[llvm] ObjCARCContract: Use stripPointerCastsAndAliases (PR #134275)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/134275

>From de0d4747fefa249c26ff46ccac85e15fde354683 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Thu, 3 Apr 2025 23:44:32 +0700
Subject: [PATCH 1/2] ObjCARCContract: Use stripPointerCastsAndAliases

---
 .../Transforms/ObjCARC/ObjCARCContract.cpp    | 34 ++++++-------------
 1 file changed, 10 insertions(+), 24 deletions(-)

diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
index e11748b2c9dbb..ed7a235f5e2e3 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
@@ -661,30 +661,16 @@ bool ObjCARCContract::run(Function &F, AAResults *A, DominatorTree *D) {
 
     Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
 
-    // TODO: Change this to a do-while.
-    for (;;) {
-      ReplaceArgUses(Arg);
-
-      // If Arg is a no-op casted pointer, strip one level of casts and iterate.
-      if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
-        Arg = BI->getOperand(0);
-      else if (isa<GEPOperator>(Arg) &&
-               cast<GEPOperator>(Arg)->hasAllZeroIndices())
-        Arg = cast<GEPOperator>(Arg)->getPointerOperand();
-      else if (isa<GlobalAlias>(Arg) &&
-               !cast<GlobalAlias>(Arg)->isInterposable())
-        Arg = cast<GlobalAlias>(Arg)->getAliasee();
-      else {
-        // If Arg is a PHI node, get PHIs that are equivalent to it and replace
-        // their uses.
-        if (PHINode *PN = dyn_cast<PHINode>(Arg)) {
-          SmallVector<Value *, 1> PHIList;
-          getEquivalentPHIs(*PN, PHIList);
-          for (Value *PHI : PHIList)
-            ReplaceArgUses(PHI);
-        }
-        break;
-      }
+    ReplaceArgUses(Arg);
+
+    Arg = Arg->stripPointerCastsAndAliases();
+    // If Arg is a PHI node, get PHIs that are equivalent to it and replace
+    // their uses.
+    if (PHINode *PN = dyn_cast<PHINode>(Arg)) {
+      SmallVector<Value *, 1> PHIList;
+      getEquivalentPHIs(*PN, PHIList);
+      for (Value *PHI : PHIList)
+        ReplaceArgUses(PHI);
     }
   }
 

>From cfd252525aa84e2f8c6f9f7a1daf66ad21f65bd9 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Sat, 12 Apr 2025 09:09:04 +0200
Subject: [PATCH 2/2] Fix new test

---
 llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp |  8 +++++---
 llvm/test/Transforms/ObjCARC/contract.ll        | 16 ++++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
index ed7a235f5e2e3..79d04bfa57d74 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
@@ -660,13 +660,15 @@ bool ObjCARCContract::run(Function &F, AAResults *A, DominatorTree *D) {
     };
 
     Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
-
     ReplaceArgUses(Arg);
 
-    Arg = Arg->stripPointerCastsAndAliases();
+    Value *Stripped = Arg->stripPointerCastsAndAliases();
+    if (Stripped != Arg)
+      ReplaceArgUses(Stripped);
+
     // If Arg is a PHI node, get PHIs that are equivalent to it and replace
     // their uses.
-    if (PHINode *PN = dyn_cast<PHINode>(Arg)) {
+    if (PHINode *PN = dyn_cast<PHINode>(Stripped)) {
       SmallVector<Value *, 1> PHIList;
       getEquivalentPHIs(*PN, PHIList);
       for (Value *PHI : PHIList)
diff --git a/llvm/test/Transforms/ObjCARC/contract.ll b/llvm/test/Transforms/ObjCARC/contract.ll
index 70bd57a0c719a..24f9a712ccd0a 100644
--- a/llvm/test/Transforms/ObjCARC/contract.ll
+++ b/llvm/test/Transforms/ObjCARC/contract.ll
@@ -234,6 +234,22 @@ define void @test14(ptr %a, ptr %b) {
   ret void
 }
 
+define void @test15(ptr %x) {
+; CHECK-LABEL: define void @test15(
+; CHECK-SAME: ptr [[X:%.*]]) {
+; CHECK-NEXT:    [[Y:%.*]] = getelementptr inbounds ptr, ptr [[X]], i32 0
+; CHECK-NEXT:    [[V0:%.*]] = call ptr @llvm.objc.retain(ptr [[Y]]) #[[ATTR0:[0-9]+]]
+; CHECK-NEXT:    call void @use_pointer(ptr [[V0]])
+; CHECK-NEXT:    call void @use_pointer(ptr [[V0]])
+; CHECK-NEXT:    ret void
+;
+  %y = getelementptr inbounds ptr, ptr %x, i32 0
+  %v0 = call ptr @llvm.objc.retain(ptr %y) nounwind
+  call void @use_pointer(ptr %x)
+  call void @use_pointer(ptr %y)
+  ret void
+}
+
 declare void @llvm.objc.clang.arc.use(...) nounwind
 declare void @llvm.objc.clang.arc.noop.use(...) nounwind