[LLVM] Fix a bug in auto upgrading lifetime start/end intrinsics

[jurahul]

When creating the new intrinsic declaration, use the correct pointer argument (arg #1) from the existing call. Currently, we use arg #0 (size) and end up creating an invalid intrinsic declaration. However, later on we do not use this declaration directly and instead call CreateLifetimeStart or CreateLifetimeEnd IRBuilder functions that end up creating valid intrinsic declarations. The net result is that we are left with a stray unused invalid declaration.

Fix this issue by creating the intrinsic with the right pointer argument type.

[llvmorg-github-actions]

@llvm/pr-subscribers-llvm-ir

Author: Rahul Joshi (jurahul)

Changes

When creating the new intrinsic declaration, use the correct pointer argument (arg #1) from the existing call. Currently, we use arg #0 (size) and end up creating an invalid intrinsic declaration. However, later on we do not use this declaration directly and instead call CreateLifetimeStart or CreateLifetimeEnd IRBuilder functions that end up creating valid intrinsic declarations. The net result is that we are left with a stray unused invalid declaration.

Fix this issue by creating the intrinsic with the right pointer argument type.

---

Full diff: https://github.com/llvm/llvm-project/pull/204601.diff

2 Files Affected:

• (modified) llvm/lib/IR/AutoUpgrade.cpp (+3-1)
• (added) llvm/test/Assembler/autoupgrade-lifetime-intrinsics-invalid-decl.ll (+17)

diff --git a/llvm/lib/IR/AutoUpgrade.cpp b/llvm/lib/IR/AutoUpgrade.cpp
index 814e985ebf7be..4d353c95b8930 100644
--- a/llvm/lib/IR/AutoUpgrade.cpp
+++ b/llvm/lib/IR/AutoUpgrade.cpp
@@ -1556,8 +1556,10 @@ static bool upgradeIntrinsicFunction1(Function *F, Function *&NewFn,
                               ? Intrinsic::lifetime_start
                               : Intrinsic::lifetime_end;
       rename(F);
+      // Old 2 argument form of these intrinsics have [Size, Ptr] as arguments.
+      // Use the Ptr argument to create new declaration.
       NewFn = Intrinsic::getOrInsertDeclaration(F->getParent(), IID,
-                                                F->getArg(0)->getType());
+                                                F->getArg(1)->getType());
       return true;
     }
     break;
diff --git a/llvm/test/Assembler/autoupgrade-lifetime-intrinsics-invalid-decl.ll b/llvm/test/Assembler/autoupgrade-lifetime-intrinsics-invalid-decl.ll
new file mode 100644
index 0000000000000..dec73f40bb451
--- /dev/null
+++ b/llvm/test/Assembler/autoupgrade-lifetime-intrinsics-invalid-decl.ll
@@ -0,0 +1,17 @@
+; Test to verify that autoupgrade does not end up creating an invalid
+; declaration.
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+; CHECK-NOT: declare void @llvm.lifetime.start.i64(i64)
+; CHECK-NOT: declare void @llvm.lifetime.end.i64(i64)
+
+define void @tests.lifetime.start.end() {
+  %a = alloca i8
+  call void @llvm.lifetime.start(i64 1, ptr %a)
+  store i8 0, ptr %a
+  call void @llvm.lifetime.end(i64 1, ptr %a)
+  ret void
+}
+
+declare void @llvm.lifetime.start.p0(i64, ptr)
+declare void @llvm.lifetime.end.p0(i64, ptr)

[nikic]

LGTM