[CodeGen][GC] Skip function without GC in GCLoweringPass

[paperchalice]

No description provided.

[aeubanks]

is this purely a compile time optimization? or does this actually have functional change (in which case should have a test)

[paperchalice]

is this purely a compile time optimization? or does this actually have functional change (in which case should have a test)

It is a pass to lower GC intrinsics, GC related passes are lack of testing.

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: None (paperchalice)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/84421.diff

2 Files Affected:

• (modified) llvm/lib/CodeGen/GCRootLowering.cpp (+3)
• (modified) llvm/test/CodeGen/X86/GC/alloc_loop.ll (+7)

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());
diff --git a/llvm/test/CodeGen/X86/GC/alloc_loop.ll b/llvm/test/CodeGen/X86/GC/alloc_loop.ll
index 4b7230fee9c5a9..4e87735e830ffe 100644
--- a/llvm/test/CodeGen/X86/GC/alloc_loop.ll
+++ b/llvm/test/CodeGen/X86/GC/alloc_loop.ll
@@ -1,4 +1,5 @@
 ; RUN: llc -mtriple=x86_64 < %s
+; 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)
@@ -31,6 +32,8 @@ entry:
 	%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-NOT: call void @llvm.gcwrite(ptr %A.1, ptr %B.upgrd.1, ptr %B.1)
+	; CHECK: store ptr %A.1, ptr %B.1, align 8
 	
 	br label %AllocLoop
 
@@ -47,4 +50,8 @@ Exit:
 	ret i32 0
 }
 
+define void @no_gc() {
+	ret void
+}
+
 declare void @__main()

[paperchalice]

Find a place to add related test.

[arsenm]

-NOT checks are perilous and should be as lax as possible. Better would be -NEXT checks to show it's not present

[paperchalice]

Move test to CodeGen/Generic, and use CHECK-NEXT.

[arsenm]

test whitespace is weird

[paperchalice]

Oops, mix tab and space.

[aeubanks]

use llvm/utils/update_test_checks.py for the test?