[llvm] c6073d7 - [LoopCacheAnalysis] Drop incorrect nowrap flags from addrec (#164796)

[via llvm-commits]

Author: Ryotaro Kasuga
Date: 2025-10-24T00:32:34+09:00
New Revision: c6073d72ee23d8cd6aa49c08edde846359e41bde

URL: https://github.com/llvm/llvm-project/commit/c6073d72ee23d8cd6aa49c08edde846359e41bde
DIFF: https://github.com/llvm/llvm-project/commit/c6073d72ee23d8cd6aa49c08edde846359e41bde.diff

LOG: [LoopCacheAnalysis] Drop incorrect nowrap flags from addrec (#164796)

This patch stops propagating nowrap flags unconditionally. In the
modified part, when we have an addrec `{%a,+,%b}` where `%b` is known to
be negative, we create a new addrec `{%a,+,(-1 * %b)}`. When creating
it, the nowrap flags are transferred from the original addrec to the new
one without any checks, which is generally incorrect. Since the nowrap
property is not essential for this analysis, it would be better to drop
it to avoid potential bugs.

Added: 
    

Modified: 
    llvm/lib/Analysis/LoopCacheAnalysis.cpp

Removed: 
    


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diff  --git a/llvm/lib/Analysis/LoopCacheAnalysis.cpp b/llvm/lib/Analysis/LoopCacheAnalysis.cpp
index 050c32707596a..424a7fe3721bb 100644
--- a/llvm/lib/Analysis/LoopCacheAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopCacheAnalysis.cpp
@@ -436,10 +436,9 @@ bool IndexedReference::delinearize(const LoopInfo &LI) {
       const SCEV *StepRec = AccessFnAR ? AccessFnAR->getStepRecurrence(SE) : nullptr;
 
       if (StepRec && SE.isKnownNegative(StepRec))
-        AccessFn = SE.getAddRecExpr(AccessFnAR->getStart(),
-                                    SE.getNegativeSCEV(StepRec),
-                                    AccessFnAR->getLoop(),
-                                    AccessFnAR->getNoWrapFlags());
+        AccessFn = SE.getAddRecExpr(
+            AccessFnAR->getStart(), SE.getNegativeSCEV(StepRec),
+            AccessFnAR->getLoop(), SCEV::NoWrapFlags::FlagAnyWrap);
       const SCEV *Div = SE.getUDivExactExpr(AccessFn, ElemSize);
       Subscripts.push_back(Div);
       Sizes.push_back(ElemSize);