This DAG combine was incorrect for big-endian targets, because it
assumes that when a bitcast changes the lane width, the
least-significant bits of the wider lanes are in the lower-numbered
lanes of the smaller type, which is only true for little-endian.
For IR like this:
%icmp = icmp ult <4 x i32> %a, splat (i32 5)
%res = extractelement <4 x i1> %icmp, i32 1
where there is only one use of %icmp we can take a similar approach
to what we already do for binary ops such add, sub, etc. and convert
this into
%ext = extractelement <4 x i32> %a, i32 1
%res = icmp ult i32 %ext, 5
For AArch64 targets at least the scalar boolean result will almost
certainly need to be in a GPR anyway, since it will probably be
used by branches for control flow. I've tried to reuse existing code
in scalarizeExtractedBinop to also work for setcc.
NOTE: The optimisations don't apply for tests such as
extract_icmp_v4i32_splat_rhs in the file
CodeGen/AArch64/extract-vector-cmp.ll
because scalarizeExtractedBinOp only works if one of the input
operands is a constant.
When extracting a smaller integer from a scalar_to_vector source, we were limited to only folding/truncating the lowest bits of the scalar source.
This patch extends the fold to handle extraction of any other element, by right shifting the source before truncation.
Fixes a regression from #117884
For IR like this:
%icmp = icmp ult <4 x i32> %a, splat (i32 5)
%res = extractelement <4 x i1> %icmp, i32 1
where there is only one use of %icmp we can take a similar approach
to what we already do for binary ops such add, sub, etc. and convert
this into
%ext = extractelement <4 x i32> %a, i32 1
%res = icmp ult i32 %ext, 5
For AArch64 targets at least the scalar boolean result will almost
certainly need to be in a GPR anyway, since it will probably be
used by branches for control flow. I've tried to reuse existing code
in scalarizeExtractedBinop to also work for setcc.
NOTE: The optimisations don't apply for tests such as
extract_icmp_v4i32_splat_rhs in the file
CodeGen/AArch64/extract-vector-cmp.ll
because scalarizeExtractedBinOp only works if one of the input
operands is a constant.
Currently the function will walk the entire DAG to find other candidates
to perform a post-inc store. This leads to very long compilation times
on large functions. Added a MaxSteps limit to avoid this, which is also
aligned to how hasPredecessorHelper is used elsewhere in the code.
For some reason there was a hasOneUse check on the splat for the
second operand and it's not obvious to me why. The check blocks
optimisations for lowering of nodes like AVGFLOORU and AVGCEILU.
In a follow-on patch I also plan to improve the generated code
for AVGCEILU further by teaching computeKnownBits about
zero-extending masked loads.
If we're masking the LSB of a SRL node result and that is shifting down an extended sign bit, see if we can change the SRL to shift down the MSB directly.
These patterns can occur during legalisation when we've sign extended to a wider type but the SRL is still shifting from the subreg.
Alternative to #114967
Fixes the remaining regression in #112588
This teaches dagcombiner to fold:
`(asr (add nsw x, y), 1) -> (avgfloors x, y)`
`(lsr (add nuw x, y), 1) -> (avgflooru x, y)`
as well the combine them to a ceil variant:
`(avgfloors (add nsw x, y), 1) -> (avgceils x, y)`
`(avgflooru (add nuw x, y), 1) -> (avgceilu x, y)`
iff valid for the target.
Removes some of the ARM MVE patterns that are now dead code.
It adds the avg opcodes to `IsQRMVEInstruction` as to preserve the
immediate splatting as before.
On ANDNOT capable targets we can always do this profitably, without ANDNOT we only attempt this if we don't introduce an additional NOT
Followup to #112547
Alter both isConstantIntBuildVectorOrConstantInt + isConstantFPBuildVectorOrConstantFP to return a bool instead of the underlying SDNode, and adjust usage to account for this.
Update isConstantIntBuildVectorOrConstantInt to peek though bitcasts when attempting to find a constant, in particular this improves canonicalization of constants to the RHS on commutable instructions.
X86 is the beneficiary here as it often bitcasts rematerializable 0/-1 vector constants as vXi32 and bitcasts to the requested type
Minor cleanup that helps with #107423
Reapplied after regression fix ba1255def64a9c3c68d97ace051eec76f546eeb0
Noticed while triaging the regression from #112710 noticed by @mstorsjo - don't rely on isConstantIntBuildVectorOrConstantInt+getNode to guarantee constant folding (if it fails to constant fold it will infinite loop), use FoldConstantArithmetic instead.
Alter both isConstantIntBuildVectorOrConstantInt + isConstantFPBuildVectorOrConstantFP to return a bool instead of the underlying SDNode, and adjust usage to account for this.
Update isConstantIntBuildVectorOrConstantInt to peek though bitcasts when attempting to find a constant, in particular this improves canonicalization of constants to the RHS on commutable instructions.
X86 is the beneficiary here as it often bitcasts rematerializable 0/-1 vector constants as vXi32 and bitcasts to the requested type
Minor cleanup that helps with #107423
Don't rely on isConstantFPBuildVectorOrConstantFP followed by getNode() will constant fold - FoldConstantArithmetic will do all of this for us.
Cleanup for #112682
Don't rely on isConstantFPBuildVectorOrConstantFP followed by getNode() will constant fold - FoldConstantArithmetic will do all of this for us.
Cleanup for #112682
Don't rely on isConstantFPBuildVectorOrConstantFP followed by getNode() will constant fold - FoldConstantArithmetic will do all of this for us.
Cleanup for #112682
Don't rely on isConstantIntBuildVectorOrConstantInt followed by getNode() will constant fold - FoldConstantArithmetic will do all of this for us.
Cleanup for #112682
Fix a check for extending loads in DAGCombiner,
where if the result type has more bits than the
loaded type it should count as an extending load.
All backends apart from AArch64 ignore this
ExtTy argument to shouldReduceLoadWidth, so this
change currently only impacts AArch64.
This patch adds icmp+select patterns for integer min/max matchers in
SDPatternMatch, similar to those in IR PatternMatch.
Reapply #111774.
Closes#108218.
This DAG combine replaces a floating-point load/store pair which has no
other uses with an integer one, but did not copy the memory operand
flags to the new instructions, resulting in it dropping the volatile
flag. This optimisation is still valid if one or both of the
instructions is volatile, so we can copy over the whole
MachineMemOperand to generate volatile integer loads and stores where
needed.
This PR is related to #99591. In this PR, instead of modifying how the
legalisation occurs depending on surrounding instructions, we refine
after legalisation.
This PR has two parts:
* `SDPatternMatch/MatchContext`: Modify a little bit the code to match
Operands (used by `m_Node(...)`) and Unary/Binary/Ternary Patterns to
make it compatible with `VPMatchContext`, instead of only `m_Opc`
supported. Some tests were added to ensure no regressions.
* `DAGCombiner`: Add a `foldSubCtlzNot` which detect and rewrite the
patterns using matching context.
Remaining Tasks:
- [ ] GlobalISel
- [ ] Currently the pattern matching will occur even before
legalisation. Should I restrict it to specific stages instead ?
- [ ] Style: Add a visitVP_SUB ?? Move `foldSubCtlzNot` in another
location for style consistency purpose ?
@topperc
---------
Co-authored-by: v01dxyz <v01dxyz@v01d.xyz>
