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[ValueTracking] Handle shufflevector constants in ComputeNumSignBits

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Differential Revision: https://reviews.llvm.org/D78688
This commit is contained in:
Eli Friedman 2020-04-22 17:15:39 -07:00
parent 68392a914f
commit 9ef37e59d4
2 changed files with 17 additions and 1 deletions
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6
lib/Analysis/ValueTracking.cpp
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@ -2906,7 +2906,11 @@ static unsigned ComputeNumSignBitsImpl(const Value *V,
case Instruction::ShuffleVector: {
// Collect the minimum number of sign bits that are shared by every vector
// element referenced by the shuffle.
auto *Shuf = cast<ShuffleVectorInst>(U);
auto *Shuf = dyn_cast<ShuffleVectorInst>(U);
if (!Shuf) {
// FIXME: Add support for shufflevector constant expressions.
return 1;
}
APInt DemandedLHS, DemandedRHS;
// For undef elements, we don't know anything about the common state of
// the shuffle result.

12
test/Transforms/InstCombine/nsw.ll
View File

@ -128,3 +128,15 @@ define <3 x i32> @shl_nuw_nsw_shuffle_undef_elt_splat_vec(<2 x i8> %x) {
ret <3 x i32> %t3
}
; Make sure we don't crash on a ConstantExpr shufflevector
define <vscale x 2 x i64> @mul_nuw_nsw_shuffle_constant_expr(<vscale x 2 x i8> %z) {
; CHECK-LABEL: @mul_nuw_nsw_shuffle_constant_expr(
; CHECK-NEXT: [[XX:%.*]] = zext <vscale x 2 x i8> [[Z:%.*]] to <vscale x 2 x i64>
; CHECK-NEXT: [[T3:%.*]] = mul <vscale x 2 x i64> [[XX]], shufflevector (<vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 3, i32 0), <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i32> zeroinitializer)
; CHECK-NEXT: ret <vscale x 2 x i64> [[T3]]
;
%xx = zext <vscale x 2 x i8> %z to <vscale x 2 x i64>
%shuf = shufflevector <vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 3, i32 0), <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i32> zeroinitializer
%t3 = mul <vscale x 2 x i64> %shuf, %xx
ret <vscale x 2 x i64> %t3
}