[llvm] MemoryDependenceAnalysis: Consider a pointer clobbered if it is saved (PR #142096)

[YunQiang Su via llvm-commits]

https://github.com/wzssyqa created https://github.com/llvm/llvm-project/pull/142096

In MemoryDependenceResults::getSimplePointerDependencyFrom, when we find the instruction that a LoadInst depends, if we find an store instruction that save the pointer used by LoadInst, we consider the pointer may be clobbered.

>From ebd9e35af9091338a5abdb5a499f5f68a6df9eea Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Fri, 30 May 2025 15:05:30 +0800
Subject: [PATCH] MemoryDependenceAnalysis: Consider a pointer clobbered if it
 is saved

In MemoryDependenceResults::getSimplePointerDependencyFrom, when
we find the instruction that a LoadInst depends, if we find an
store instruction that save the pointer used by LoadInst, we consider
the pointer may be clobbered.
---
 llvm/lib/Analysis/MemoryDependenceAnalysis.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index f062189bac6a0..00f36b9e088ad 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -564,6 +564,11 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
         if (!QueryInst || QueryInst->isVolatile())
           return MemDepResult::getClobber(SI);
 
+      // If we store the pointer of QueryInst, it is danger due to that the address
+      // may be modified with other reference.
+      if (QueryInst && QueryInst->getOperand(0) == SI->getOperand(0))
+        return MemDepResult::getClobber(SI);
+
       // If alias analysis can tell that this store is guaranteed to not modify
       // the query pointer, ignore it.  Use getModRefInfo to handle cases where
       // the query pointer points to constant memory etc.