[llvm] [DA] Add overflow check when calculating Delta in GCD MIV (PR #169928)

[Ryotaro Kasuga via llvm-commits]

https://github.com/kasuga-fj updated https://github.com/llvm/llvm-project/pull/169928

>From 905e917cc5e5abe232b4df4e8c3eb1ffd822f252 Mon Sep 17 00:00:00 2001
From: Ryotaro Kasuga <kasuga.ryotaro at fujitsu.com>
Date: Fri, 28 Nov 2025 15:14:30 +0000
Subject: [PATCH] [DA] Add overflow check when calculating Delta in GCD MIV

---
 llvm/lib/Analysis/DependenceAnalysis.cpp                  | 4 +++-
 llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 253f4d1441098..c5353a36e4b5d 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -2582,7 +2582,9 @@ bool DependenceInfo::gcdMIVtest(const SCEV *Src, const SCEV *Dst,
   const SCEV *DstConst = Coefficients;
 
   APInt ExtraGCD = APInt::getZero(BitWidth);
-  const SCEV *Delta = SE->getMinusSCEV(DstConst, SrcConst);
+  const SCEV *Delta = minusSCEVNoSignedOverflow(DstConst, SrcConst, *SE);
+  if (!Delta)
+    return false;
   LLVM_DEBUG(dbgs() << "    Delta = " << *Delta << "\n");
   const SCEVConstant *Constant = dyn_cast<SCEVConstant>(Delta);
   if (const SCEVAddExpr *Sum = dyn_cast<SCEVAddExpr>(Delta)) {
diff --git a/llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll b/llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll
index 618d14c75faad..76bab98207c79 100644
--- a/llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll
@@ -89,7 +89,7 @@ define void @gcdmiv_delta_ovfl(ptr %A) {
 ; CHECK-GCD-MIV-NEXT:  Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 0, ptr %idx.0, align 1
 ; CHECK-GCD-MIV-NEXT:    da analyze - consistent output [*]!
 ; CHECK-GCD-MIV-NEXT:  Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
-; CHECK-GCD-MIV-NEXT:    da analyze - none!
+; CHECK-GCD-MIV-NEXT:    da analyze - consistent output [*|<]!
 ; CHECK-GCD-MIV-NEXT:  Src: store i8 1, ptr %idx.1, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
 ; CHECK-GCD-MIV-NEXT:    da analyze - consistent output [*]!
 ;