From 84717a78a3482a4d969c3e4fd9196f86a6870c7d Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Fri, 24 Mar 2023 14:17:26 +0100
Subject: [PATCH] [GlobalOpt] Fix dead const handling in pointer root user
 cleanup (PR61674)

Rather than cleanup up dead constant expressions as we go along,
do this once at the end. This aligns it with the
CleanupConstantGlobalUsers() implementation and avoids
any invalidation issues.

Fixes https://github.com/llvm/llvm-project/issues/61674.
---
 llvm/lib/Transforms/IPO/GlobalOpt.cpp     | 14 ++------------
 llvm/test/Transforms/GlobalOpt/pr61674.ll | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 12 deletions(-)
 create mode 100644 llvm/test/Transforms/GlobalOpt/pr61674.ll

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 1d5661119df8..fec8d7032916 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -237,19 +237,8 @@ CleanupPointerRootUsers(GlobalVariable *GV,
           Dead.push_back(std::make_pair(I, MTI));
       }
     } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
-      if (CE->use_empty()) {
-        CE->destroyConstant();
-        Changed = true;
-      } else if (isa<GEPOperator>(CE))
+      if (isa<GEPOperator>(CE))
         append_range(Worklist, CE->users());
-    } else if (Constant *C = dyn_cast<Constant>(U)) {
-      if (isSafeToDestroyConstant(C)) {
-        C->destroyConstant();
-        // This could have invalidated UI, start over from scratch.
-        Dead.clear();
-        CleanupPointerRootUsers(GV, GetTLI);
-        return true;
-      }
     }
   }
 
@@ -271,6 +260,7 @@ CleanupPointerRootUsers(GlobalVariable *GV,
     }
   }
 
+  GV->removeDeadConstantUsers();
   return Changed;
 }
 
diff --git a/llvm/test/Transforms/GlobalOpt/pr61674.ll b/llvm/test/Transforms/GlobalOpt/pr61674.ll
new file mode 100644
index 000000000000..1ca86345107b
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/pr61674.ll
@@ -0,0 +1,21 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -S -passes=globalopt < %s | FileCheck %s
+
+; Test handling of dead constant expressions in CleanupPointerRootUsers().
+
+@g = internal global [2 x [1 x [6 x ptr]]] zeroinitializer
+
+define void @test() {
+; CHECK-LABEL: define void @test() local_unnamed_addr {
+; CHECK-NEXT:    ret void
+;
+  store ptr null, ptr getelementptr inbounds ([2 x [1 x [6 x ptr]]], ptr @g, i32 0, i32 1), align 1
+  ret void
+
+dead:
+  zext i1 icmp ne (ptr getelementptr inbounds ([2 x [1 x [6 x ptr]]], ptr @g, i32 0, i32 1), ptr getelementptr inbounds ([6 x ptr], ptr getelementptr inbounds ([2 x [1 x [6 x ptr]]], ptr @g, i32 0, i32 1), i32 0, i32 5)) to i16
+  ret void
+}
+
+; uselistorder directives
+uselistorder ptr getelementptr inbounds ([2 x [1 x [6 x ptr]]], ptr @g, i32 0, i32 1), { 1, 2, 0 }
-- 
2.34.1