[PATCH] D71690: [SCEV] get a more accurate range for AddRecExpr with nuw flag
ChenZheng via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sun Dec 29 19:41:28 PST 2019
shchenz updated this revision to Diff 235532.
shchenz added a comment.
for signed range with `nsw` flag, we can only use the sign min value when constant range for START can not cross 0.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D71690/new/
https://reviews.llvm.org/D71690
Files:
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/test/Analysis/ScalarEvolution/range_nw_flag.ll
Index: llvm/test/Analysis/ScalarEvolution/range_nw_flag.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/range_nw_flag.ll
+++ llvm/test/Analysis/ScalarEvolution/range_nw_flag.ll
@@ -20,7 +20,7 @@
}
; 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: full-set
define void @test-addrec-nuw(float* %input, i32 %offset, i32 %numIterations) {
entry:
%cmp = icmp sgt i32 %offset, 10
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -5654,11 +5654,17 @@
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 MinValue = APInt(BitWidth, 0);
+ const SCEV *Start = AddRec->getStart();
+ if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED)
+ MinValue = getUnsignedRangeMin(AddRec->getStart());
+ else if (isKnownNonNegative(Start) || isKnownNonPositive(Start))
+ MinValue = getSignedRangeMin(Start);
+ if (!MinValue.isNullValue())
+ ConservativeResult = ConservativeResult.intersectWith(
+ ConstantRange(MinValue, APInt(BitWidth, 0)), RangeType);
+ }
// If there's no signed wrap, and all the operands have the same sign or
// zero, the value won't ever change sign.
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