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[InstCombine] foldUnsignedUnderflowCheck(): one last pattern with 'sub' (PR43251) 

https://rise4fun.com/Alive/0j9

llvm-svn: 372930
This commit is contained in:
Roman Lebedev 2019-09-25 22:59:59 +00:00
parent ca524621d1
commit a2fa03af3a
2 changed files with 14 additions and 8 deletions
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10
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1128,6 +1128,16 @@ static Value *foldUnsignedUnderflowCheck(ICmpInst *ZeroICmp,
EqPred == ICmpInst::ICMP_EQ && !IsAnd)
return Builder.CreateICmpULE(Base, Offset);
// Base <= Offset && (Base - Offset) != 0 --> Base < Offset
if (UnsignedPred == ICmpInst::ICMP_ULE && EqPred == ICmpInst::ICMP_NE &&
IsAnd)
return Builder.CreateICmpULT(Base, Offset);
// Base > Offset || (Base - Offset) == 0 --> Base >= Offset
if (UnsignedPred == ICmpInst::ICMP_UGT && EqPred == ICmpInst::ICMP_EQ &&
!IsAnd)
return Builder.CreateICmpUGE(Base, Offset);
return nullptr;
}

12
llvm/test/Transforms/InstCombine/result-of-usub-is-non-zero-and-no-overflow.ll
View File

@ -404,10 +404,8 @@ define i1 @base_ult_offset(i8 %base, i8 %offset) {
; CHECK-LABEL: @base_ult_offset(
; CHECK-NEXT: [[ADJUSTED:%.*]] = sub i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[NOT_NULL:%.*]] = icmp ne i8 [[ADJUSTED]], 0
; CHECK-NEXT: [[NO_UNDERFLOW:%.*]] = icmp ule i8 [[BASE]], [[OFFSET]]
; CHECK-NEXT: [[R:%.*]] = and i1 [[NO_UNDERFLOW]], [[NOT_NULL]]
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i8 [[BASE]], [[OFFSET]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%adjusted = sub i8 %base, %offset
call void @use8(i8 %adjusted)
@ -420,10 +418,8 @@ define i1 @base_uge_offset(i8 %base, i8 %offset) {
; CHECK-LABEL: @base_uge_offset(
; CHECK-NEXT: [[ADJUSTED:%.*]] = sub i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[NOT_NULL:%.*]] = icmp eq i8 [[ADJUSTED]], 0
; CHECK-NEXT: [[NO_UNDERFLOW:%.*]] = icmp ugt i8 [[BASE]], [[OFFSET]]
; CHECK-NEXT: [[R:%.*]] = or i1 [[NO_UNDERFLOW]], [[NOT_NULL]]
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp uge i8 [[BASE]], [[OFFSET]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%adjusted = sub i8 %base, %offset
call void @use8(i8 %adjusted)