For remainder:
If (1 << (Bitwidth / 2)) % Divisor == 1, we can add the high and low halves
together and use a (Bitwidth / 2) urem. If (BitWidth /2) is a legal integer
type, this urem will be expand by DAGCombiner using multiply by magic
constant. We do have to take into account that adding high and low
together can produce a carry, making it a (BitWidth / 2)+1 bit number.
So we need to also add back in the carry from the first addition.
For division:
We can use the above trick to compute the remainder, subtract that
remainder from the dividend, then multiply by the multiplicative
inverse of the Divisor modulo (1 << BitWidth).
This is based on the section "Remainder by Summing Digits" in
Hacker's delight.
The remainder trick is similar to a trick you may have learned for
determining if a decimal number is divisible by 3. You can add all the
digits together and see if the sum is divisible by 3. If you're not sure
if the sum is divisible by 3, you can add its digits together. This
can be repeated until you have a single decimal digit. If that digit
is 3, 6, or 9, then the original number is divisible by 3. This works
because 10 % 3 == 1.
gcc already does this same trick. There are additional tricks gcc
does urem as well as srem, udiv, and sdiv that I plan to add in
future patches.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D130862
Also remove new-pass-manager version of ExpandLargeDivRem because there is no way
yet to access TargetLowering in the new pass manager.
Differential Revision: https://reviews.llvm.org/D133691
LLVM contains a helpful function for getting the size of a C-style
array: `llvm::array_lengthof`. This is useful prior to C++17, but not as
helpful for C++17 or later: `std::size` already has support for C-style
arrays.
Change call sites to use `std::size` instead.
Differential Revision: https://reviews.llvm.org/D133429
For now, clang and gcc both failed to generate sae version from _mm512_cvt_roundps_ph:
https://godbolt.org/z/oh7eTGY5z. Intrinsic guide description is also wrong, which will be
update soon.
Reviewed By: pengfei
Differential Revision: https://reviews.llvm.org/D132641
See if we can remove X86ISD::ANDNP nodes by checking the state of the knownbits of the demanded elements.
This is equivalent to the generic ISD::AND handling, but flips the bits of the LHS operand to account for ANDNP.
Differential Revision: https://reviews.llvm.org/D128216
The KCFI sanitizer, enabled with `-fsanitize=kcfi`, implements a
forward-edge control flow integrity scheme for indirect calls. It
uses a !kcfi_type metadata node to attach a type identifier for each
function and injects verification code before indirect calls.
Unlike the current CFI schemes implemented in LLVM, KCFI does not
require LTO, does not alter function references to point to a jump
table, and never breaks function address equality. KCFI is intended
to be used in low-level code, such as operating system kernels,
where the existing schemes can cause undue complications because
of the aforementioned properties. However, unlike the existing
schemes, KCFI is limited to validating only function pointers and is
not compatible with executable-only memory.
KCFI does not provide runtime support, but always traps when a
type mismatch is encountered. Users of the scheme are expected
to handle the trap. With `-fsanitize=kcfi`, Clang emits a `kcfi`
operand bundle to indirect calls, and LLVM lowers this to a
known architecture-specific sequence of instructions for each
callsite to make runtime patching easier for users who require this
functionality.
A KCFI type identifier is a 32-bit constant produced by taking the
lower half of xxHash64 from a C++ mangled typename. If a program
contains indirect calls to assembly functions, they must be
manually annotated with the expected type identifiers to prevent
errors. To make this easier, Clang generates a weak SHN_ABS
`__kcfi_typeid_<function>` symbol for each address-taken function
declaration, which can be used to annotate functions in assembly
as long as at least one C translation unit linked into the program
takes the function address. For example on AArch64, we might have
the following code:
```
.c:
int f(void);
int (*p)(void) = f;
p();
.s:
.4byte __kcfi_typeid_f
.global f
f:
...
```
Note that X86 uses a different preamble format for compatibility
with Linux kernel tooling. See the comments in
`X86AsmPrinter::emitKCFITypeId` for details.
As users of KCFI may need to locate trap locations for binary
validation and error handling, LLVM can additionally emit the
locations of traps to a `.kcfi_traps` section.
Similarly to other sanitizers, KCFI checking can be disabled for a
function with a `no_sanitize("kcfi")` function attribute.
Relands 67504c9549 with a fix for
32-bit builds.
Reviewed By: nickdesaulniers, kees, joaomoreira, MaskRay
Differential Revision: https://reviews.llvm.org/D119296
The KCFI sanitizer, enabled with `-fsanitize=kcfi`, implements a
forward-edge control flow integrity scheme for indirect calls. It
uses a !kcfi_type metadata node to attach a type identifier for each
function and injects verification code before indirect calls.
Unlike the current CFI schemes implemented in LLVM, KCFI does not
require LTO, does not alter function references to point to a jump
table, and never breaks function address equality. KCFI is intended
to be used in low-level code, such as operating system kernels,
where the existing schemes can cause undue complications because
of the aforementioned properties. However, unlike the existing
schemes, KCFI is limited to validating only function pointers and is
not compatible with executable-only memory.
KCFI does not provide runtime support, but always traps when a
type mismatch is encountered. Users of the scheme are expected
to handle the trap. With `-fsanitize=kcfi`, Clang emits a `kcfi`
operand bundle to indirect calls, and LLVM lowers this to a
known architecture-specific sequence of instructions for each
callsite to make runtime patching easier for users who require this
functionality.
A KCFI type identifier is a 32-bit constant produced by taking the
lower half of xxHash64 from a C++ mangled typename. If a program
contains indirect calls to assembly functions, they must be
manually annotated with the expected type identifiers to prevent
errors. To make this easier, Clang generates a weak SHN_ABS
`__kcfi_typeid_<function>` symbol for each address-taken function
declaration, which can be used to annotate functions in assembly
as long as at least one C translation unit linked into the program
takes the function address. For example on AArch64, we might have
the following code:
```
.c:
int f(void);
int (*p)(void) = f;
p();
.s:
.4byte __kcfi_typeid_f
.global f
f:
...
```
Note that X86 uses a different preamble format for compatibility
with Linux kernel tooling. See the comments in
`X86AsmPrinter::emitKCFITypeId` for details.
As users of KCFI may need to locate trap locations for binary
validation and error handling, LLVM can additionally emit the
locations of traps to a `.kcfi_traps` section.
Similarly to other sanitizers, KCFI checking can be disabled for a
function with a `no_sanitize("kcfi")` function attribute.
Reviewed By: nickdesaulniers, kees, joaomoreira, MaskRay
Differential Revision: https://reviews.llvm.org/D119296
This patch adds a Type operand to the TLI isCheapToSpeculateCttz/isCheapToSpeculateCtlz callbacks, allowing targets to decide whether branches should occur on a type-by-type/legality basis.
For X86, this patch proposes to allow CTTZ speculation for i8/i16 types that will lower to promoted i32 BSF instructions by masking the operand above the msb (we already do something similar for i8/i16 TZCNT). This required a minor tweak to CTTZ lowering - if the src operand is known never zero (i.e. due to the promotion masking) we can remove the CMOV zero src handling.
Although BSF isn't very fast, most CPUs from the last 20 years don't do that bad a job with it, although there are some annoying passthrough EFLAGS dependencies. Additionally, now that we emit 'REP BSF' in most cases, we are tending towards assuming this will most likely be executed as a TZCNT instruction on any semi-modern CPU.
Differential Revision: https://reviews.llvm.org/D132520
TragetLowering had two last InstructionCost related `getTypeLegalizationCost()`
and `getScalingFactorCost()` members, but all other costs are processed in TTI.
E.g. it is not comfortable to use other TTI members in these two functions
overrided in a target.
Minor refactoring: `getTypeLegalizationCost()` now doesn't need DataLayout
parameter - it was always passed from TTI.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D117723
There are two different senses in which a block can be "address-taken".
There can be a BlockAddress involved, which means we need to map the
IR-level value to some specific block of machine code. Or there can be
constructs inside a function which involve using the address of a basic
block to implement certain kinds of control flow.
Mixing these together causes a problem: if target-specific passes are
marking random blocks "address-taken", if we have a BlockAddress, we
can't actually tell which MachineBasicBlock corresponds to the
BlockAddress.
So split this into two separate bits: one for BlockAddress, and one for
the machine-specific bits.
Discovered while trying to sort out related stuff on D102817.
Differential Revision: https://reviews.llvm.org/D124697
Previously, LegaizeDAG didn't check mask.compress's passthrough might be float, and this lead to getConstant crash since it doesn't support fp
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D131947
I had hoped to make this a generic fold in DAGCombine, but there's quite a few regressions in Thumb2 MVE that need addressing first.
Fixes regressions from D106675.
This is to avoid f16->i64 being lowered to `__fixhfdi/__fixunshfdi` on 32-bits since neither libgcc nor compiler-rt provide them. https://godbolt.org/z/cjWEsea5v
It also helps to improve the performance by promoting the vector type.
Reviewed By: LuoYuanke
Differential Revision: https://reviews.llvm.org/D131828
lowerShuffleWithVPMOV currently only matches shuffle(truncate(x)) patterns, but on VLX targets the truncate isn't usually necessary to make the VPMOV node worthwhile (as we're only targetting v16i8/v8i16 shuffles we're almost always ending up with a PSHUFB node instead). PACKSS/PACKUS are still preferred vs VPMOV due to their lower uop count.
Fixes the remaining regression from the fixes in rG293899c64b75
This patch makes the variants of `mm*_cast*` intel intrinsics that use `shufflevector(freeze(poison), ..)` emit efficient assembly.
(These intrinsics are planned to use `shufflevector(freeze(poison), ..)` after shufflevector's semantics update; relevant thread: D103874)
To do so, this patch
1. Updates `LowerAVXCONCAT_VECTORS` in X86ISelLowering.cpp to recognize `FREEZE(UNDEF)` operand of `CONCAT_VECTOR` in addition to `UNDEF`
2. Updates X86InstrVecCompiler.td to recognize `insert_subvector` of `FREEZE(UNDEF)` vector as its first operand.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D130339
This adresses various regression in D131260 , as well as is a useful optimization in itself.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D131358
If we're going to emit a rep prefix before bsf as proposed in
D130956, it makes sense to promote i16 operations to i32 to avoid
the false depedency of tzcntw.
Reviewed By: skan, pengfei
Differential Revision: https://reviews.llvm.org/D130995
This patch ensures consistency in the construction of FP_ROUND nodes
such that they always use ISD::TargetConstant instead of ISD::Constant.
This additionally fixes a bug in the AArch64 SVE backend where patterns
were matching against TargetConstant nodes and sometimes failing when
passed a Constant node.
Reviewed By: paulwalker-arm
Differential Revision: https://reviews.llvm.org/D130370
The problem Alexander reported on D127982 was caused by an optimization
for AVX512-FP16 instruction. We must limit it to the feature enabled only.
During the investigation, I found we didn't expand for fp_round/fp_extend
without F16C. This may result runtime crash, so change them too.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D130817
Only PACKSS/PACKUS faux shuffles make use of the demanded elts at the moment, but this at least improves the handling of a couple of truncation patterns.
Noticed by inspection and I can't seem to make a test case, but SSE arithmetic bit shifts clamp to the max shift amount (i.e. create a sign splat) - combineVectorShiftImm already does something similar.
If the LHS op has a single use then using the more general AND op is likely to allow commutation, load folding, generic folds etc.
Updated version - original version rG057db2002bb3 didn't correctly account for multiple uses of the mask that might be folding "OR(AND(X,C),AND(Y,~C)) -> OR(AND(X,C),ANDNP(C,Y))" in canonicalizeBitSelect
Currently the X86 shuffle lowering would widen the element type for
shuffle if the mask element value is adjacent. For below example
%t2 = add nsw <16 x i32> %t0, %t1
%t3 = sub nsw <16 x i32> %t0, %t1
%t4 = shufflevector <16 x i32> %t2, <16 x i32> %t3,
<16 x i32> <i32 16, i32 17, i32 2, i32 3, i32 4,
i32 5, i32 6, i32 7, i32 8, i32 9, i32 10,
i32 11, i32 12, i32 13, i32 14, i32 15>
ret <16 x i32> %t4
Compiler would transform the shuffle to
%t4 = shufflevector <8 x i64> %t2, <8 x i64> %t3,
<8 x i64> <i32 8, i32 1, i32 2, i32 3, i32 4,
i32 5, i32 6, i32 7>
This may lose the oppotunity to let ISel select mask instruction when
avx512 is enabled.
This patch is to prevent the tranform when avx512 feature is enabled.
Thank Simon for the idea.
Differential Revision: https://reviews.llvm.org/D129537
With SSE4.1 and above we were using 3 multiply instructions. This
was due to type legalization widening to v4i32 and the low half
being done with pmulld while the high half used two pmuldq/pmuludq.
Instead of that, we can use a single pmuludq/pmuldq to calculate
the full product at once, extract the high and low bits and compare
to check for overflow.
I've restricted SMULO to sse4.1 to get pmuldq. We can probably
do a fixup to pmuludq on earlier targets, but that's for another day.
I was going through my git stash and found an early version of this patch
from a year or two ago so I went ahead and finished it.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D130432
For mask ops like these, the other operand's corresponding element might be zero (result = zero) - so we must demand all the bits and that element.
This appears to be what D128570 was trying to fix - both sides of the funnel shift mask of the vXi64 (legalized to v2Xi32) were incorrectly simplifying the upper 32-bit halves to undef, resulting in bad folds later on.
I intend to address the test case regressions, but this close to the release branch I'd prefer to get a fix in first.
Minor bit of prep work toward not unnecessarily widening shuffle operands in combineX86ShufflesRecursively, instead only widening in combineX86ShuffleChain if we actual find a match - see Issue #45319
An async suspend models the split between two partial async functions.
`llvm.swift.async.context.addr ` will have a different value in the two
partial functions so it is not correct to generally CSE the instruction.
rdar://97336162
Differential Revision: https://reviews.llvm.org/D130201
Craig Topper