For a long time, the InstCombine pass handled target specific
intrinsics. Having target specific code in general passes was noted as
an area for improvement for a long time.
D81728 moves most target specific code out of the InstCombine pass.
Applying the target specific combinations in an extra pass would
probably result in inferior optimizations compared to the current
fixed-point iteration, therefore the InstCombine pass resorts to newly
introduced functions in the TargetTransformInfo when it encounters
unknown intrinsics.
The patch should not have any effect on generated code (under the
assumption that code never uses intrinsics from a foreign target).
This introduces three new functions:
TargetTransformInfo::instCombineIntrinsic
TargetTransformInfo::simplifyDemandedUseBitsIntrinsic
TargetTransformInfo::simplifyDemandedVectorEltsIntrinsic
A few target specific parts are left in the InstCombine folder, where
it makes sense to share code. The largest left-over part in
InstCombineCalls.cpp is the code shared between arm and aarch64.
This allows to move about 3000 lines out from InstCombine to the targets.
Differential Revision: https://reviews.llvm.org/D81728
And simultaneously enhance SimplifyDemandedVectorElts() to rcognize that
pattern. That preserves some of the old optimizations in IR.
Given a shuffle that includes undef elements in an otherwise identity mask like:
define <4 x float> @shuffle(<4 x float> %arg) {
%shuf = shufflevector <4 x float> %arg, <4 x float> undef, <4 x i32> <i32 undef, i32 1, i32 2, i32 3>
ret <4 x float> %shuf
}
We were simplifying that to the input operand.
But as discussed in PR43958:
https://bugs.llvm.org/show_bug.cgi?id=43958
...that means that per-vector-element poison that would be stopped by the shuffle can now
leak to the result.
Also note that we still have (and there are tests for) the same transform with no undef
elements in the mask (a fully-defined identity mask). I don't think there's any
controversy about that case - it's a valid transform under any interpretation of
shufflevector/undef/poison.
Looking at a few of the diffs into codegen, I don't see any difference in final asm. So
depending on your perspective, that's good (no real loss of optimization power) or bad
(poison exists in the DAG, so we only partially fixed the bug).
Differential Revision: https://reviews.llvm.org/D70246
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
Tests with target intrinsics are inherently target specific, so it
doesn't actually make sense to run them if we've excluded their
target.
llvm-svn: 302979
Sebastian Neubauer