This patch introduces a new pass that computes the safe point to insert the
prologue and epilogue of the function.
The interest is to find safe points that are cheaper than the entry and exits
blocks.
As an example and to avoid regressions to be introduce, this patch also
implements the required bits to enable the shrink-wrapping pass for AArch64.
** Context **
Currently we insert the prologue and epilogue of the method/function in the
entry and exits blocks. Although this is correct, we can do a better job when
those are not immediately required and insert them at less frequently executed
places.
The job of the shrink-wrapping pass is to identify such places.
** Motivating example **
Let us consider the following function that perform a call only in one branch of
a if:
define i32 @f(i32 %a, i32 %b) {
%tmp = alloca i32, align 4
%tmp2 = icmp slt i32 %a, %b
br i1 %tmp2, label %true, label %false
true:
store i32 %a, i32* %tmp, align 4
%tmp4 = call i32 @doSomething(i32 0, i32* %tmp)
br label %false
false:
%tmp.0 = phi i32 [ %tmp4, %true ], [ %a, %0 ]
ret i32 %tmp.0
}
On AArch64 this code generates (removing the cfi directives to ease
readabilities):
_f: ; @f
; BB#0:
stp x29, x30, [sp, #-16]!
mov x29, sp
sub sp, sp, #16 ; =16
cmp w0, w1
b.ge LBB0_2
; BB#1: ; %true
stur w0, [x29, #-4]
sub x1, x29, #4 ; =4
mov w0, wzr
bl _doSomething
LBB0_2: ; %false
mov sp, x29
ldp x29, x30, [sp], #16
ret
With shrink-wrapping we could generate:
_f: ; @f
; BB#0:
cmp w0, w1
b.ge LBB0_2
; BB#1: ; %true
stp x29, x30, [sp, #-16]!
mov x29, sp
sub sp, sp, #16 ; =16
stur w0, [x29, #-4]
sub x1, x29, #4 ; =4
mov w0, wzr
bl _doSomething
add sp, x29, #16 ; =16
ldp x29, x30, [sp], #16
LBB0_2: ; %false
ret
Therefore, we would pay the overhead of setting up/destroying the frame only if
we actually do the call.
** Proposed Solution **
This patch introduces a new machine pass that perform the shrink-wrapping
analysis (See the comments at the beginning of ShrinkWrap.cpp for more details).
It then stores the safe save and restore point into the MachineFrameInfo
attached to the MachineFunction.
This information is then used by the PrologEpilogInserter (PEI) to place the
related code at the right place. This pass runs right before the PEI.
Unlike the original paper of Chow from PLDI’88, this implementation of
shrink-wrapping does not use expensive data-flow analysis and does not need hack
to properly avoid frequently executed point. Instead, it relies on dominance and
loop properties.
The pass is off by default and each target can opt-in by setting the
EnableShrinkWrap boolean to true in their derived class of TargetPassConfig.
This setting can also be overwritten on the command line by using
-enable-shrink-wrap.
Before you try out the pass for your target, make sure you properly fix your
emitProlog/emitEpilog/adjustForXXX method to cope with basic blocks that are not
necessarily the entry block.
** Design Decisions **
1. ShrinkWrap is its own pass right now. It could frankly be merged into PEI but
for debugging and clarity I thought it was best to have its own file.
2. Right now, we only support one save point and one restore point. At some
point we can expand this to several save point and restore point, the impacted
component would then be:
- The pass itself: New algorithm needed.
- MachineFrameInfo: Hold a list or set of Save/Restore point instead of one
pointer.
- PEI: Should loop over the save point and restore point.
Anyhow, at least for this first iteration, I do not believe this is interesting
to support the complex cases. We should revisit that when we motivating
examples.
Differential Revision: http://reviews.llvm.org/D9210
<rdar://problem/3201744>
llvm-svn: 236507
[DebugInfo] Add debug locations to constant SD nodes
This adds debug location to constant nodes of Selection DAG and updates
all places that create constants to pass debug locations
(see PR13269).
Can't guarantee that all locations are correct, but in a lot of cases choice
is obvious, so most of them should be. At least all tests pass.
Tests for these changes do not cover everything, instead just check it for
SDNodes, ARM and AArch64 where it's easy to get incorrect locations on
constants.
This is not complete fix as FastISel contains workaround for wrong debug
locations, which drops locations from instructions on processing constants,
but there isn't currently a way to use debug locations from constants there
as llvm::Constant doesn't cache it (yet). Although this is a bit different
issue, not directly related to these changes.
Differential Revision: http://reviews.llvm.org/D9084
llvm-svn: 235989
This adds debug location to constant nodes of Selection DAG and updates
all places that create constants to pass debug locations
(see PR13269).
Can't guarantee that all locations are correct, but in a lot of cases choice
is obvious, so most of them should be. At least all tests pass.
Tests for these changes do not cover everything, instead just check it for
SDNodes, ARM and AArch64 where it's easy to get incorrect locations on
constants.
This is not complete fix as FastISel contains workaround for wrong debug
locations, which drops locations from instructions on processing constants,
but there isn't currently a way to use debug locations from constants there
as llvm::Constant doesn't cache it (yet). Although this is a bit different
issue, not directly related to these changes.
Differential Revision: http://reviews.llvm.org/D9084
llvm-svn: 235977
Summary:
MSP430 doesn't seem to have any additional constraints. Therefore remove
the target hook.
No functional change intended.
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D8208
llvm-svn: 235003
per-function subtarget.
Currently, code-gen passes the default or generic subtarget to the constructors
of MCInstPrinter subclasses (see LLVMTargetMachine::addPassesToEmitFile), which
enables some targets (AArch64, ARM, and X86) to change their instprinter's
behavior based on the subtarget feature bits. Since the backend can now use
different subtargets for each function, instprinter has to be changed to use the
per-function subtarget rather than the default subtarget.
This patch takes the first step towards enabling instprinter to change its
behavior based on the per-function subtarget. It adds a bit "PassSubtarget" to
AsmWriter which tells table-gen to pass a reference to MCSubtargetInfo to the
various print methods table-gen auto-generates.
I will follow up with changes to instprinters of AArch64, ARM, and X86.
llvm-svn: 233411
TargetMachine::getSubtargetImpl routines.
This keeps the target independent code free of bare subtarget
calls while the remainder of the backends are migrated, or not
if they don't wish to support per-function subtargets as would
be needed for function multiversioning or LTO of disparate
cpu subarchitecture types, e.g.
clang -msse4.2 -c foo.c -emit-llvm -o foo.bc
clang -c bar.c -emit-llvm -o bar.bc
llvm-link foo.bc bar.bc -o baz.bc
llc baz.bc
and get appropriate code for what the command lines requested.
llvm-svn: 232885
Summary:
This is instead of doing this in target independent code and is the last
non-functional change before targets begin to distinguish between
different memory constraints when selecting code for the ISD::INLINEASM
node.
Next, each target will individually move away from the idea that all
memory constraints behave like 'm'.
Subscribers: jholewinski, llvm-commits
Differential Revision: http://reviews.llvm.org/D8173
llvm-svn: 232373
The operand flag word for ISD::INLINEASM nodes now contains a 15-bit
memory constraint ID when the operand kind is Kind_Mem. This constraint
ID is a numeric equivalent to the constraint code string and is converted
with a target specific hook in TargetLowering.
This patch maps all memory constraints to InlineAsm::Constraint_m so there
is no functional change at this point. It just proves that using these
previously unused bits in the encoding of the flag word doesn't break
anything.
The next patch will make each target preserve the current mapping of
everything to Constraint_m for itself while changing the target independent
implementation of the hook to return Constraint_Unknown appropriately. Each
target will then be adapted in separate patches to use appropriate
Constraint_* values.
PR22883 was caused the matching operands copying the whole of the operand flags
for the matched operand. This included the constraint id which needed to be
replaced with the operand number. This has been fixed with a conversion
function. Following on from this, matching operands also used the operand
number as the constraint id. This has been fixed by looking up the matched
operand and taking it from there.
llvm-svn: 232165
This (r232027) has caused PR22883; so it seems those bits might be used by
something else after all. Reverting until we can figure out what else to do.
Original commit message:
The operand flag word for ISD::INLINEASM nodes now contains a 15-bit
memory constraint ID when the operand kind is Kind_Mem. This constraint
ID is a numeric equivalent to the constraint code string and is converted
with a target specific hook in TargetLowering.
This patch maps all memory constraints to InlineAsm::Constraint_m so there
is no functional change at this point. It just proves that using these
previously unused bits in the encoding of the flag word doesn't break anything.
The next patch will make each target preserve the current mapping of
everything to Constraint_m for itself while changing the target independent
implementation of the hook to return Constraint_Unknown appropriately. Each
target will then be adapted in separate patches to use appropriate Constraint_*
values.
llvm-svn: 232093
Summary:
The operand flag word for ISD::INLINEASM nodes now contains a 15-bit
memory constraint ID when the operand kind is Kind_Mem. This constraint
ID is a numeric equivalent to the constraint code string and is converted
with a target specific hook in TargetLowering.
This patch maps all memory constraints to InlineAsm::Constraint_m so there
is no functional change at this point. It just proves that using these
previously unused bits in the encoding of the flag word doesn't break anything.
The next patch will make each target preserve the current mapping of
everything to Constraint_m for itself while changing the target independent
implementation of the hook to return Constraint_Unknown appropriately. Each
target will then be adapted in separate patches to use appropriate Constraint_*
values.
Reviewers: hfinkel
Reviewed By: hfinkel
Subscribers: hfinkel, jholewinski, llvm-commits
Differential Revision: http://reviews.llvm.org/D8171
llvm-svn: 232027
Summary:
I don't know why every singled backend had to redeclare its own DataLayout.
There was a virtual getDataLayout() on the common base TargetMachine, the
default implementation returned nullptr. It was not clear from this that
we could assume at call site that a DataLayout will be available with
each Target.
Now getDataLayout() is no longer virtual and return a pointer to the
DataLayout member of the common base TargetMachine. I plan to turn it into
a reference in a future patch.
The only backend that didn't have a DataLayout previsouly was the CPPBackend.
It now initializes the default DataLayout. This commit is NFC for all the
other backends.
Test Plan: clang+llvm ninja check-all
Reviewers: echristo
Subscribers: jfb, jholewinski, llvm-commits
Differential Revision: http://reviews.llvm.org/D8243
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 231987
time. The target independent code was passing in one all the
time and targets weren't checking validity before using. Update
a few calls to pass in a MachineFunction where necessary.
llvm-svn: 231970
clang-cl would warn that this value is not representable in 'int':
enum { FeatureX = 1ULL << 31 };
All MS enums are 'ints' unless otherwise specified, so we have to use an
explicit type. The AMDGPU target just hit 32 features, triggering this
warning.
Now that we have C++11 strong enum types, we can also eliminate the
'const uint64_t' codepath from tablegen and just use 'enum : uint64_t'.
llvm-svn: 231697
a lookup, pass that in rather than use a naked call to getSubtargetImpl.
This involved passing down and around either a TargetMachine or
TargetRegisterInfo. Update all callers/definitions around the targets
and SelectionDAG.
llvm-svn: 230699
This required plumbing a TargetRegisterInfo through computeRegisterProperties
and into findRepresentativeClass which uses it for register class
iteration. This required passing a subtarget into a few target specific
initializations of TargetLowering.
llvm-svn: 230583
Everyone except R600 was manually passing the length of a static array
at each callsite, calculated in a variety of interesting ways. Far
easier to let ArrayRef handle that.
There should be no functional change, but out of tree targets may have
to tweak their calls as with these examples.
llvm-svn: 230118
LLVM's include tree and the use of using declarations to hide the
'legacy' namespace for the old pass manager.
This undoes the primary modules-hostile change I made to keep
out-of-tree targets building. I sent an email inquiring about whether
this would be reasonable to do at this phase and people seemed fine with
it, so making it a reality. This should allow us to start bootstrapping
with modules to a certain extent along with making it easier to mix and
match headers in general.
The updates to any code for users of LLVM are very mechanical. Switch
from including "llvm/PassManager.h" to "llvm/IR/LegacyPassManager.h".
Qualify the types which now produce compile errors with "legacy::". The
most common ones are "PassManager", "PassManagerBase", and
"FunctionPassManager".
llvm-svn: 229094
derived classes.
Since global data alignment, layout, and mangling is often based on the
DataLayout, move it to the TargetMachine. This ensures that global
data is going to be layed out and mangled consistently if the subtarget
changes on a per function basis. Prior to this all targets(*) have
had subtarget dependent code moved out and onto the TargetMachine.
*One target hasn't been migrated as part of this change: R600. The
R600 port has, as a subtarget feature, the size of pointers and
this affects global data layout. I've currently hacked in a FIXME
to enable progress, but the port needs to be updated to either pass
the 64-bitness to the TargetMachine, or fix the DataLayout to
avoid subtarget dependent features.
llvm-svn: 227113
utils/sort_includes.py.
I clearly haven't done this in a while, so more changed than usual. This
even uncovered a missing include from the InstrProf library that I've
added. No functionality changed here, just mechanical cleanup of the
include order.
llvm-svn: 225974
type (in addition to the memory type).
The *LoadExt* legalization handling used to only have one type, the
memory type. This forced users to assume that as long as the extload
for the memory type was declared legal, and the result type was legal,
the whole extload was legal.
However, this isn't always the case. For instance, on X86, with AVX,
this is legal:
v4i32 load, zext from v4i8
but this isn't:
v4i64 load, zext from v4i8
Whereas v4i64 is (arguably) legal, even without AVX2.
Note that the same thing was done a while ago for truncstores (r46140),
but I assume no one needed it yet for extloads, so here we go.
Calls to getLoadExtAction were changed to add the value type, found
manually in the surrounding code.
Calls to setLoadExtAction were mechanically changed, by wrapping the
call in a loop, to match previous behavior. The loop iterates over
the MVT subrange corresponding to the memory type (FP vectors, etc...).
I also pulled neighboring setTruncStoreActions into some of the loops;
those shouldn't make a difference, as the additional types are illegal.
(e.g., i128->i1 truncstores on PPC.)
No functional change intended.
Differential Revision: http://reviews.llvm.org/D6532
llvm-svn: 225421
Previously print+verify passes were added in a very unsystematic way, which is
annoying when debugging as you miss intermediate steps and allows bugs to stay
unnotice when no verification is performed.
To make this change practical I added the possibility to explicitely disable
verification. I used this option on all places where no verification was
performed previously (because alot of places actually don't pass the
MachineVerifier).
In the long term these problems should be fixed properly and verification
enabled after each pass. I'll enable some more verification in subsequent
commits.
This is the 2nd attempt at this after realizing that PassManager::add() may
actually delete the pass.
llvm-svn: 224059
Previously print+verify passes were added in a very unsystematic way, which is
annoying when debugging as you miss intermediate steps and allows bugs to stay
unnotice when no verification is performed.
To make this change practical I added the possibility to explicitely disable
verification. I used this option on all places where no verification was
performed previously (because alot of places actually don't pass the
MachineVerifier).
In the long term these problems should be fixed properly and verification
enabled after each pass. I'll enable some more verification in subsequent
commits.
llvm-svn: 224042
These recently all grew a unique_ptr<TargetLoweringObjectFile> member in
r221878. When anyone calls a virtual method of a class, clang-cl
requires all virtual methods to be semantically valid. This includes the
implicit virtual destructor, which triggers instantiation of the
unique_ptr destructor, which fails because the type being deleted is
incomplete.
This is just part of the ongoing saga of PR20337, which is affecting
Blink as well. Because the MSVC ABI doesn't have key functions, we end
up referencing the vtable and implicit destructor on any virtual call
through a class. We don't actually end up emitting the dtor, so it'd be
good if we could avoid this unneeded type completion work.
llvm-svn: 222480
Add header guards to files that were missing guards. Remove #endif comments
as they don't seem common in LLVM (we can easily add them back if we decide
they're useful)
Changes made by clang-tidy with minor tweaks.
llvm-svn: 215558
to get the subtarget and that's accessible from the MachineFunction
now. This helps clear the way for smaller changes where we getting
a subtarget will require passing in a MachineFunction/Function as
well.
llvm-svn: 214988
shorter/easier and have the DAG use that to do the same lookup. This
can be used in the future for TargetMachine based caching lookups from
the MachineFunction easily.
Update the MIPS subtarget switching machinery to update this pointer
at the same time it runs.
llvm-svn: 214838
Jim Grosbach