[llvm] [ObjCARC] Delete empty autoreleasepools with no autoreleases in them (PR #144788)

[via llvm-commits]

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@@ -0,0 +1,79 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; Test for autorelease pool optimizations
+; RUN: opt -passes=objc-arc < %s -S | FileCheck %s
+
+declare ptr @llvm.objc.autoreleasePoolPush()
+declare void @llvm.objc.autoreleasePoolPop(ptr)
+declare ptr @llvm.objc.autorelease(ptr)
+declare ptr @llvm.objc.retain(ptr)
+declare ptr @create_object()
+declare void @use_object(ptr)
+declare ptr @object_with_thing()
+
+; Test 1: Empty autorelease pool should be eliminated
+define void @test_empty_pool() {
+; CHECK-LABEL: define void @test_empty_pool() {
+; CHECK-NEXT:    ret void
+;
+  %pool = call ptr @llvm.objc.autoreleasePoolPush()
+  call void @llvm.objc.autoreleasePoolPop(ptr %pool)
+  ret void
+}
+
+; Test 2: Pool with only release should be removed
+define void @test_autorelease_to_release() {
+; CHECK-LABEL: define void @test_autorelease_to_release() {
+; CHECK-NEXT:    [[OBJ:%.*]] = call ptr @create_object()
+; CHECK-NEXT:    call void @llvm.objc.release(ptr [[OBJ]]) #[[ATTR0:[0-9]+]], !clang.imprecise_release [[META0:![0-9]+]]
+; CHECK-NEXT:    ret void
+;
+  %obj = call ptr @create_object()
+  %pool = call ptr @llvm.objc.autoreleasePoolPush()
+  call ptr @llvm.objc.autorelease(ptr %obj)
+  call void @llvm.objc.autoreleasePoolPop(ptr %pool)
+  ret void
+}
+
+; Test 3: Pool with autoreleases should not be optimized
+define void @test_multiple_autoreleases() {
+; CHECK-LABEL: define void @test_multiple_autoreleases() {
+; CHECK-NEXT:    [[OBJ1:%.*]] = call ptr @create_object()
+; CHECK-NEXT:    [[OBJ2:%.*]] = call ptr @create_object()
+; CHECK-NEXT:    [[POOL:%.*]] = call ptr @llvm.objc.autoreleasePoolPush() #[[ATTR0]]
+; CHECK-NEXT:    call void @use_object(ptr [[OBJ1]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call ptr @llvm.objc.autorelease(ptr [[OBJ1]]) #[[ATTR0]]
+; CHECK-NEXT:    call void @use_object(ptr [[OBJ2]])
+; CHECK-NEXT:    [[TMP2:%.*]] = call ptr @llvm.objc.autorelease(ptr [[OBJ2]]) #[[ATTR0]]
+; CHECK-NEXT:    call void @llvm.objc.autoreleasePoolPop(ptr [[POOL]]) #[[ATTR0]]
+; CHECK-NEXT:    ret void
+;
+  %obj1 = call ptr @create_object()
+  %obj2 = call ptr @create_object()
+  %pool = call ptr @llvm.objc.autoreleasePoolPush()
+  call void @use_object(ptr %obj1)
+  call ptr @llvm.objc.autorelease(ptr %obj1)
+  call void @use_object(ptr %obj2)
+  call ptr @llvm.objc.autorelease(ptr %obj2)
+  call void @llvm.objc.autoreleasePoolPop(ptr %pool)
+  ret void
+}
+
+; Test 4: Pool with calls should not be optimized
+define void @test_calls() {
+; CHECK-LABEL: define void @test_calls() {
+; CHECK-NEXT:    [[POOL:%.*]] = call ptr @llvm.objc.autoreleasePoolPush() #[[ATTR0]]
+; CHECK-NEXT:    [[OBJ1:%.*]] = call ptr @object_with_thing()
+; CHECK-NEXT:    call void @use_object(ptr [[OBJ1]])
+; CHECK-NEXT:    call void @llvm.objc.autoreleasePoolPop(ptr [[POOL]]) #[[ATTR0]]
+; CHECK-NEXT:    ret void
+;
+  %pool = call ptr @llvm.objc.autoreleasePoolPush()
+  %obj1 = call ptr @object_with_thing()
+  call void @use_object(ptr %obj1)
+  call void @llvm.objc.autoreleasePoolPop(ptr %pool)
+  ret void
+}
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AZero13 wrote:

Question: do you expect this to prevent optimization or not? because there is no object being passed but in an opaque callee I feel like anything can happen so let's be safe.

https://github.com/llvm/llvm-project/pull/144788