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[InstCombine] convert mul with sexted bool and constant to select 

We already have the related folds for zext-of-bool, so it
should make things more consistent to have this transform
to select for sext-of-bool too:
https://alive2.llvm.org/ce/z/YikdfA

Fixes #53319
This commit is contained in:
Sanjay Patel 2022-01-20 14:51:45 -05:00
parent 4c1dc65015
commit a7a2860d0e
2 changed files with 13 additions and 7 deletions
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12
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -348,13 +348,21 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
return CastInst::Create(Instruction::SExt, And, I.getType());
}
// (bool X) * Y --> X ? Y : 0
// Y * (bool X) --> X ? Y : 0
// (zext bool X) * Y --> X ? Y : 0
// Y * (zext bool X) --> X ? Y : 0
if (match(Op0, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1))
return SelectInst::Create(X, Op1, ConstantInt::get(I.getType(), 0));
if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1))
return SelectInst::Create(X, Op0, ConstantInt::get(I.getType(), 0));
// (sext bool X) * C --> X ? -C : 0
Constant *ImmC;
if (match(Op0, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1) &&
match(Op1, m_ImmConstant(ImmC))) {
Constant *NegC = ConstantExpr::getNeg(ImmC);
return SelectInst::Create(X, NegC, ConstantInt::getNullValue(I.getType()));
}
// (lshr X, 31) * Y --> (ashr X, 31) & Y
// Y * (lshr X, 31) --> (ashr X, 31) & Y
// TODO: We are not checking one-use because the elimination of the multiply

8
llvm/test/Transforms/InstCombine/mul.ll
View File

@ -133,8 +133,7 @@ define <2 x i32> @mul_bool_vec_commute(<2 x i32> %px, <2 x i1> %y) {
define i32 @mul_sext_bool(i1 %x) {
; CHECK-LABEL: @mul_sext_bool(
; CHECK-NEXT: [[S:%.*]] = sext i1 [[X:%.*]] to i32
; CHECK-NEXT: [[M:%.*]] = mul nsw i32 [[S]], 42
; CHECK-NEXT: [[M:%.*]] = select i1 [[X:%.*]], i32 -42, i32 0
; CHECK-NEXT: ret i32 [[M]]
;
%s = sext i1 %x to i32
@ -146,7 +145,7 @@ define i32 @mul_sext_bool_use(i1 %x) {
; CHECK-LABEL: @mul_sext_bool_use(
; CHECK-NEXT: [[S:%.*]] = sext i1 [[X:%.*]] to i32
; CHECK-NEXT: call void @use32(i32 [[S]])
; CHECK-NEXT: [[M:%.*]] = mul nsw i32 [[S]], 42
; CHECK-NEXT: [[M:%.*]] = select i1 [[X]], i32 -42, i32 0
; CHECK-NEXT: ret i32 [[M]]
;
%s = sext i1 %x to i32
@ -157,8 +156,7 @@ define i32 @mul_sext_bool_use(i1 %x) {
define <2 x i8> @mul_sext_bool_vec(<2 x i1> %x) {
; CHECK-LABEL: @mul_sext_bool_vec(
; CHECK-NEXT: [[S:%.*]] = sext <2 x i1> [[X:%.*]] to <2 x i8>
; CHECK-NEXT: [[M:%.*]] = mul <2 x i8> [[S]], <i8 42, i8 -128>
; CHECK-NEXT: [[M:%.*]] = select <2 x i1> [[X:%.*]], <2 x i8> <i8 -42, i8 -128>, <2 x i8> zeroinitializer
; CHECK-NEXT: ret <2 x i8> [[M]]
;
%s = sext <2 x i1> %x to <2 x i8>