28fe9afdba
that release the retained object This patch fixes what looks like a longstanding bug in ARC optimizer where it reverses the order of objc_retain calls and objc_release calls that retain and release the same object. The code in ARC optimizer that is responsible for code motion takes the following steps: 1. Traverse the CFG bottom-up and determine how far up objc_release calls can be moved. Determine the insertion points for the objc_release calls, but don't actually move them. 2. Traverse the CFG top-down and determine how far down objc_retain calls can be moved. Determine the insertion points for the objc_retain calls, but don't actually move them. 3. Try to move the objc_retain and objc_release calls if they can't be removed. The problem is that the insertion points for the objc_retain calls are determined in step 2 without taking into consideration the insertion points for objc_release calls determined in step 1, so the order of an objc_retain call and an objc_release call can be reversed, which is incorrect, even though each step is correct in isolation. To fix this bug, this patch teaches the top-down traversal step to take into consideration the insertion points for objc_release calls determined in the bottom-up traversal step. Code motion for an objc_retain call is disabled if there is a possibility that it can be moved past an objc_release call that releases the retained object. rdar://79292791 Differential Revision: https://reviews.llvm.org/D104953
204 lines
6.6 KiB
LLVM
204 lines
6.6 KiB
LLVM
; RUN: opt -objc-arc -S < %s | FileCheck %s
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declare void @alterRefCount()
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declare void @use(i8*)
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declare void @readOnlyFunc(i8*, i8*)
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@g0 = global i8* null, align 8
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; Check that ARC optimizer doesn't reverse the order of the retain call and the
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; release call when there are debug instructions.
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; CHECK: call i8* @llvm.objc.retain(i8* %x)
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; CHECK: call void @llvm.objc.release(i8* %x)
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define i32 @test(i8* %x, i8* %y, i8 %z, i32 %i) {
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%i.addr = alloca i32, align 4
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store i32 %i, i32* %i.addr, align 4
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%v1 = tail call i8* @llvm.objc.retain(i8* %x)
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store i8 %z, i8* %x
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call void @llvm.dbg.declare(metadata i32* %i.addr, metadata !9, metadata !DIExpression()), !dbg !10
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call void @alterRefCount()
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tail call void @llvm.objc.release(i8* %x)
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ret i32 %i
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}
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; ARC optimizer shouldn't move the release call, which is a precise release call
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; past the call to @alterRefCount.
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; CHECK-LABEL: define void @test2(
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; CHECK: call void @alterRefCount(
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; CHECK: call void @llvm.objc.release(
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define void @test2() {
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%v0 = load i8*, i8** @g0, align 8
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%v1 = tail call i8* @llvm.objc.retain(i8* %v0)
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tail call void @use(i8* %v0)
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tail call void @alterRefCount()
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tail call void @llvm.objc.release(i8* %v0)
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ret void
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}
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; Check that code motion is disabled in @test3 and @test4.
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; Previously, ARC optimizer would move the release past the retain.
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; if.then:
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; call void @readOnlyFunc(i8* %obj, i8* null)
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; call void @llvm.objc.release(i8* %obj) #1, !clang.imprecise_release !2
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; %1 = add i32 1, 2
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; %2 = tail call i8* @llvm.objc.retain(i8* %obj)
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;
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; Ideally, the retain/release pairs in BB if.then should be removed.
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define void @test3(i8* %obj, i1 %cond) {
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; CHECK-LABEL: @test3(
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; CHECK-NEXT: [[TMP2:%.*]] = tail call i8* @llvm.objc.retain(i8* [[OBJ:%.*]])
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; CHECK-NEXT: br i1 [[COND:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: call void @readOnlyFunc(i8* [[OBJ]], i8* null)
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; CHECK-NEXT: [[TMP1:%.*]] = add i32 1, 2
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; CHECK-NEXT: call void @alterRefCount()
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; CHECK-NEXT: br label [[JOIN:%.*]]
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; CHECK: if.else:
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; CHECK-NEXT: call void @alterRefCount()
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; CHECK-NEXT: call void @use(i8* [[OBJ]])
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; CHECK-NEXT: br label [[JOIN]]
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; CHECK: join:
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; CHECK-NEXT: call void @llvm.objc.release(i8* [[OBJ]]) {{.*}}, !clang.imprecise_release !2
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; CHECK-NEXT: ret void
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;
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%v0 = call i8* @llvm.objc.retain(i8* %obj)
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br i1 %cond, label %if.then, label %if.else
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if.then:
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call void @readOnlyFunc(i8* %obj, i8* null) #0
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add i32 1, 2
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call void @alterRefCount()
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br label %join
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if.else:
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call void @alterRefCount()
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call void @use(i8* %obj)
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br label %join
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join:
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call void @llvm.objc.release(i8* %obj), !clang.imprecise_release !9
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ret void
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}
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define void @test4(i8* %obj0, i8* %obj1, i1 %cond) {
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; CHECK-LABEL: @test4(
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; CHECK-NEXT: [[TMP3:%.*]] = tail call i8* @llvm.objc.retain(i8* [[OBJ0:%.*]])
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; CHECK-NEXT: [[TMP2:%.*]] = tail call i8* @llvm.objc.retain(i8* [[OBJ1:%.*]])
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; CHECK-NEXT: br i1 [[COND:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: call void @readOnlyFunc(i8* [[OBJ0]], i8* [[OBJ1]])
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; CHECK-NEXT: [[TMP1:%.*]] = add i32 1, 2
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; CHECK-NEXT: call void @alterRefCount()
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; CHECK-NEXT: br label [[JOIN:%.*]]
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; CHECK: if.else:
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; CHECK-NEXT: call void @alterRefCount()
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; CHECK-NEXT: call void @use(i8* [[OBJ0]])
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; CHECK-NEXT: call void @use(i8* [[OBJ1]])
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; CHECK-NEXT: br label [[JOIN]]
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; CHECK: join:
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; CHECK-NEXT: call void @llvm.objc.release(i8* [[OBJ0]]) {{.*}}, !clang.imprecise_release !2
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; CHECK-NEXT: call void @llvm.objc.release(i8* [[OBJ1]]) {{.*}}, !clang.imprecise_release !2
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; CHECK-NEXT: ret void
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;
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%v0 = call i8* @llvm.objc.retain(i8* %obj0)
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%v1 = call i8* @llvm.objc.retain(i8* %obj1)
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br i1 %cond, label %if.then, label %if.else
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if.then:
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call void @readOnlyFunc(i8* %obj0, i8* %obj1) #0
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add i32 1, 2
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call void @alterRefCount()
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br label %join
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if.else:
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call void @alterRefCount()
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call void @use(i8* %obj0)
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call void @use(i8* %obj1)
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br label %join
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join:
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call void @llvm.objc.release(i8* %obj0), !clang.imprecise_release !9
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call void @llvm.objc.release(i8* %obj1), !clang.imprecise_release !9
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ret void
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}
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; In this test, insertion points for the retain and release calls that could be
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; eliminated are in different blocks (bb1 and if.then).
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define void @test5(i8* %obj, i1 %cond0, i1 %cond1) {
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; CHECK-LABEL: @test5(
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; CHECK-NEXT: [[V0:%.*]] = tail call i8* @llvm.objc.retain(i8* [[OBJ:%.*]])
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; CHECK-NEXT: br i1 [[COND0:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: call void @readOnlyFunc(i8* [[OBJ]], i8* null)
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; CHECK-NEXT: br i1 [[COND1:%.*]], label [[IF_THEN2:%.*]], label [[IF_ELSE2:%.*]]
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; CHECK: if.then2:
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; CHECK-NEXT: br label [[BB1:%.*]]
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; CHECK: if.else2:
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; CHECK-NEXT: br label [[BB1]]
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; CHECK: bb1:
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; CHECK-NEXT: [[TMP1:%.*]] = add i32 1, 2
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; CHECK-NEXT: call void @alterRefCount()
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; CHECK-NEXT: br label [[JOIN:%.*]]
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; CHECK: if.else:
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; CHECK-NEXT: call void @alterRefCount()
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; CHECK-NEXT: call void @use(i8* [[OBJ]])
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; CHECK-NEXT: br label [[JOIN]]
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; CHECK: join:
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; CHECK-NEXT: call void @llvm.objc.release(i8* [[OBJ]])
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; CHECK-NEXT: ret void
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;
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%v0 = call i8* @llvm.objc.retain(i8* %obj)
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br i1 %cond0, label %if.then, label %if.else
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if.then:
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call void @readOnlyFunc(i8* %obj, i8* null) #0
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br i1 %cond1, label %if.then2, label %if.else2
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if.then2:
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br label %bb1
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if.else2:
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br label %bb1
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bb1:
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add i32 1, 2
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call void @alterRefCount()
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br label %join
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if.else:
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call void @alterRefCount()
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call void @use(i8* %obj)
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br label %join
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join:
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call void @llvm.objc.release(i8* %obj), !clang.imprecise_release !9
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ret void
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}
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declare void @llvm.dbg.declare(metadata, metadata, metadata)
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declare i8* @llvm.objc.retain(i8*) local_unnamed_addr
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declare void @llvm.objc.release(i8*) local_unnamed_addr
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attributes #0 = { readonly }
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!llvm.module.flags = !{!0, !1}
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!0 = !{i32 2, !"Dwarf Version", i32 4}
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!1 = !{i32 2, !"Debug Info Version", i32 3}
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!2 = !DILocalVariable(name: "i", arg: 1, scope: !3, file: !4, line: 1, type: !7)
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!3 = distinct !DISubprogram(name: "test", scope: !4, file: !4, line: 1, type: !5, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !8, retainedNodes: !9)
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!4 = !DIFile(filename: "test.m", directory: "dir")
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!5 = !DISubroutineType(types: !6)
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!6 = !{!7, !7}
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!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!8 = distinct !DICompileUnit(language: DW_LANG_ObjC, file: !4, isOptimized: false, runtimeVersion: 2, emissionKind: FullDebug, enums: !9, nameTableKind: None)
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!9 = !{}
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!10 = !DILocation(line: 1, column: 14, scope: !3)
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