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[InstCombine] remove unnecessary one-use check from (C2 << X) << C1 fold 

The restriction goes back to:
16f18ed7b5
...but the fold only replaces a shift with a shift, so that's not necessary.
Generalizing to other opcodes is planned as a follow-up.
This commit is contained in:
Sanjay Patel 2022-05-30 15:15:27 -04:00
parent a004438959
commit c5d942a4fb
2 changed files with 2 additions and 2 deletions
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2
llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
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@ -1010,7 +1010,7 @@ Instruction *InstCombinerImpl::visitShl(BinaryOperator &I) {
Constant *C2;
Value *X;
// (C2 << X) << C1 --> (C2 << C1) << X
if (match(Op0, m_OneUse(m_Shl(m_Constant(C2), m_Value(X)))))
if (match(Op0, m_Shl(m_Constant(C2), m_Value(X))))
return BinaryOperator::CreateShl(ConstantExpr::getShl(C2, C1), X);
// (X * C2) << C1 --> X * (C2 << C1)

2
llvm/test/Transforms/InstCombine/shift-shift.ll
View File

@ -325,7 +325,7 @@ define i32 @shl_shl_constants_use(i32 %x) {
; CHECK-LABEL: @shl_shl_constants_use(
; CHECK-NEXT: [[S:%.*]] = shl i32 -2013265920, [[X:%.*]]
; CHECK-NEXT: call void @use32(i32 [[S]])
; CHECK-NEXT: [[R:%.*]] = shl i32 [[S]], 3
; CHECK-NEXT: [[R:%.*]] = shl i32 1073741824, [[X]]
; CHECK-NEXT: ret i32 [[R]]
;
%s = shl i32 2281701376, %x ; 0x8800_0000