sufficient to
act upon. There seems to be a lot of duplication that can probably be
trimmed down. Eagerly emitting some things seems pretty weak as an
argument to keep so much logic around.
---
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D101030
This implements the flag proposed in RFC
http://lists.llvm.org/pipermail/cfe-dev/2020-August/066437.html.
The goal is to add a way to override the default target C++ ABI through a
compiler flag. This makes it easier to test and transition between different
C++ ABIs through compile flags rather than build flags.
In this patch:
- Store -fc++-abi= in a LangOpt. This isn't stored in a CodeGenOpt because
there are instances outside of codegen where Clang needs to know what the
ABI is (particularly through ASTContext::createCXXABI), and we should be
able to override the target default if the flag is provided at that point.
- Expose the existing ABIs in TargetCXXABI as values that can be passed
through this flag.
- Create a .def file for these ABIs to make it easier to check flag values.
- Add an error for diagnosing bad ABI flag values.
Differential Revision: https://reviews.llvm.org/D85802
The use of llvm::sort causes periodic failures on the bot with EXPENSIVE_CHECKS enabled,
as the regular sort pre-shuffles the array in the expensive checks mode, leading to a
non-deterministic test result which causes the CodeGenCXX/attr-cpuspecific-outoflinedefs.cpp
testcase to fail on the bot (http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA-expensive/).
Default address space (applies when no explicit address space was
specified) maps to generic (4) address space.
Added SYCL named address spaces `sycl_global`, `sycl_local` and
`sycl_private` defined as sub-sets of the default address space.
Static variables without address space now reside in global address
space when compile for SPIR target, unless they have an explicit address
space qualifier in source code.
Differential Revision: https://reviews.llvm.org/D89909
The Linux kernel objtool diagnostic `call without frame pointer save/setup`
arise in multiple instrumentation passes (asan/tsan/gcov). With the mechanism
introduced in D100251, it's trivial to respect the command line
-m[no-]omit-leaf-frame-pointer/-f[no-]omit-frame-pointer, so let's do it.
Fix: https://github.com/ClangBuiltLinux/linux/issues/1236 (tsan)
Fix: https://github.com/ClangBuiltLinux/linux/issues/1238 (asan)
Also document the function attribute "frame-pointer" which is long overdue.
Differential Revision: https://reviews.llvm.org/D101016
On ELF targets, if a function has uwtable or personality, or does not have
nounwind (`needsUnwindTableEntry`), it marks that `.eh_frame` is needed in the module.
Then, a function gets `.eh_frame` if `needsUnwindTableEntry` or `-g[123]` is specified.
(i.e. If -g[123], every function gets `.eh_frame`.
This behavior is strange but that is the status quo on GCC and Clang.)
Let's take asan as an example. Other sanitizers are similar.
`asan.module_[cd]tor` has no attribute. `needsUnwindTableEntry` returns true,
so every function gets `.eh_frame` if `-g[123]` is specified.
This is the root cause that
`-fno-exceptions -fno-asynchronous-unwind-tables -g` produces .debug_frame
while
`-fno-exceptions -fno-asynchronous-unwind-tables -g -fsanitize=address` produces .eh_frame.
This patch
* sets the nounwind attribute on sanitizer module ctor/dtor.
* let Clang emit a module flag metadata "uwtable" for -fasynchronous-unwind-tables. If "uwtable" is set, sanitizer module ctor/dtor additionally get the uwtable attribute.
The "uwtable" mechanism is generic: synthesized functions not cloned/specialized
from existing ones should consider `Function::createWithDefaultAttr` instead of
`Function::create` if they want to get some default attributes which
have more of module semantics.
Other candidates: "frame-pointer" (https://github.com/ClangBuiltLinux/linux/issues/955https://github.com/ClangBuiltLinux/linux/issues/1238), dso_local, etc.
Differential Revision: https://reviews.llvm.org/D100251
As reported in PR50025, sometimes we would end up not emitting functions
needed by inline multiversioned variants. This is because we typically
use the 'deferred decl' mechanism to emit these. However, the variants
are emitted after that typically happens. This fixes that by ensuring
we re-run deferred decls after this happens. Also, the multiversion
emission is done recursively to ensure that MV functions that require
other MV functions to be emitted get emitted.
The original issue is caused by the fact that the variable is allocated
with incorrect type i1 instead of i8. This causes the bitcasting of the
declaration to i8 type and the bitcast expression does not match the
original variable.
To fix the problem, the UndefValue initializer and the original
variable should be emitted with type i8, not i1.
Differential Revision: https://reviews.llvm.org/D99297
This reverts commit 809a1e0ffd.
Mach-O doesn't support dso_local and this change broke XNU because of the use of dso_local.
Differential Revision: https://reviews.llvm.org/D98458
`CodeGenFunction::EmitRuntimeCall` automatically sets the right calling
convention for the callee so we can avoid setting it ourselves.
As requested in https://reviews.llvm.org/D98411
Reviewed by: anastasia
Differential Revision: https://reviews.llvm.org/D98705
`__translate_sampler_initializer` has a calling convention of
`spir_func`, but clang generated calls to it using the default CC.
Instruction Combining was lowering these mismatching calling conventions
to `store i1* undef` which itself was subsequently lowered to a trap
instruction by simplifyCFG resulting in runtime `SIGILL`
There are arguably two bugs here: but whether there's any wisdom in
converting an obviously invalid call into a runtime crash over aborting
with a sensible error message will require further discussion. So for
now it's enough to set the right calling convention on the runtime
helper.
Reviewed By: svenh, bader
Differential Revision: https://reviews.llvm.org/D98411
D96109 added support for unique internal linkage names for both internal
linkage functions and global variables. There was a lot of discussion on how to
get the demangling right for functions but I completely missed the point that
demanglers do not support suffixes for global vars. For example:
$ c++filt _ZL3foo
foo
$ c++filt _ZL3foo.uniq.123
_ZL3foo.uniq.123
The demangling for functions works as expected.
I am not sure of the impact of this. I don't understand how debuggers and other
tools depend on the correctness of global variable demangling so I am
pre-emptively disabling it until we can get the demangling support added.
Importantly, uniquefying global variables is not needed right now as we do not
do profile attribution to global vars based on sampling. It was added for
completeness and so this feature is not exactly missed.
Differential Revision: https://reviews.llvm.org/D98392
The option -funique-internal-linkage-names was added in D73307 and D78243 as a
LLVM early pass to insert a unique suffix to internal linkage functions and
vars. The unique suffix was the hash of the module path. However, we found
that this can be done more cleanly in clang early and the fixes that need to
be done later can be completely avoided. The fixes in particular are trying
to modify the DW_AT_linkage_name and finding the right place to insert the
pass.
This patch ressurects the original implementation proposed in D73307 which
was reviewed and then ditched in favor of the pass based approach.
Differential Revision: https://reviews.llvm.org/D96109
explicitly emitting retainRV or claimRV calls in the IR
This reapplies ed4718eccb, which was reverted
because it was causing a miscompile. The bug that was causing the miscompile
has been fixed in 75805dce5f.
Original commit message:
Background:
This fixes a longstanding problem where llvm breaks ARC's autorelease
optimization (see the link below) by separating calls from the marker
instructions or retainRV/claimRV calls. The backend changes are in
https://reviews.llvm.org/D92569.
https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-autoreleasereturnvalue
What this patch does to fix the problem:
- The front-end adds operand bundle "clang.arc.attachedcall" to calls,
which indicates the call is implicitly followed by a marker
instruction and an implicit retainRV/claimRV call that consumes the
call result. In addition, it emits a call to
@llvm.objc.clang.arc.noop.use, which consumes the call result, to
prevent the middle-end passes from changing the return type of the
called function. This is currently done only when the target is arm64
and the optimization level is higher than -O0.
- ARC optimizer temporarily emits retainRV/claimRV calls after the calls
with the operand bundle in the IR and removes the inserted calls after
processing the function.
- ARC contract pass emits retainRV/claimRV calls after the call with the
operand bundle. It doesn't remove the operand bundle on the call since
the backend needs it to emit the marker instruction. The retainRV and
claimRV calls are emitted late in the pipeline to prevent optimization
passes from transforming the IR in a way that makes it harder for the
ARC middle-end passes to figure out the def-use relationship between
the call and the retainRV/claimRV calls (which is the cause of
PR31925).
- The function inliner removes an autoreleaseRV call in the callee if
nothing in the callee prevents it from being paired up with the
retainRV/claimRV call in the caller. It then inserts a release call if
claimRV is attached to the call since autoreleaseRV+claimRV is
equivalent to a release. If it cannot find an autoreleaseRV call, it
tries to transfer the operand bundle to a function call in the callee.
This is important since the ARC optimizer can remove the autoreleaseRV
returning the callee result, which makes it impossible to pair it up
with the retainRV/claimRV call in the caller. If that fails, it simply
emits a retain call in the IR if retainRV is attached to the call and
does nothing if claimRV is attached to it.
- SCCP refrains from replacing the return value of a call with a
constant value if the call has the operand bundle. This ensures the
call always has at least one user (the call to
@llvm.objc.clang.arc.noop.use).
- This patch also fixes a bug in replaceUsesOfNonProtoConstant where
multiple operand bundles of the same kind were being added to a call.
Future work:
- Use the operand bundle on x86-64.
- Fix the auto upgrader to convert call+retainRV/claimRV pairs into
calls with the operand bundles.
rdar://71443534
Differential Revision: https://reviews.llvm.org/D92808
This caused miscompiles of Chromium tests for iOS due clobbering of live
registers. See discussion on the code review for details.
> Background:
>
> This fixes a longstanding problem where llvm breaks ARC's autorelease
> optimization (see the link below) by separating calls from the marker
> instructions or retainRV/claimRV calls. The backend changes are in
> https://reviews.llvm.org/D92569.
>
> https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-autoreleasereturnvalue
>
> What this patch does to fix the problem:
>
> - The front-end adds operand bundle "clang.arc.attachedcall" to calls,
> which indicates the call is implicitly followed by a marker
> instruction and an implicit retainRV/claimRV call that consumes the
> call result. In addition, it emits a call to
> @llvm.objc.clang.arc.noop.use, which consumes the call result, to
> prevent the middle-end passes from changing the return type of the
> called function. This is currently done only when the target is arm64
> and the optimization level is higher than -O0.
>
> - ARC optimizer temporarily emits retainRV/claimRV calls after the calls
> with the operand bundle in the IR and removes the inserted calls after
> processing the function.
>
> - ARC contract pass emits retainRV/claimRV calls after the call with the
> operand bundle. It doesn't remove the operand bundle on the call since
> the backend needs it to emit the marker instruction. The retainRV and
> claimRV calls are emitted late in the pipeline to prevent optimization
> passes from transforming the IR in a way that makes it harder for the
> ARC middle-end passes to figure out the def-use relationship between
> the call and the retainRV/claimRV calls (which is the cause of
> PR31925).
>
> - The function inliner removes an autoreleaseRV call in the callee if
> nothing in the callee prevents it from being paired up with the
> retainRV/claimRV call in the caller. It then inserts a release call if
> claimRV is attached to the call since autoreleaseRV+claimRV is
> equivalent to a release. If it cannot find an autoreleaseRV call, it
> tries to transfer the operand bundle to a function call in the callee.
> This is important since the ARC optimizer can remove the autoreleaseRV
> returning the callee result, which makes it impossible to pair it up
> with the retainRV/claimRV call in the caller. If that fails, it simply
> emits a retain call in the IR if retainRV is attached to the call and
> does nothing if claimRV is attached to it.
>
> - SCCP refrains from replacing the return value of a call with a
> constant value if the call has the operand bundle. This ensures the
> call always has at least one user (the call to
> @llvm.objc.clang.arc.noop.use).
>
> - This patch also fixes a bug in replaceUsesOfNonProtoConstant where
> multiple operand bundles of the same kind were being added to a call.
>
> Future work:
>
> - Use the operand bundle on x86-64.
>
> - Fix the auto upgrader to convert call+retainRV/claimRV pairs into
> calls with the operand bundles.
>
> rdar://71443534
>
> Differential Revision: https://reviews.llvm.org/D92808
This reverts commit ed4718eccb.
`GetAddrOfGlobalTemporary` previously tried to emit the initializer of
a global temporary before updating the global temporary map. Emitting the
initializer could recurse back into `GetAddrOfGlobalTemporary` for the same
temporary, resulting in an infinite recursion.
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D97733
Currently clang uses stub function to launch kernel. This is inconvenient
to interop with C++ programs since the stub function has different name
as kernel, which is required by ROCm debugger.
This patch emits a variable symbol which has the same name as the kernel
and uses it to register and launch the kernel. This allows C++ program to
launch a kernel by using the original kernel name.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D86376
For ELF targets, GCC 11 will set SHF_GNU_RETAIN on the section of a
`__attribute__((retain))` function/variable to prevent linker garbage
collection. (See AttrDocs.td for the linker support).
This patch adds `retain` functions/variables to the `llvm.used` list, which has
the desired linker GC semantics. Note: `retain` does not imply `used`,
so an unused function/variable can be dropped by Sema.
Before 'retain' was introduced, previous ELF solutions require inline asm or
linker tricks, e.g. `asm volatile(".reloc 0, R_X86_64_NONE, target");`
(architecture dependent) or define a non-local symbol in the section and use
`ld -u`. There was no elegant source-level solution.
With D97448, `__attribute__((retain))` will set `SHF_GNU_RETAIN` on ELF targets.
Differential Revision: https://reviews.llvm.org/D97447
An global value in the `llvm.used` list does not have GC root semantics on ELF targets.
This will be changed in a subsequent backend patch.
Change some `llvm.used` in the ELF code path to use `llvm.compiler.used` to
prevent undesired GC root semantics.
Change one extern "C" alias (due to `__attribute__((used))` in extern "C") to use `llvm.compiler.used` on all targets.
GNU ld has a rule "`__start_/__stop_` references from a live input section retain the associated C identifier name sections",
which LLD may drop entirely (currently refined to exclude SHF_LINK_ORDER/SHF_GROUP) in a future release (the rule makes it clumsy to GC metadata sections; D96914 added a way to try the potential future behavior).
For `llvm.used` global values defined in a C identifier name section, keep using `llvm.used` so that
the future LLD change will not affect them.
rnk kindly categorized the changes:
```
ObjC/blocks: this wants GC root semantics, since ObjC mainly runs on Mac.
MS C++ ABI stuff: wants GC root semantics, no change
OpenMP: unsure, but GC root semantics probably don't hurt
CodeGenModule: affected in this patch to *not* use GC root semantics so that __attribute__((used)) behavior remains the same on ELF, plus two other minor use cases that don't want GC semantics
Coverage: Probably want GC root semantics
CGExpr.cpp: refers to LTO, wants GC root
CGDeclCXX.cpp: one is MS ABI specific, so yes GC root, one is some other C++ init functionality, which should form GC roots (C++ initializers can have side effects and must run)
CGDecl.cpp: Changed in this patch for __attribute__((used))
```
Differential Revision: https://reviews.llvm.org/D97446
For -fgpu-rdc mode, static device vars in different TU's may have the same name.
To support accessing file-scope static device variables in host code, we need to give them
a distinct name and external linkage. This can be done by postfixing each static device variable with
a distinct CUID (Compilation Unit ID) hash.
Since the static device variables have different name across compilation units, now we let
them have external linkage so that they can be looked up by the runtime.
Reviewed by: Artem Belevich, and Jon Chesterfield
Differential Revision: https://reviews.llvm.org/D85223
Currently managed variables are emitted as undefined symbols, which
causes difficulty for diagnosing undefined symbols for non-managed
variables.
This patch transforms managed variables in device compilation so that
they can be emitted as normal variables.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D96195
This patch responds to a comment from @vitalybuka in D96203: suggestion to
do the change incrementally, and start by modifying this file name. I modified
the file name and made the other changes that follow from that rename.
Reviewers: vitalybuka, echristo, MaskRay, jansvoboda11, aaron.ballman
Differential Revision: https://reviews.llvm.org/D96974
This allows the option to affect the LTO output. Module::Max helps to
generate debug info for all modules in the same format.
Differential Revision: https://reviews.llvm.org/D96597
explicitly emitting retainRV or claimRV calls in the IR
Background:
This fixes a longstanding problem where llvm breaks ARC's autorelease
optimization (see the link below) by separating calls from the marker
instructions or retainRV/claimRV calls. The backend changes are in
https://reviews.llvm.org/D92569.
https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-autoreleasereturnvalue
What this patch does to fix the problem:
- The front-end adds operand bundle "clang.arc.attachedcall" to calls,
which indicates the call is implicitly followed by a marker
instruction and an implicit retainRV/claimRV call that consumes the
call result. In addition, it emits a call to
@llvm.objc.clang.arc.noop.use, which consumes the call result, to
prevent the middle-end passes from changing the return type of the
called function. This is currently done only when the target is arm64
and the optimization level is higher than -O0.
- ARC optimizer temporarily emits retainRV/claimRV calls after the calls
with the operand bundle in the IR and removes the inserted calls after
processing the function.
- ARC contract pass emits retainRV/claimRV calls after the call with the
operand bundle. It doesn't remove the operand bundle on the call since
the backend needs it to emit the marker instruction. The retainRV and
claimRV calls are emitted late in the pipeline to prevent optimization
passes from transforming the IR in a way that makes it harder for the
ARC middle-end passes to figure out the def-use relationship between
the call and the retainRV/claimRV calls (which is the cause of
PR31925).
- The function inliner removes an autoreleaseRV call in the callee if
nothing in the callee prevents it from being paired up with the
retainRV/claimRV call in the caller. It then inserts a release call if
claimRV is attached to the call since autoreleaseRV+claimRV is
equivalent to a release. If it cannot find an autoreleaseRV call, it
tries to transfer the operand bundle to a function call in the callee.
This is important since the ARC optimizer can remove the autoreleaseRV
returning the callee result, which makes it impossible to pair it up
with the retainRV/claimRV call in the caller. If that fails, it simply
emits a retain call in the IR if retainRV is attached to the call and
does nothing if claimRV is attached to it.
- SCCP refrains from replacing the return value of a call with a
constant value if the call has the operand bundle. This ensures the
call always has at least one user (the call to
@llvm.objc.clang.arc.noop.use).
- This patch also fixes a bug in replaceUsesOfNonProtoConstant where
multiple operand bundles of the same kind were being added to a call.
Future work:
- Use the operand bundle on x86-64.
- Fix the auto upgrader to convert call+retainRV/claimRV pairs into
calls with the operand bundles.
rdar://71443534
Differential Revision: https://reviews.llvm.org/D92808
Signed prefix is removed and the single word spelling is
printed for the scalar types.
Tags: #clang
Differential Revision: https://reviews.llvm.org/D96161
Pipe element type spelling for arg info metadata
should follow the same behavior as normal type spelling.
We should only use the canonical type spelling in the
base type field.
This patch also removed duplication in type handling.
Tags: #clang
Differential Revision: https://reviews.llvm.org/D96151
For -fgpu-rdc, shadow variables should not be internalized, otherwise
they cannot be accessed by other TUs. This is necessary because
the shadow variable of external device variables are always
emitted as undefined symbols, which need to resolve to a global
symbols.
Managed variables need to be emitted as undefined symbols
in device compilations.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D95901
Extract registering device variable to CUDA runtime codegen function since it
will be called in multiple places.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D95558
Normally, Clang will not make dllimport functions available for inlining
if they reference non-imported symbols, as this can lead to confusing
link errors. But if the function is marked always_inline, the user
presumably knows what they're doing and the attribute should be honored.
Differential revision: https://reviews.llvm.org/D95673
This change implements support for applying profile instrumentation
only to selected files or functions. The implementation uses the
sanitizer special case list format to select which files and functions
to instrument, and relies on the new noprofile IR attribute to exclude
functions from instrumentation.
Differential Revision: https://reviews.llvm.org/D94820
This change implements support for applying profile instrumentation
only to selected files or functions. The implementation uses the
sanitizer special case list format to select which files and functions
to instrument, and relies on the new noprofile IR attribute to exclude
functions from instrumentation.
Differential Revision: https://reviews.llvm.org/D94820
Most of CGExprConstant.cpp is using the CharUnits abstraction
and is using getCharWidth() (directly of indirectly) when converting
between size of a char and size in bits. This patch is making that
abstraction more consistent by adding CharTy to the CodeGenTypeCache
(honoring getCharWidth() when mapping from char to LLVM IR types,
instead of using Int8Ty directly).
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D94979
This patch implements codegen for __managed__ variable attribute for HIP.
Diagnostics will be added later.
Differential Revision: https://reviews.llvm.org/D94814
Move nomerge attribute from function declaration/definition to callsites to
allow virtual function calls attach the attribute.
Differential Revision: https://reviews.llvm.org/D94537
ELF -fno-pic sets dso_local on a function declaration to allow direct accesses
when taking its address (similar to a data symbol). The emitted code follows the
traditional GCC/Clang -fno-pic behavior: an absolute relocation is produced.
If the function is not defined in the executable, a canonical PLT entry will be
needed at link time. This is similar to a copy relocation and is incompatible
with (-Bsymbolic or --dynamic-list linked shared objects / protected symbols in
a shared object).
This patch gives -fno-pic code a way to avoid such a canonical PLT entry.
The FIXME was about a generalization for -fpie -mpie-copy-relocations (now -fpie
-fdirect-access-external-data). While we could set dso_local to avoid GOT when
taking the address of a function declaration (there is an ignorable difference
about R_386_PC32 vs R_386_PLT32 on i386), it likely does not provide any benefit
and can just cause trouble, so we don't make the generalization.
D92633 added -f[no-]direct-access-external-data to supersede -m[no-]pie-copy-relocations.
(The option works for -fpie but is a no-op for -fno-pic and -fpic.)
This patch makes -fno-pic -fno-direct-access-external-data drop dso_local from
global variable declarations. This usually causes the backend to emit a GOT
indirection for external data access. With a GOT relocation, the subsequent
-no-pie link will not have copy relocation even if the data symbol turns out to
be defined by a shared object.
Differential Revision: https://reviews.llvm.org/D92714
GCC r218397 "x86-64: Optimize access to globals in PIE with copy reloc" made
-fpie code emit R_X86_64_PC32 to reference external data symbols by default.
Clang adopted -mpie-copy-relocations D19996 as a flexible alternative.
The name -mpie-copy-relocations can be improved [1] and does not capture the
idea that this option can apply to -fno-pic and -fpic [2], so this patch
introduces -f[no-]direct-access-external-data and makes -mpie-copy-relocations
their aliases for compatibility.
[1]
For
```
extern int var;
int get() { return var; }
```
if var is defined in another translation unit in the link unit, there is no copy
relocation.
[2]
-fno-pic -fno-direct-access-external-data is useful to avoid copy relocations.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65888
If a shared object is linked with -Bsymbolic or --dynamic-list and exports a
data symbol, normally the data symbol cannot be accessed by -fno-pic code
(because by default an absolute relocation is produced which will lead to a copy
relocation). -fno-direct-access-external-data can prevent copy relocations.
-fpic -fdirect-access-external-data can avoid GOT indirection. This is like the
undefined counterpart of -fno-semantic-interposition. However, the user should
define var in another translation unit and link with -Bsymbolic or
--dynamic-list, otherwise the linker will error in a -shared link. Generally
the user has better tools for their goal but I want to mention that this
combination is valid.
On COFF, the behavior is like always -fdirect-access-external-data.
`__declspec(dllimport)` is needed to enable indirect access.
There is currently no plan to affect non-ELF behaviors or -fpic behaviors.
-fno-pic -fno-direct-access-external-data will be implemented in the subsequent patch.
GCC feature request https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98112
Reviewed By: tmsriram
Differential Revision: https://reviews.llvm.org/D92633
The idea is that the CC1 default for ELF should set dso_local on default
visibility external linkage definitions in the default -mrelocation-model pic
mode (-fpic/-fPIC) to match COFF/Mach-O and make output IR similar.
The refactoring is made available by 2820a2ca3a.
Currently only x86 supports local aliases. We move the decision to the driver.
There are three CC1 states:
* -fsemantic-interposition: make some linkages interposable and make default visibility external linkage definitions dso_preemptable.
* (default): selected if the target supports .Lfoo$local: make default visibility external linkage definitions dso_local
* -fhalf-no-semantic-interposition: if neither option is set or the target does not support .Lfoo$local: like -fno-semantic-interposition but local aliases are not used. So references can be interposed if not optimized out.
Add -fhalf-no-semantic-interposition to a few tests using the half-based semantic interposition behavior.
* static relocation model: always
* other relocation models: if isStrongDefinitionForLinker
This will make LLVM IR emitted for COFF/Mach-O and executable ELF similar.
This simplifies TargetMachine::shouldAssumeDSOLocal and and gives frontend the
decision to use dso_local. For LLVM synthesized functions/globals, they may lose
inferred dso_local but such optimizations are probably not very useful.
Note: the hasComdat() condition in canBenefitFromLocalAlias (D77429) may be dead now.
(llvm/CodeGen/X86/semantic-interposition-comdat.ll)
(Investigate whether we need test coverage when Fuchsia C++ ABI is clearer)
Clang FE currently has hot/cold function attribute. But we only have
cold function attribute in LLVM IR.
This patch adds support of hot function attribute to LLVM IR. This
attribute will be used in setting function section prefix/suffix.
Currently .hot and .unlikely suffix only are added in PGO (Sample PGO)
compilation (through isFunctionHotInCallGraph and
isFunctionColdInCallGraph).
This patch changes the behavior. The new behavior is:
(1) If the user annotates a function as hot or isFunctionHotInCallGraph
is true, this function will be marked as hot. Otherwise,
(2) If the user annotates a function as cold or
isFunctionColdInCallGraph is true, this function will be marked as
cold.
The changes are:
(1) user annotated function attribute will used in setting function
section prefix/suffix.
(2) hot attribute overwrites profile count based hotness.
(3) profile count based hotness overwrite user annotated cold attribute.
The intention for these changes is to provide the user a way to mark
certain function as hot in cases where training input is hard to cover
all the hot functions.
Differential Revision: https://reviews.llvm.org/D92493
This patch adds the functionality to compare BFI counts with real
profile
counts right after reading the profile. It will print remarks under
-Rpass-analysis=pgo, or the internal option -pass-remarks-analysis=pgo.
Differential Revision: https://reviews.llvm.org/D91813
PPCMCInstLower does not actually call shouldAssumeDSOLocal for ppc32 so this is dead.
Actually Clang ppc32 does produce a pair of absolute relocations which match GCC.
This also fixes a comment (R_PPC_COPY and R_PPC64_COPY do exist).
shouldRTTIBeUnique() returns false for iOS64CXXABI, which causes
RTTI objects to be emitted hidden. Update two tests that didn't
expect this to happen for the default triple.
Also rename iOS64CXXABI to AppleARM64CXXABI, since it's used for
arm64-apple-macos triples too.
Part of PR46644.
Differential Revision: https://reviews.llvm.org/D91904
Ensure that the DSO Locality of the globals in the IR is derived from
their final visibility when using -fvisibility-from-dllstorageclass.
To accomplish this we reset the DSO locality of globals (before
setting their visibility from their dllstorageclass) at the end of
IRGen in Clang. This removes any effects that visibility options or
annotations may have had on the DSO locality.
The resulting DSO locality of the globals will be pessimistic
w.r.t. to the normal compiler IRGen.
Differential Revision: https://reviews.llvm.org/D91779
Tom Honermann