[DA] Add overflow check when calculating Delta in GCD MIV

[kasuga-fj]

Add overflow check when computing Delta in gcdMIVtest.

Fix one of the tests added by #169926.

[kasuga-fj]

• [DA] Add overflow check when calculating Delta in GCD MIV #169928 👈 (View in Graphite)
• [DA] Add tests for GCD MIV misses dependency due to overflow (NFC) #169926 : 1 other dependent PR (#169927 )
• main

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[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Ryotaro Kasuga (kasuga-fj)

Changes

Add overflow check when computing Delta in gcdMIVtest.

Fix one of the tests added by #169926.

---

Full diff: https://github.com/llvm/llvm-project/pull/169928.diff

2 Files Affected:

• (modified) llvm/lib/Analysis/DependenceAnalysis.cpp (+3-1)
• (modified) llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll (+1-1)

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 77b09fb15316e..73a7b59c81f27 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -2587,7 +2587,9 @@ 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 [*]!
 ;

[Meinersbur]

LGTM