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[InstCombine] add use check to shl transform 

This bug was introduced with the refactoring in:
9075edc89b
...but there were no tests to detect it.
This commit is contained in:
Sanjay Patel 2021-09-27 13:49:13 -04:00
parent d992950078
commit 623f93ed1c
2 changed files with 3 additions and 5 deletions
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2
llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
View File

@ -860,7 +860,7 @@ Instruction *InstCombinerImpl::visitShl(BinaryOperator &I) {
// we have confidence that the shifts will get folded together.
Instruction *TrOp;
const APInt *TrShiftAmt;
if (match(Op0, m_Trunc(m_Instruction(TrOp))) &&
if (match(Op0, m_OneUse(m_Trunc(m_Instruction(TrOp)))) &&
match(TrOp, m_OneUse(m_Shift(m_Value(), m_APInt(TrShiftAmt)))) &&
TrShiftAmt->ult(TrOp->getType()->getScalarSizeInBits())) {
Type *SrcTy = TrOp->getType();

6
llvm/test/Transforms/InstCombine/shift-shift.ll
View File

@ -198,8 +198,7 @@ define i8 @shl_trunc_bigger_lshr_use2(i32 %x) {
; CHECK-NEXT: [[RT:%.*]] = lshr i32 [[X:%.*]], 5
; CHECK-NEXT: [[TR:%.*]] = trunc i32 [[RT]] to i8
; CHECK-NEXT: call void @use8(i8 [[TR]])
; CHECK-NEXT: [[LT1:%.*]] = shl nuw nsw i32 [[RT]], 3
; CHECK-NEXT: [[LT:%.*]] = trunc i32 [[LT1]] to i8
; CHECK-NEXT: [[LT:%.*]] = shl i8 [[TR]], 3
; CHECK-NEXT: ret i8 [[LT]]
;
%rt = lshr i32 %x, 5
@ -214,8 +213,7 @@ define i8 @shl_trunc_smaller_lshr_use2(i32 %x) {
; CHECK-NEXT: [[RT:%.*]] = lshr i32 [[X:%.*]], 3
; CHECK-NEXT: [[TR:%.*]] = trunc i32 [[RT]] to i8
; CHECK-NEXT: call void @use8(i8 [[TR]])
; CHECK-NEXT: [[LT1:%.*]] = shl i32 [[RT]], 5
; CHECK-NEXT: [[LT:%.*]] = trunc i32 [[LT1]] to i8
; CHECK-NEXT: [[LT:%.*]] = shl i8 [[TR]], 5
; CHECK-NEXT: ret i8 [[LT]]
;
%rt = lshr i32 %x, 3