[llvm] [DSE] Check write location in IsRedundantStore (PR #93400)

[via llvm-commits]

https://github.com/eaeltsin updated https://github.com/llvm/llvm-project/pull/93400

>From 385e1e6b34bf7b169e33440dcbaa4051437baf55 Mon Sep 17 00:00:00 2001
From: Evgeny Eltsin <eaeltsin at google.com>
Date: Sun, 26 May 2024 05:48:41 +0000
Subject: [PATCH 1/2] [DSE] Check write location in IsRedundantStore

---
 llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index ed4212d29cef7..172cce2cfa381 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -2109,10 +2109,12 @@ struct DSEState {
         if (auto *MemSetI = dyn_cast<MemSetInst>(UpperInst)) {
           if (auto *SI = dyn_cast<StoreInst>(DefInst)) {
             // MemSetInst must have a write location.
-            MemoryLocation UpperLoc = *getLocForWrite(UpperInst);
+            auto UpperLoc = getLocForWrite(UpperInst);
+            if (!UpperLoc)
+              return false;
             int64_t InstWriteOffset = 0;
             int64_t DepWriteOffset = 0;
-            auto OR = isOverwrite(UpperInst, DefInst, UpperLoc, *MaybeDefLoc,
+            auto OR = isOverwrite(UpperInst, DefInst, *UpperLoc, *MaybeDefLoc,
                                   InstWriteOffset, DepWriteOffset);
             Value *StoredByte = isBytewiseValue(SI->getValueOperand(), DL);
             return StoredByte && StoredByte == MemSetI->getOperand(1) &&

>From 04549d9bce9be636fa8dc6dbf574c0bfab27752e Mon Sep 17 00:00:00 2001
From: Evgeny Eltsin <eaeltsin at google.com>
Date: Sun, 26 May 2024 18:30:22 +0000
Subject: [PATCH 2/2] [DSE] Add test on null write location

---
 llvm/test/Transforms/DeadStoreElimination/simple.ll | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/llvm/test/Transforms/DeadStoreElimination/simple.ll b/llvm/test/Transforms/DeadStoreElimination/simple.ll
index e5d3dd09fa148..ef2c4ef564b24 100644
--- a/llvm/test/Transforms/DeadStoreElimination/simple.ll
+++ b/llvm/test/Transforms/DeadStoreElimination/simple.ll
@@ -790,3 +790,16 @@ define i32 @test48(ptr %P, ptr noalias %Q, ptr %R) {
   %l = load i32, ptr %R
   ret i32 %l
 }
+
+define void @test49() {
+; CHECK-LABEL: @test49(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr readonly null, i8 0, i64 0, i1 false)
+; CHECK-NEXT:    store ptr null, ptr null, align 8
+; CHECK-NEXT:    ret void
+;
+bb:
+  call void @llvm.memset.p0.i64(ptr readonly null, i8 0, i64 0, i1 false)
+  store ptr null, ptr null, align 8
+  ret void
+}