[llvm] [LAA] Get conflicts in loop-invariant addresses (PR #180945)

[Raphael Moreira Zinsly via llvm-commits]

https://github.com/rzinsly created https://github.com/llvm/llvm-project/pull/180945

This is part of the work tracked in #168312.
In preparation to #165312, add the ability to gather the pairs of load and store that conflicts by accessing the same IV address.

Co-Authored-By: Felipe Magno de Almeida <felipe at expertise.dev>

>From fdea554a8d5fe753bc211c7156bc1bf4d3ce445c Mon Sep 17 00:00:00 2001
From: Raphael Moreira Zinsly <raphael.zinsly at oss.qualcomm.com>
Date: Wed, 11 Feb 2026 10:40:38 -0300
Subject: [PATCH] [LAA] Get conflicts between loop-invariant addresses

In preparation to #165312, add the ability to gather the pairs of load
and store that conflicts by accessing the same IV address.

Co-Authored-By: Felipe Magno de Almeida <felipe at expertise.dev>
---
 llvm/include/llvm/Analysis/LoopAccessAnalysis.h |  9 +++++++++
 llvm/lib/Analysis/LoopAccessAnalysis.cpp        | 15 +++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/llvm/include/llvm/Analysis/LoopAccessAnalysis.h b/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
index c85ef3e131068..3016b7e5cec36 100644
--- a/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
+++ b/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
@@ -775,6 +775,12 @@ class LoopAccessInfo {
     return StoresToInvariantAddresses;
   }
 
+  /// Returns conflicts between loads and stores to invariant addresses.
+  ArrayRef<std::pair<LoadInst *, StoreInst *>>
+  getInvariantAddressConflicts() const {
+    return InvariantAddressConflicts;
+  }
+
   /// Used to add runtime SCEV checks. Simplifies SCEV expressions and converts
   /// them to a more usable form.  All SCEV expressions during the analysis
   /// should be re-written (and therefore simplified) according to PSE.
@@ -853,6 +859,9 @@ class LoopAccessInfo {
   /// List of stores to invariant addresses.
   SmallVector<StoreInst *> StoresToInvariantAddresses;
 
+  /// List of conflict pair due to accessing the same loop-invariant address.
+  SmallVector<std::pair<LoadInst *, StoreInst *>> InvariantAddressConflicts;
+
   /// The diagnostics report generated for the analysis.  E.g. why we
   /// couldn't analyze the loop.
   std::unique_ptr<OptimizationRemarkAnalysis> Report;
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index eae645ab84fff..87c8ea89ff9ac 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -2685,6 +2685,21 @@ bool LoopAccessInfo::analyzeLoop(AAResults *AA, const LoopInfo *LI,
     }
   }
 
+  // Gather the loop-invariant address with conflicts.
+  for (LoadInst *LD : Loads) {
+    Value *Ptr = LD->getPointerOperand();
+    if (UniformStores.contains(Ptr)) {
+      if (TheLoop->isLoopInvariant(LD->getPointerOperand())) {
+        for (StoreInst *ST : StoresToInvariantAddresses) {
+          if (ST->getPointerOperand() == Ptr) {
+            InvariantAddressConflicts.emplace_back(LD, ST);
+            break;
+          }
+        }
+      }
+    }
+  }
+
   if (IsAnnotatedParallel) {
     LLVM_DEBUG(
         dbgs() << "LAA: A loop annotated parallel, ignore memory dependency "