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[InstSimplify] simplifyUnsignedRangeCheck(): X >= Y && Y == 0 --> Y == 0 

https://rise4fun.com/Alive/v9Y4

llvm-svn: 372491
This commit is contained in:
Roman Lebedev 2019-09-21 22:27:39 +00:00
parent e94f156f77
commit baf809811b
2 changed files with 4 additions and 7 deletions
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7
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -1443,11 +1443,10 @@ static Value *simplifyUnsignedRangeCheck(ICmpInst *ZeroICmp,
isKnownNonZero(X, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
return IsAnd ? UnsignedICmp : ZeroICmp;
// X >= Y && Y == 0 --> Y == 0 FIXME
// X >= Y && Y == 0 --> Y == 0
// X >= Y || Y == 0 --> X >= Y
if (UnsignedPred == ICmpInst::ICMP_UGE && EqPred == ICmpInst::ICMP_EQ &&
!IsAnd)
return UnsignedICmp;
if (UnsignedPred == ICmpInst::ICMP_UGE && EqPred == ICmpInst::ICMP_EQ)
return IsAnd ? ZeroICmp : UnsignedICmp;
// X > Y && Y == 0 --> Y == 0 iff X != 0
// X > Y || Y == 0 --> X > Y iff X != 0

4
llvm/test/Transforms/InstSimplify/unsigned-range-checks.ll
View File

@ -84,9 +84,7 @@ define i1 @t7(i8 %x, i8 %y) {
define i1 @t8(i8 %x, i8 %y) {
; CHECK-LABEL: @t8(
; CHECK-NEXT: [[NOT_NULL:%.*]] = icmp eq i8 [[Y:%.*]], 0
; CHECK-NEXT: [[NO_UNDERFLOW:%.*]] = icmp ule i8 [[Y]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = and i1 [[NOT_NULL]], [[NO_UNDERFLOW]]
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 [[NOT_NULL]]
;
%not_null = icmp eq i8 %y, 0
%no_underflow = icmp ule i8 %y, %x