[llvm-branch-commits] [llvm] [DA] Remove absolute value calculations in the Weak Zero SIV tests (PR #185580)

[Ryotaro Kasuga via llvm-branch-commits]

https://github.com/kasuga-fj updated https://github.com/llvm/llvm-project/pull/185580

>From a2a37088be3cf2ef9e91b46d5daff1b7a282f078 Mon Sep 17 00:00:00 2001
From: Ryotaro Kasuga <kasuga.ryotaro at fujitsu.com>
Date: Mon, 9 Mar 2026 10:12:39 +0000
Subject: [PATCH] [DA] Remove absolute value calculations in the Weak Zero SIV
 tests

---
 llvm/lib/Analysis/DependenceAnalysis.cpp | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 9326534e954bd..797945b68f797 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -1817,19 +1817,19 @@ bool DependenceInfo::weakZeroSIVtestImpl(const SCEVAddRecExpr *AR,
   if (!ConstCoeff)
     return false;
 
-  // Since ConstCoeff is constant, !isKnownNegative means it's non-negative.
-  // TODO: Bail out if it's a signed minimum value.
-  const SCEV *AbsCoeff = SE->isKnownNegative(ConstCoeff)
-                             ? SE->getNegativeSCEV(ConstCoeff)
-                             : ConstCoeff;
   const SCEV *NewDelta =
       SE->isKnownNegative(ConstCoeff) ? SE->getNegativeSCEV(Delta) : Delta;
 
   if (const SCEV *UpperBound =
           collectUpperBound(AR->getLoop(), Delta->getType())) {
     LLVM_DEBUG(dbgs() << "\t    UpperBound = " << *UpperBound << "\n");
-    const SCEV *Product = SE->getMulExpr(AbsCoeff, UpperBound);
-    if (SE->isKnownPredicate(CmpInst::ICMP_EQ, NewDelta, Product)) {
+    bool OverlapAtLast = [&] {
+      if (!SE->isKnownNonZero(ConstCoeff))
+        return false;
+      const SCEV *Last = AR->evaluateAtIteration(UpperBound, *SE);
+      return Last == Const;
+    }();
+    if (OverlapAtLast) {
       // dependences caused by last iteration
       if (Level < CommonLevels) {
         Result.DV[Level].Direction &= Dependence::DVEntry::GE;