[llvm] [CodeGen][GC] Skip function without GC in `GCLoweringPass` (PR #84421)

[via llvm-commits]

https://github.com/paperchalice updated https://github.com/llvm/llvm-project/pull/84421

>From e1668c840819c5ff2ebe28424bcd54a9a2abc484 Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Fri, 8 Mar 2024 10:14:00 +0800
Subject: [PATCH 1/2] [CodeGen][GC] Skip function without GC in
 `GCLoweringPass`

---
 llvm/lib/CodeGen/GCRootLowering.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/lib/CodeGen/GCRootLowering.cpp b/llvm/lib/CodeGen/GCRootLowering.cpp
index 894ab9a0486a7b..0d82f2bab8960b 100644
--- a/llvm/lib/CodeGen/GCRootLowering.cpp
+++ b/llvm/lib/CodeGen/GCRootLowering.cpp
@@ -81,6 +81,9 @@ class GCMachineCodeAnalysis : public MachineFunctionPass {
 
 PreservedAnalyses GCLoweringPass::run(Function &F,
                                       FunctionAnalysisManager &FAM) {
+  if (!F.hasGC())
+    return PreservedAnalyses::all();
+
   auto &Info = FAM.getResult<GCFunctionAnalysis>(F);
 
   bool Changed = DoLowering(F, Info.getStrategy());

>From 28071e020df3e6634e9f75540401c1e365bf508f Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Fri, 8 Mar 2024 14:16:12 +0800
Subject: [PATCH 2/2] add test

---
 llvm/test/CodeGen/Generic/gc-lowering.ll | 42 ++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 llvm/test/CodeGen/Generic/gc-lowering.ll

diff --git a/llvm/test/CodeGen/Generic/gc-lowering.ll b/llvm/test/CodeGen/Generic/gc-lowering.ll
new file mode 100644
index 00000000000000..7297db8c105510
--- /dev/null
+++ b/llvm/test/CodeGen/Generic/gc-lowering.ll
@@ -0,0 +1,42 @@
+; RUN: opt -S -passes='require<collector-metadata>,function(gc-lowering)' < %s | FileCheck %s
+
+declare ptr @llvm_gc_allocate(i32)
+declare void @llvm_gc_initialize(i32)
+
+declare void @llvm.gcroot(ptr, ptr)
+declare void @llvm.gcwrite(ptr, ptr, ptr)
+
+define i32 @main() gc "shadow-stack" {
+entry:
+	%A = alloca ptr
+	%B = alloca ptr
+
+	call void @llvm_gc_initialize(i32 1048576)  ; Start with 1MB heap
+
+        ;; ptr A;
+	call void @llvm.gcroot(ptr %A, ptr null)
+
+        ;; A = gcalloc(10);
+	%Aptr = call ptr @llvm_gc_allocate(i32 10)
+	store ptr %Aptr, ptr %A
+
+        ;; ptr B;
+	call void @llvm.gcroot(ptr %B, ptr null)
+
+	;; B = gcalloc(4);
+	%B.upgrd.1 = call ptr @llvm_gc_allocate(i32 8)
+	store ptr %B.upgrd.1, ptr %B
+
+	;; *B = A;
+	%B.1 = load ptr, ptr %B
+	%A.1 = load ptr, ptr %A
+	call void @llvm.gcwrite(ptr %A.1, ptr %B.upgrd.1, ptr %B.1)
+	; CHECK: 			%A.1 = load ptr, ptr %A, align 8
+	; CHECK-NEXT: store ptr %A.1, ptr %B.1, align 8
+
+  ret i32 0
+}
+
+define void @no_gc() {
+	ret void
+}