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clang-p2996/llvm/test/Transforms/InstCombine
Luke Lau 9a5b0f302b Reapply "[InstCombine] Match scalable splats in m_ImmConstant (#132522)" (#134262)
This reapplies #132522.

Previously casts of scalable m_ImmConstant splats weren't being folded
by ConstantFoldCastOperand, triggering the "Constant-fold of ImmConstant
should not fail" assertion.

There are no changes to the code in this PR, instead we just needed
#133207 to land first.

A test has been added for the assertion in
llvm/test/Transforms/InstSimplify/vec-icmp-of-cast.ll
@icmp_ult_sext_scalable_splat_is_true.

<hr/>

#118806 fixed an infinite loop in FoldShiftByConstant that could occur
when the shift amount was a ConstantExpr.

However this meant that FoldShiftByConstant no longer kicked in for
scalable vectors because scalable splats are represented by
ConstantExprs.

This fixes it by allowing scalable splats of non-ConstantExprs in
m_ImmConstant, which also fixes a few other test cases where scalable
splats were being missed.

But I'm also hoping that UseConstantIntForScalableSplat will eventually
remove the need for this.

I noticed this when trying to reverse a combine on RISC-V in #132245,
and saw that the resulting vector and scalar forms were different.
2025-04-03 18:03:16 +01:00
..

This directory contains test cases for the instcombine transformation.  The
dated tests are actual bug tests, whereas the named tests are used to test
for features that the this pass should be capable of performing.