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[ObjC][ARC] Delete ObjC runtime calls on global variables annotated 

with 'objc_arc_inert'

Those calls are no-ops, so they can be safely deleted.

rdar://problem/49839633

Differential Revision: https://reviews.llvm.org/D62433

llvm-svn: 363468
This commit is contained in:
Akira Hatanaka 2019-06-14 22:06:32 +00:00
parent 6cb2d9dbd2
commit a704a8f28c
4 changed files with 117 additions and 0 deletions
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4
llvm/include/llvm/Analysis/ObjCARCInstKind.h
View File

@ -74,6 +74,10 @@ bool IsForwarding(ARCInstKind Class);
/// passed a null pointer.
bool IsNoopOnNull(ARCInstKind Class);
/// Test if the given class represents instructions which do nothing if
/// passed a global variable.
bool IsNoopOnGlobal(ARCInstKind Class);
/// Test if the given class represents instructions which are always safe
/// to mark with the "tail" keyword.
bool IsAlwaysTail(ARCInstKind Class);

35
llvm/lib/Analysis/ObjCARCInstKind.cpp
View File

@ -481,6 +481,41 @@ bool llvm::objcarc::IsNoopOnNull(ARCInstKind Class) {
llvm_unreachable("covered switch isn't covered?");
}
/// Test if the given class represents instructions which do nothing if
/// passed a global variable.
bool llvm::objcarc::IsNoopOnGlobal(ARCInstKind Class) {
switch (Class) {
case ARCInstKind::Retain:
case ARCInstKind::RetainRV:
case ARCInstKind::ClaimRV:
case ARCInstKind::Release:
case ARCInstKind::Autorelease:
case ARCInstKind::AutoreleaseRV:
case ARCInstKind::RetainBlock:
case ARCInstKind::FusedRetainAutorelease:
case ARCInstKind::FusedRetainAutoreleaseRV:
return true;
case ARCInstKind::AutoreleasepoolPush:
case ARCInstKind::AutoreleasepoolPop:
case ARCInstKind::LoadWeakRetained:
case ARCInstKind::StoreWeak:
case ARCInstKind::InitWeak:
case ARCInstKind::LoadWeak:
case ARCInstKind::MoveWeak:
case ARCInstKind::CopyWeak:
case ARCInstKind::DestroyWeak:
case ARCInstKind::StoreStrong:
case ARCInstKind::IntrinsicUser:
case ARCInstKind::CallOrUser:
case ARCInstKind::Call:
case ARCInstKind::User:
case ARCInstKind::None:
case ARCInstKind::NoopCast:
return false;
}
llvm_unreachable("covered switch isn't covered?");
}
/// Test if the given class represents instructions which are always safe
/// to mark with the "tail" keyword.
bool llvm::objcarc::IsAlwaysTail(ARCInstKind Class) {

13
llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
View File

@ -760,6 +760,19 @@ void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
LLVM_DEBUG(dbgs() << "Visiting: Class: " << Class << "; " << *Inst << "\n");
// Some of the ARC calls can be deleted if their arguments are global
// variables that are inert in ARC.
if (IsNoopOnGlobal(Class)) {
Value *Opnd = Inst->getOperand(0);
if (auto *GV = dyn_cast<GlobalVariable>(Opnd->stripPointerCasts()))
if (GV->hasAttribute("objc_arc_inert")) {
if (!Inst->getType()->isVoidTy())
Inst->replaceAllUsesWith(Opnd);
Inst->eraseFromParent();
continue;
}
}
switch (Class) {
default: break;

65
llvm/test/Transforms/ObjCARC/inert-global.ll Normal file
View File

@ -0,0 +1,65 @@
; RUN: opt -objc-arc -S < %s | FileCheck %s
%0 = type opaque
%struct.__NSConstantString_tag = type { i32*, i32, i8*, i64 }
%struct.__block_descriptor = type { i64, i64 }
@__CFConstantStringClassReference = external global [0 x i32]
@.str = private unnamed_addr constant [4 x i8] c"abc\00", section "__TEXT,__cstring,cstring_literals", align 1
@.str1 = private unnamed_addr constant [4 x i8] c"def\00", section "__TEXT,__cstring,cstring_literals", align 1
@_unnamed_cfstring_ = private global %struct.__NSConstantString_tag { i32* getelementptr inbounds ([0 x i32], [0 x i32]* @__CFConstantStringClassReference, i32 0, i32 0), i32 1992, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i64 3 }, section "__DATA,__cfstring", align 8 #0
@_unnamed_cfstring_wo_attr = private global %struct.__NSConstantString_tag { i32* getelementptr inbounds ([0 x i32], [0 x i32]* @__CFConstantStringClassReference, i32 0, i32 0), i32 1992, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str1, i32 0, i32 0), i64 3 }, section "__DATA,__cfstring", align 8
@_NSConcreteGlobalBlock = external global i8*
@.str.1 = private unnamed_addr constant [6 x i8] c"v8@?0\00", align 1
@"__block_descriptor_32_e5_v8@?0l" = linkonce_odr hidden unnamed_addr constant { i64, i64, i8*, i8* } { i64 0, i64 32, i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str.1, i32 0, i32 0), i8* null }, align 8
@__block_literal_global = internal constant { i8**, i32, i32, i8*, %struct.__block_descriptor* } { i8** @_NSConcreteGlobalBlock, i32 1342177280, i32 0, i8* bitcast (void (i8*)* @__globalBlock_block_invoke to i8*), %struct.__block_descriptor* bitcast ({ i64, i64, i8*, i8* }* @"__block_descriptor_32_e5_v8@?0l" to %struct.__block_descriptor*) }, align 8 #0
; CHECK-LABEL: define %0* @stringLiteral()
; CHECK-NOT: call
; CHECK: ret %0* bitcast (%struct.__NSConstantString_tag* @_unnamed_cfstring_ to %0*)
define %0* @stringLiteral() {
%1 = tail call i8* @llvm.objc.retain(i8* bitcast (%struct.__NSConstantString_tag* @_unnamed_cfstring_ to i8*))
%2 = call i8* @llvm.objc.autorelease(i8* bitcast (%struct.__NSConstantString_tag* @_unnamed_cfstring_ to i8*))
ret %0* bitcast (%struct.__NSConstantString_tag* @_unnamed_cfstring_ to %0*)
}
; CHECK-LABEL: define %0* @stringLiteral1()
; CHECK-NEXT: call i8* @llvm.objc.retain(
; CHECK-NEXT: call i8* @llvm.objc.autorelease(
; CHECK-NEXT: ret %0*
define %0* @stringLiteral1() {
%1 = tail call i8* @llvm.objc.retain(i8* bitcast (%struct.__NSConstantString_tag* @_unnamed_cfstring_wo_attr to i8*))
%2 = call i8* @llvm.objc.autorelease(i8* bitcast (%struct.__NSConstantString_tag* @_unnamed_cfstring_wo_attr to i8*))
ret %0* bitcast (%struct.__NSConstantString_tag* @_unnamed_cfstring_wo_attr to %0*)
}
; CHECK-LABEL: define void (...)* @globalBlock()
; CHECK-NOT: call
; CHECK: %[[V1:.*]] = bitcast i8* bitcast ({ i8**, i32, i32, i8*, %struct.__block_descriptor* }* @__block_literal_global to i8*) to void (...)*
; CHECK-NEXT: ret void (...)* %[[V1]]
define void (...)* @globalBlock() {
%1 = tail call i8* @llvm.objc.retainBlock(i8* bitcast ({ i8**, i32, i32, i8*, %struct.__block_descriptor* }* @__block_literal_global to i8*))
%2 = tail call i8* @llvm.objc.retainBlock(i8* %1)
%3 = bitcast i8* %2 to void (...)*
tail call void @llvm.objc.release(i8* %1)
%4 = tail call i8* @llvm.objc.autoreleaseReturnValue(i8* %2)
ret void (...)* %3
}
define internal void @__globalBlock_block_invoke(i8* nocapture readnone) {
tail call void @foo()
ret void
}
declare void @foo()
declare i8* @llvm.objc.retain(i8*) local_unnamed_addr
declare i8* @llvm.objc.autoreleaseReturnValue(i8*) local_unnamed_addr
declare i8* @llvm.objc.retainBlock(i8*) local_unnamed_addr
declare void @llvm.objc.release(i8*) local_unnamed_addr
declare i8* @llvm.objc.autorelease(i8*) local_unnamed_addr
attributes #0 = { "objc_arc_inert" }