[llvm] [DA] Perform `nsw` check for SIV AddRecs earlier (NFCI) (PR #189740)

[Ehsan Amiri via llvm-commits]

https://github.com/amehsan updated https://github.com/llvm/llvm-project/pull/189740

>From 2614cf5835cf3dcb33b95b274bab4fbe3178ca84 Mon Sep 17 00:00:00 2001
From: Ehsan Amiri <ehsan.amiri at huawei.com>
Date: Tue, 31 Mar 2026 16:19:57 -0400
Subject: [PATCH 1/2] [DA] Perform `nsw` check for SIV AddRecs earlier (NFCI)

---
 llvm/lib/Analysis/DependenceAnalysis.cpp | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index abda00aba5812..17a3b92a65521 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -1228,9 +1228,6 @@ bool DependenceInfo::strongSIVtest(const SCEVAddRecExpr *Src,
   if (!isDependenceTestEnabled(DependenceTestType::StrongSIV))
     return false;
 
-  if (!Src->hasNoSignedWrap() || !Dst->hasNoSignedWrap())
-    return false;
-
   const SCEV *Coeff = Src->getStepRecurrence(*SE);
   assert(Coeff == Dst->getStepRecurrence(*SE) &&
          "Expecting same coefficient in Strong SIV test");
@@ -1370,9 +1367,6 @@ bool DependenceInfo::weakCrossingSIVtest(const SCEVAddRecExpr *Src,
   if (!isDependenceTestEnabled(DependenceTestType::WeakCrossingSIV))
     return false;
 
-  if (!Src->hasNoSignedWrap() || !Dst->hasNoSignedWrap())
-    return false;
-
   const SCEV *Coeff = Src->getStepRecurrence(*SE);
   const SCEV *SrcConst = Src->getStart();
   const SCEV *DstConst = Dst->getStart();
@@ -1629,9 +1623,6 @@ bool DependenceInfo::exactSIVtest(const SCEVAddRecExpr *Src,
   assert(0 < Level && Level <= CommonLevels && "Level out of range");
   Level--;
 
-  if (!Src->hasNoSignedWrap() || !Dst->hasNoSignedWrap())
-    return false;
-
   const SCEV *Delta = minusSCEVNoSignedOverflow(DstConst, SrcConst, *SE);
   if (!Delta)
     return false;
@@ -1774,9 +1765,6 @@ bool DependenceInfo::weakZeroSIVtestImpl(const SCEVAddRecExpr *AR,
   const SCEV *ARCoeff = AR->getStepRecurrence(*SE);
   const SCEV *ARConst = AR->getStart();
 
-  if (!AR->hasNoSignedWrap())
-    return false;
-
   if (Const == ARConst && SE->isKnownNonZero(ARCoeff)) {
     if (Level < CommonLevels) {
       Result.DV[Level].Direction &= Dependence::DVEntry::LE;
@@ -2061,7 +2049,9 @@ bool DependenceInfo::testSIV(const SCEV *Src, const SCEV *Dst, unsigned &Level,
   LLVM_DEBUG(dbgs() << "    dst = " << *Dst << "\n");
   const SCEVAddRecExpr *SrcAddRec = dyn_cast<SCEVAddRecExpr>(Src);
   const SCEVAddRecExpr *DstAddRec = dyn_cast<SCEVAddRecExpr>(Dst);
-  if (SrcAddRec && DstAddRec) {
+  bool SrcAnalyzable = SrcAddRec != nullptr && SrcAddRec->hasNoSignedWrap();
+  bool DstAnalyzable = DstAddRec != nullptr && DstAddRec->hasNoSignedWrap();
+  if (SrcAnalyzable && DstAnalyzable) {
     const SCEV *SrcCoeff = SrcAddRec->getStepRecurrence(*SE);
     const SCEV *DstCoeff = DstAddRec->getStepRecurrence(*SE);
     const Loop *CurSrcLoop = SrcAddRec->getLoop();
@@ -2078,17 +2068,18 @@ bool DependenceInfo::testSIV(const SCEV *Src, const SCEV *Dst, unsigned &Level,
       disproven = weakCrossingSIVtest(SrcAddRec, DstAddRec, Level, Result);
     return disproven || exactSIVtest(SrcAddRec, DstAddRec, Level, Result);
   }
-  if (SrcAddRec) {
+  if (SrcAnalyzable && DstAddRec == nullptr) {
     const Loop *CurSrcLoop = SrcAddRec->getLoop();
     Level = mapSrcLoop(CurSrcLoop);
     return weakZeroDstSIVtest(SrcAddRec, Dst, Level, Result);
   }
-  if (DstAddRec) {
+  if (DstAnalyzable && SrcAddRec == nullptr) {
     const Loop *CurDstLoop = DstAddRec->getLoop();
     Level = mapDstLoop(CurDstLoop);
     return weakZeroSrcSIVtest(Src, DstAddRec, Level, Result);
   }
-  llvm_unreachable("SIV test expected at least one AddRec");
+  assert(SrcAddRec != nullptr || DstAddRec != nullptr
+         && "SIV test expected at least one AddRec");
   return false;
 }
 

>From 8459c16874a46e6ef94cf0189ea2dd03b6e5cadb Mon Sep 17 00:00:00 2001
From: Ehsan Amiri <ehsan.amiri at huawei.com>
Date: Wed, 1 Apr 2026 14:00:39 -0400
Subject: [PATCH 2/2] fix code formatting issue

---
 llvm/lib/Analysis/DependenceAnalysis.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index b92618c475158..f2b55de7704a6 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -2081,8 +2081,8 @@ bool DependenceInfo::testSIV(const SCEV *Src, const SCEV *Dst, unsigned &Level,
     Level = mapDstLoop(CurDstLoop);
     return weakZeroSrcSIVtest(Src, DstAddRec, Level, Result);
   }
-  assert(SrcAddRec != nullptr || DstAddRec != nullptr
-         && "SIV test expected at least one AddRec");
+  assert(SrcAddRec != nullptr ||
+         DstAddRec != nullptr && "SIV test expected at least one AddRec");
   return false;
 }