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[InstCombine] Drop UB-implying attrs/metadata after speculating an instruction #85542

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Merged
merged 2 commits into from
Mar 17, 2024
Merged

[InstCombine] Drop UB-implying attrs/metadata after speculating an instruction #85542

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13788ab
[InstCombine] Add pre-commit tests for PR85536. NFC.
dtcxzyw Mar 16, 2024
caf2a3b
[InstCombine] Drop ub-implying attrs and metadata after speculating a…
dtcxzyw Mar 16, 2024
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1 change: 1 addition & 0 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1650,6 +1650,7 @@ static Value *foldOperationIntoSelectOperand(Instruction &I, SelectInst *SI,
Value *NewOp, InstCombiner &IC) {
Instruction *Clone = I.clone();
Clone->replaceUsesOfWith(SI, NewOp);
Clone->dropUBImplyingAttrsAndMetadata();
IC.InsertNewInstBefore(Clone, SI->getIterator());
return Clone;
}
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40 changes: 40 additions & 0 deletions llvm/test/Transforms/InstCombine/intrinsic-select.ll
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Expand Up @@ -240,3 +240,43 @@ define i32 @vec_to_scalar_select_vector(<2 x i1> %b) {
%c = call i32 @llvm.vector.reduce.add.v2i32(<2 x i32> %s)
ret i32 %c
}

define i8 @test_drop_noundef(i1 %cond, i8 %val) {
; CHECK-LABEL: @test_drop_noundef(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = call i8 @llvm.smin.i8(i8 [[VAL:%.*]], i8 0)
; CHECK-NEXT: [[RET:%.*]] = select i1 [[COND:%.*]], i8 -1, i8 [[TMP0]]
; CHECK-NEXT: ret i8 [[RET]]
;
entry:
%sel = select i1 %cond, i8 -1, i8 %val
%ret = call noundef i8 @llvm.smin.i8(i8 %sel, i8 0)
ret i8 %ret
}

define i1 @pr85536(i32 %a) {
; CHECK-LABEL: @pr85536(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i32 [[A:%.*]], 31
; CHECK-NEXT: [[SHL1:%.*]] = shl nsw i32 -1, [[A]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[SHL1]] to i64
; CHECK-NEXT: [[SHL2:%.*]] = shl i64 [[ZEXT]], 48
; CHECK-NEXT: [[SHR:%.*]] = ashr exact i64 [[SHL2]], 48
; CHECK-NEXT: [[TMP0:%.*]] = call i64 @llvm.smin.i64(i64 [[SHR]], i64 0)
; CHECK-NEXT: [[TMP1:%.*]] = and i64 [[TMP0]], 65535
; CHECK-NEXT: [[RET1:%.*]] = icmp eq i64 [[TMP1]], 0
; CHECK-NEXT: [[RET:%.*]] = select i1 [[CMP1]], i1 [[RET1]], i1 false
; CHECK-NEXT: ret i1 [[RET]]
;
entry:
%cmp1 = icmp ugt i32 %a, 30
%shl1 = shl nsw i32 -1, %a
%zext = zext i32 %shl1 to i64
%shl2 = shl i64 %zext, 48
%shr = ashr exact i64 %shl2, 48
%sel = select i1 %cmp1, i64 -1, i64 %shr
%smin = call noundef i64 @llvm.smin.i64(i64 %sel, i64 0)
%masked = and i64 %smin, 65535
%ret = icmp eq i64 %masked, 0
ret i1 %ret
}
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