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[SCEV] accurate range for addrecexpr with nuw flag

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If addrecexpr has nuw flag, the value should never be less than its
start value and start value does not required to be SCEVConstant.

Reviewed By: nikic, sanjoy

Differential Revision: https://reviews.llvm.org/D71690
This commit is contained in:
Zheng Chen 2020-01-12 20:22:37 -05:00
parent 9ea03cb0fe
commit d8d9e920a8
2 changed files with 8 additions and 7 deletions
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11
lib/Analysis/ScalarEvolution.cpp
View File

@ -5672,11 +5672,12 @@ ScalarEvolution::getRangeRef(const SCEV *S,
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
// If there's no unsigned wrap, the value will never be less than its
// initial value.
if (AddRec->hasNoUnsignedWrap())
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
if (!C->getValue()->isZero())
ConservativeResult = ConservativeResult.intersectWith(
ConstantRange(C->getAPInt(), APInt(BitWidth, 0)), RangeType);
if (AddRec->hasNoUnsignedWrap()) {
APInt UnsignedMinValue = getUnsignedRangeMin(AddRec->getStart());
if (!UnsignedMinValue.isNullValue())
ConservativeResult = ConservativeResult.intersectWith(
ConstantRange(UnsignedMinValue, APInt(BitWidth, 0)), RangeType);
}
// If there's no signed wrap, and all the operands except initial value have
// the same sign or zero, the value won't ever be:

4
test/Analysis/ScalarEvolution/range_nw_flag.ll
View File

@ -2,7 +2,7 @@
; copied from flags-from-poison.ll
; CHECK-LABEL: @test-add-nuw
; CHECK: --> {(1 + %offset)<nuw>,+,1}<nuw><%loop> U: full-set S: full-set
; CHECK: --> {(1 + %offset)<nuw>,+,1}<nuw><%loop> U: [1,0) S: [1,0)
define void @test-add-nuw(float* %input, i32 %offset, i32 %numIterations) {
entry:
br label %loop
@ -20,7 +20,7 @@ exit:
}
; CHECK-LABEL: @test-addrec-nuw
; CHECK: --> {(1 + (10 smax %offset))<nuw>,+,1}<nuw><%loop> U: full-set S: full-set
; CHECK: --> {(1 + (10 smax %offset))<nuw>,+,1}<nuw><%loop> U: [11,0) S: [11,0)
define void @test-addrec-nuw(float* %input, i32 %offset, i32 %numIterations) {
entry:
%cmp = icmp sgt i32 %offset, 10