release/21.x [ObjCARC] Delete empty autoreleasepools with no autoreleases in them and remove ObjCARCAPElimPass #150771
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@llvm/pr-subscribers-clang @llvm/pr-subscribers-llvm-transforms Author: AZero13 (AZero13) ChangesAs per the new guidelines, I finished this with the intention of being admitted into the 21.x release. It was finished for a few weeks before it was merged, and I would like to backport this. I apolgoize if this is getting too close to the merge window, but this is just in time, no? Patch is 32.47 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/150771.diff 11 Files Affected:
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 2f6d4c414e737..17d83ff5dbebe 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1027,12 +1027,6 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
MPM.addPass(
createModuleToFunctionPassAdaptor(ObjCARCExpandPass()));
});
- PB.registerPipelineEarlySimplificationEPCallback(
- [](ModulePassManager &MPM, OptimizationLevel Level,
- ThinOrFullLTOPhase) {
- if (Level != OptimizationLevel::O0)
- MPM.addPass(ObjCARCAPElimPass());
- });
PB.registerScalarOptimizerLateEPCallback(
[](FunctionPassManager &FPM, OptimizationLevel Level) {
if (Level != OptimizationLevel::O0)
diff --git a/llvm/include/llvm/Transforms/ObjCARC.h b/llvm/include/llvm/Transforms/ObjCARC.h
index c927513469a35..c4b4c4f0b09c6 100644
--- a/llvm/include/llvm/Transforms/ObjCARC.h
+++ b/llvm/include/llvm/Transforms/ObjCARC.h
@@ -35,10 +35,6 @@ struct ObjCARCContractPass : public PassInfoMixin<ObjCARCContractPass> {
LLVM_ABI PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};
-struct ObjCARCAPElimPass : public PassInfoMixin<ObjCARCAPElimPass> {
- LLVM_ABI PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
-};
-
struct ObjCARCExpandPass : public PassInfoMixin<ObjCARCExpandPass> {
LLVM_ABI PreservedAnalyses run(Function &M, FunctionAnalysisManager &AM);
};
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
index 9a943155aa19f..8d86e2b996449 100644
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -119,7 +119,6 @@ MODULE_PASS("module-inline", ModuleInlinerPass())
MODULE_PASS("name-anon-globals", NameAnonGlobalPass())
MODULE_PASS("no-op-module", NoOpModulePass())
MODULE_PASS("nsan", NumericalStabilitySanitizerPass())
-MODULE_PASS("objc-arc-apelim", ObjCARCAPElimPass())
MODULE_PASS("openmp-opt", OpenMPOptPass())
MODULE_PASS("openmp-opt-postlink",
OpenMPOptPass(ThinOrFullLTOPhase::FullLTOPostLink))
diff --git a/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h b/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h
index 3fa844eda21cf..6135c7b938a3e 100644
--- a/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h
+++ b/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h
@@ -46,6 +46,8 @@ enum class ARCRuntimeEntryPointKind {
UnsafeClaimRV,
RetainAutorelease,
RetainAutoreleaseRV,
+ AutoreleasePoolPush,
+ AutoreleasePoolPop,
};
/// Declarations for ObjC runtime functions and constants. These are initialized
@@ -67,6 +69,8 @@ class ARCRuntimeEntryPoints {
UnsafeClaimRV = nullptr;
RetainAutorelease = nullptr;
RetainAutoreleaseRV = nullptr;
+ AutoreleasePoolPush = nullptr;
+ AutoreleasePoolPop = nullptr;
}
Function *get(ARCRuntimeEntryPointKind kind) {
@@ -101,6 +105,12 @@ class ARCRuntimeEntryPoints {
case ARCRuntimeEntryPointKind::RetainAutoreleaseRV:
return getIntrinsicEntryPoint(RetainAutoreleaseRV,
Intrinsic::objc_retainAutoreleaseReturnValue);
+ case ARCRuntimeEntryPointKind::AutoreleasePoolPush:
+ return getIntrinsicEntryPoint(AutoreleasePoolPush,
+ Intrinsic::objc_autoreleasePoolPush);
+ case ARCRuntimeEntryPointKind::AutoreleasePoolPop:
+ return getIntrinsicEntryPoint(AutoreleasePoolPop,
+ Intrinsic::objc_autoreleasePoolPop);
}
llvm_unreachable("Switch should be a covered switch.");
@@ -143,6 +153,12 @@ class ARCRuntimeEntryPoints {
/// Declaration for objc_retainAutoreleaseReturnValue().
Function *RetainAutoreleaseRV = nullptr;
+ /// Declaration for objc_autoreleasePoolPush().
+ Function *AutoreleasePoolPush = nullptr;
+
+ /// Declaration for objc_autoreleasePoolPop().
+ Function *AutoreleasePoolPop = nullptr;
+
Function *getIntrinsicEntryPoint(Function *&Decl, Intrinsic::ID IntID) {
if (Decl)
return Decl;
diff --git a/llvm/lib/Transforms/ObjCARC/CMakeLists.txt b/llvm/lib/Transforms/ObjCARC/CMakeLists.txt
index 80867dbc270d7..4274667a2c2b7 100644
--- a/llvm/lib/Transforms/ObjCARC/CMakeLists.txt
+++ b/llvm/lib/Transforms/ObjCARC/CMakeLists.txt
@@ -2,7 +2,6 @@ add_llvm_component_library(LLVMObjCARCOpts
ObjCARC.cpp
ObjCARCOpts.cpp
ObjCARCExpand.cpp
- ObjCARCAPElim.cpp
ObjCARCContract.cpp
DependencyAnalysis.cpp
ProvenanceAnalysis.cpp
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp
deleted file mode 100644
index dceb2ebb1863e..0000000000000
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp
+++ /dev/null
@@ -1,156 +0,0 @@
-//===- ObjCARCAPElim.cpp - ObjC ARC Optimization --------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-/// \file
-///
-/// This file defines ObjC ARC optimizations. ARC stands for Automatic
-/// Reference Counting and is a system for managing reference counts for objects
-/// in Objective C.
-///
-/// This specific file implements optimizations which remove extraneous
-/// autorelease pools.
-///
-/// WARNING: This file knows about certain library functions. It recognizes them
-/// by name, and hardwires knowledge of their semantics.
-///
-/// WARNING: This file knows about how certain Objective-C library functions are
-/// used. Naive LLVM IR transformations which would otherwise be
-/// behavior-preserving may break these assumptions.
-///
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/Analysis/ObjCARCAnalysisUtils.h"
-#include "llvm/Analysis/ObjCARCInstKind.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/InstrTypes.h"
-#include "llvm/IR/PassManager.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/ObjCARC.h"
-
-using namespace llvm;
-using namespace llvm::objcarc;
-
-#define DEBUG_TYPE "objc-arc-ap-elim"
-
-namespace {
-
-/// Interprocedurally determine if calls made by the given call site can
-/// possibly produce autoreleases.
-bool MayAutorelease(const CallBase &CB, unsigned Depth = 0) {
- if (const Function *Callee = CB.getCalledFunction()) {
- if (!Callee->hasExactDefinition())
- return true;
- for (const BasicBlock &BB : *Callee) {
- for (const Instruction &I : BB)
- if (const CallBase *JCB = dyn_cast<CallBase>(&I))
- // This recursion depth limit is arbitrary. It's just great
- // enough to cover known interesting testcases.
- if (Depth < 3 && !JCB->onlyReadsMemory() &&
- MayAutorelease(*JCB, Depth + 1))
- return true;
- }
- return false;
- }
-
- return true;
-}
-
-bool OptimizeBB(BasicBlock *BB) {
- bool Changed = false;
-
- Instruction *Push = nullptr;
- for (Instruction &Inst : llvm::make_early_inc_range(*BB)) {
- switch (GetBasicARCInstKind(&Inst)) {
- case ARCInstKind::AutoreleasepoolPush:
- Push = &Inst;
- break;
- case ARCInstKind::AutoreleasepoolPop:
- // If this pop matches a push and nothing in between can autorelease,
- // zap the pair.
- if (Push && cast<CallInst>(&Inst)->getArgOperand(0) == Push) {
- Changed = true;
- LLVM_DEBUG(dbgs() << "ObjCARCAPElim::OptimizeBB: Zapping push pop "
- "autorelease pair:\n"
- " Pop: "
- << Inst << "\n"
- << " Push: " << *Push
- << "\n");
- Inst.eraseFromParent();
- Push->eraseFromParent();
- }
- Push = nullptr;
- break;
- case ARCInstKind::CallOrUser:
- if (MayAutorelease(cast<CallBase>(Inst)))
- Push = nullptr;
- break;
- default:
- break;
- }
- }
-
- return Changed;
-}
-
-bool runImpl(Module &M) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!ModuleHasARC(M))
- return false;
- // Find the llvm.global_ctors variable, as the first step in
- // identifying the global constructors. In theory, unnecessary autorelease
- // pools could occur anywhere, but in practice it's pretty rare. Global
- // ctors are a place where autorelease pools get inserted automatically,
- // so it's pretty common for them to be unnecessary, and it's pretty
- // profitable to eliminate them.
- GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
- if (!GV)
- return false;
-
- assert(GV->hasDefinitiveInitializer() &&
- "llvm.global_ctors is uncooperative!");
-
- bool Changed = false;
-
- // Dig the constructor functions out of GV's initializer.
- ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
- for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
- OI != OE; ++OI) {
- Value *Op = *OI;
- // llvm.global_ctors is an array of three-field structs where the second
- // members are constructor functions.
- Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
- // If the user used a constructor function with the wrong signature and
- // it got bitcasted or whatever, look the other way.
- if (!F)
- continue;
- // Only look at function definitions.
- if (F->isDeclaration())
- continue;
- // Only look at functions with one basic block.
- if (std::next(F->begin()) != F->end())
- continue;
- // Ok, a single-block constructor function definition. Try to optimize it.
- Changed |= OptimizeBB(&F->front());
- }
-
- return Changed;
-}
-
-} // namespace
-
-PreservedAnalyses ObjCARCAPElimPass::run(Module &M, ModuleAnalysisManager &AM) {
- if (!runImpl(M))
- return PreservedAnalyses::all();
- PreservedAnalyses PA;
- PA.preserveSet<CFGAnalyses>();
- return PA;
-}
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
index 5eb3f51d38945..66a2c7632aadc 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
@@ -39,6 +39,7 @@
#include "llvm/Analysis/ObjCARCAnalysisUtils.h"
#include "llvm/Analysis/ObjCARCInstKind.h"
#include "llvm/Analysis/ObjCARCUtil.h"
+#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
@@ -132,11 +133,8 @@ static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
//
// The second retain and autorelease can be deleted.
-// TODO: It should be possible to delete
-// objc_autoreleasePoolPush and objc_autoreleasePoolPop
-// pairs if nothing is actually autoreleased between them. Also, autorelease
-// calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
-// after inlining) can be turned into plain release calls.
+// TODO: Autorelease calls followed by objc_autoreleasePoolPop calls (perhaps in
+// ObjC++ code after inlining) can be turned into plain release calls.
// TODO: Critical-edge splitting. If the optimial insertion point is
// a critical edge, the current algorithm has to fail, because it doesn't
@@ -566,6 +564,8 @@ class ObjCARCOpt {
void OptimizeReturns(Function &F);
+ void OptimizeAutoreleasePools(Function &F);
+
template <typename PredicateT>
static void cloneOpBundlesIf(CallBase *CI,
SmallVectorImpl<OperandBundleDef> &OpBundles,
@@ -2473,6 +2473,11 @@ bool ObjCARCOpt::run(Function &F, AAResults &AA) {
(1 << unsigned(ARCInstKind::AutoreleaseRV))))
OptimizeReturns(F);
+ // Optimizations for autorelease pools.
+ if (UsedInThisFunction & ((1 << unsigned(ARCInstKind::AutoreleasepoolPush)) |
+ (1 << unsigned(ARCInstKind::AutoreleasepoolPop))))
+ OptimizeAutoreleasePools(F);
+
// Gather statistics after optimization.
#ifndef NDEBUG
if (AreStatisticsEnabled()) {
@@ -2485,6 +2490,183 @@ bool ObjCARCOpt::run(Function &F, AAResults &AA) {
return Changed;
}
+/// Interprocedurally determine if calls made by the given call site can
+/// possibly produce autoreleases.
+bool MayAutorelease(const CallBase &CB, unsigned Depth = 0) {
+ if (CB.onlyReadsMemory())
+ return false;
+
+ // This recursion depth limit is arbitrary. It's just great
+ // enough to cover known interesting testcases.
+ if (Depth > 5)
+ return true;
+
+ if (const Function *Callee = CB.getCalledFunction()) {
+ if (!Callee->hasExactDefinition())
+ return true;
+ for (const BasicBlock &BB : *Callee) {
+ for (const Instruction &I : BB) {
+ // TODO: Ignore all instructions between autorelease pools
+ ARCInstKind InstKind = GetBasicARCInstKind(&I);
+ switch (InstKind) {
+ case ARCInstKind::Autorelease:
+ case ARCInstKind::AutoreleaseRV:
+ case ARCInstKind::FusedRetainAutorelease:
+ case ARCInstKind::FusedRetainAutoreleaseRV:
+ case ARCInstKind::LoadWeak:
+ // These may produce autoreleases
+ return true;
+
+ case ARCInstKind::Retain:
+ case ARCInstKind::RetainRV:
+ case ARCInstKind::UnsafeClaimRV:
+ case ARCInstKind::RetainBlock:
+ case ARCInstKind::Release:
+ case ARCInstKind::NoopCast:
+ case ARCInstKind::LoadWeakRetained:
+ case ARCInstKind::StoreWeak:
+ case ARCInstKind::InitWeak:
+ case ARCInstKind::MoveWeak:
+ case ARCInstKind::CopyWeak:
+ case ARCInstKind::DestroyWeak:
+ case ARCInstKind::StoreStrong:
+ case ARCInstKind::AutoreleasepoolPush:
+ case ARCInstKind::AutoreleasepoolPop:
+ // These ObjC runtime functions don't produce autoreleases
+ break;
+
+ case ARCInstKind::CallOrUser:
+ case ARCInstKind::Call:
+ // For non-ObjC function calls, recursively analyze
+ if (MayAutorelease(cast<CallBase>(I), Depth + 1))
+ return true;
+ break;
+
+ case ARCInstKind::IntrinsicUser:
+ case ARCInstKind::User:
+ case ARCInstKind::None:
+ // These are not relevant for autorelease analysis
+ break;
+ }
+ }
+ }
+ return false;
+ }
+
+ return true;
+}
+
+/// Optimize autorelease pools by eliminating empty push/pop pairs.
+void ObjCARCOpt::OptimizeAutoreleasePools(Function &F) {
+ LLVM_DEBUG(dbgs() << "\n== ObjCARCOpt::OptimizeAutoreleasePools ==\n");
+
+ OptimizationRemarkEmitter ORE(&F);
+
+ // Process each basic block independently.
+ // TODO: Can we optimize inter-block autorelease pool pairs?
+ // This would involve tracking autorelease pool state across blocks.
+ for (BasicBlock &BB : F) {
+ // Use a stack to track nested autorelease pools
+ SmallVector<std::pair<CallInst *, bool>, 4>
+ PoolStack; // {push_inst, has_autorelease_in_scope}
+
+ for (Instruction &Inst : llvm::make_early_inc_range(BB)) {
+ ARCInstKind Class = GetBasicARCInstKind(&Inst);
+
+ switch (Class) {
+ case ARCInstKind::AutoreleasepoolPush: {
+ // Start tracking a new autorelease pool scope
+ auto *Push = cast<CallInst>(&Inst);
+ PoolStack.push_back(
+ {Push, false}); // {push_inst, has_autorelease_in_scope}
+ LLVM_DEBUG(dbgs() << "Found autorelease pool push: " << *Push << "\n");
+ break;
+ }
+
+ case ARCInstKind::AutoreleasepoolPop: {
+ auto *Pop = cast<CallInst>(&Inst);
+
+ if (PoolStack.empty())
+ break;
+
+ auto &TopPool = PoolStack.back();
+ CallInst *PendingPush = TopPool.first;
+ bool HasAutoreleaseInScope = TopPool.second;
+
+ // Pop the stack - remove this pool scope
+ PoolStack.pop_back();
+
+ // Bail if this pop doesn't match the pending push
+ if (Pop->getArgOperand(0)->stripPointerCasts() != PendingPush)
+ break;
+
+ // Bail if there were autoreleases in this scope
+ if (HasAutoreleaseInScope)
+ break;
+
+ // Optimize: eliminate this empty autorelease pool pair
+ ORE.emit([&]() {
+ return OptimizationRemark(DEBUG_TYPE, "AutoreleasePoolElimination",
+ PendingPush)
+ << "eliminated empty autorelease pool pair";
+ });
+
+ // Replace all uses of push with poison before deletion
+ PendingPush->replaceAllUsesWith(
+ PoisonValue::get(PendingPush->getType()));
+
+ Pop->eraseFromParent();
+ PendingPush->eraseFromParent();
+
+ Changed = true;
+ ++NumNoops;
+ break;
+ }
+ case ARCInstKind::CallOrUser:
+ case ARCInstKind::Call:
+ if (!MayAutorelease(cast<CallBase>(Inst)))
+ break;
+ LLVM_FALLTHROUGH;
+ case ARCInstKind::Autorelease:
+ case ARCInstKind::AutoreleaseRV:
+ case ARCInstKind::FusedRetainAutorelease:
+ case ARCInstKind::FusedRetainAutoreleaseRV:
+ case ARCInstKind::LoadWeak: {
+ // Track that we have autorelease calls in the current pool scope
+ if (!PoolStack.empty()) {
+ PoolStack.back().second = true; // Set has_autorelease_in_scope = true
+ LLVM_DEBUG(
+ dbgs()
+ << "Found autorelease or potential autorelease in pool scope: "
+ << Inst << "\n");
+ }
+ break;
+ }
+
+ // Enumerate all remaining ARCInstKind cases explicitly
+ case ARCInstKind::Retain:
+ case ARCInstKind::RetainRV:
+ case ARCInstKind::UnsafeClaimRV:
+ case ARCInstKind::RetainBlock:
+ case ARCInstKind::Release:
+ case ARCInstKind::NoopCast:
+ case ARCInstKind::LoadWeakRetained:
+ case ARCInstKind::StoreWeak:
+ case ARCInstKind::InitWeak:
+ case ARCInstKind::MoveWeak:
+ case ARCInstKind::CopyWeak:
+ case ARCInstKind::DestroyWeak:
+ case ARCInstKind::StoreStrong:
+ case ARCInstKind::IntrinsicUser:
+ case ARCInstKind::User:
+ case ARCInstKind::None:
+ // These instruction kinds don't affect autorelease pool optimization
+ break;
+ }
+ }
+ }
+}
+
/// @}
///
diff --git a/llvm/test/Transforms/ObjCARC/apelim.ll b/llvm/test/Transforms/ObjCARC/apelim.ll
index 2ac5d15d0df85..01179f3dec048 100644
--- a/llvm/test/Transforms/ObjCARC/apelim.ll
+++ b/llvm/test/Transforms/ObjCARC/apelim.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -passes=objc-arc-apelim < %s | FileCheck %s
+; RUN: opt -S -passes=objc-arc < %s | FileCheck %s
; rdar://10227311
@llvm.global_ctors = appending global [2 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 65535, ptr @_GLOBAL__I_x, ptr null }, { i32, ptr, ptr } { i32 65535, ptr @_GLOBAL__I_y, ptr null }]
diff --git a/llvm/test/Transforms/ObjCARC/comdat-ipo.ll b/llvm/test/Transforms/ObjCARC/comdat-ipo.ll
index 3f91d3bea9f14..d43804c20d936 100644
--- a/llvm/test/Transforms/ObjCARC/comdat-ipo.ll
+++ b/llvm/test/Transforms/ObjCARC/comdat-ipo.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -passes=objc-arc-apelim < %s | FileCheck %s
+; RUN: opt -S -passes=objc-arc < %s | FileCheck %s
; See PR26774
diff --git a/llvm/test/Transforms/ObjCARC/test_autorelease_pool.ll b/llvm/test/Transforms/ObjCARC/test_autorelease_pool.ll
new file mode 100644
index 0000000000000..896717f92146f
--- /dev/null
+++ b/llvm/test/Transforms/ObjCARC/test_autorelease_pool.ll
@@ -0,0 +1,319 @@
+; 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()
+declare void @opaque_callee()
+
+; Empty autorelease pool should be eliminated
+define void @test_empty_pool() {
+; CHECK-LABEL: define void @test_empty_pool() {
+; C...
[truncated]
|
|
@llvm/pr-subscribers-clang-codegen Author: AZero13 (AZero13) ChangesAs per the new guidelines, I finished this with the intention of being admitted into the 21.x release. It was finished for a few weeks before it was merged, and I would like to backport this. I apolgoize if this is getting too close to the merge window, but this is just in time, no? Patch is 32.47 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/150771.diff 11 Files Affected:
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 2f6d4c414e737..17d83ff5dbebe 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1027,12 +1027,6 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
MPM.addPass(
createModuleToFunctionPassAdaptor(ObjCARCExpandPass()));
});
- PB.registerPipelineEarlySimplificationEPCallback(
- [](ModulePassManager &MPM, OptimizationLevel Level,
- ThinOrFullLTOPhase) {
- if (Level != OptimizationLevel::O0)
- MPM.addPass(ObjCARCAPElimPass());
- });
PB.registerScalarOptimizerLateEPCallback(
[](FunctionPassManager &FPM, OptimizationLevel Level) {
if (Level != OptimizationLevel::O0)
diff --git a/llvm/include/llvm/Transforms/ObjCARC.h b/llvm/include/llvm/Transforms/ObjCARC.h
index c927513469a35..c4b4c4f0b09c6 100644
--- a/llvm/include/llvm/Transforms/ObjCARC.h
+++ b/llvm/include/llvm/Transforms/ObjCARC.h
@@ -35,10 +35,6 @@ struct ObjCARCContractPass : public PassInfoMixin<ObjCARCContractPass> {
LLVM_ABI PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};
-struct ObjCARCAPElimPass : public PassInfoMixin<ObjCARCAPElimPass> {
- LLVM_ABI PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
-};
-
struct ObjCARCExpandPass : public PassInfoMixin<ObjCARCExpandPass> {
LLVM_ABI PreservedAnalyses run(Function &M, FunctionAnalysisManager &AM);
};
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
index 9a943155aa19f..8d86e2b996449 100644
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -119,7 +119,6 @@ MODULE_PASS("module-inline", ModuleInlinerPass())
MODULE_PASS("name-anon-globals", NameAnonGlobalPass())
MODULE_PASS("no-op-module", NoOpModulePass())
MODULE_PASS("nsan", NumericalStabilitySanitizerPass())
-MODULE_PASS("objc-arc-apelim", ObjCARCAPElimPass())
MODULE_PASS("openmp-opt", OpenMPOptPass())
MODULE_PASS("openmp-opt-postlink",
OpenMPOptPass(ThinOrFullLTOPhase::FullLTOPostLink))
diff --git a/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h b/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h
index 3fa844eda21cf..6135c7b938a3e 100644
--- a/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h
+++ b/llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h
@@ -46,6 +46,8 @@ enum class ARCRuntimeEntryPointKind {
UnsafeClaimRV,
RetainAutorelease,
RetainAutoreleaseRV,
+ AutoreleasePoolPush,
+ AutoreleasePoolPop,
};
/// Declarations for ObjC runtime functions and constants. These are initialized
@@ -67,6 +69,8 @@ class ARCRuntimeEntryPoints {
UnsafeClaimRV = nullptr;
RetainAutorelease = nullptr;
RetainAutoreleaseRV = nullptr;
+ AutoreleasePoolPush = nullptr;
+ AutoreleasePoolPop = nullptr;
}
Function *get(ARCRuntimeEntryPointKind kind) {
@@ -101,6 +105,12 @@ class ARCRuntimeEntryPoints {
case ARCRuntimeEntryPointKind::RetainAutoreleaseRV:
return getIntrinsicEntryPoint(RetainAutoreleaseRV,
Intrinsic::objc_retainAutoreleaseReturnValue);
+ case ARCRuntimeEntryPointKind::AutoreleasePoolPush:
+ return getIntrinsicEntryPoint(AutoreleasePoolPush,
+ Intrinsic::objc_autoreleasePoolPush);
+ case ARCRuntimeEntryPointKind::AutoreleasePoolPop:
+ return getIntrinsicEntryPoint(AutoreleasePoolPop,
+ Intrinsic::objc_autoreleasePoolPop);
}
llvm_unreachable("Switch should be a covered switch.");
@@ -143,6 +153,12 @@ class ARCRuntimeEntryPoints {
/// Declaration for objc_retainAutoreleaseReturnValue().
Function *RetainAutoreleaseRV = nullptr;
+ /// Declaration for objc_autoreleasePoolPush().
+ Function *AutoreleasePoolPush = nullptr;
+
+ /// Declaration for objc_autoreleasePoolPop().
+ Function *AutoreleasePoolPop = nullptr;
+
Function *getIntrinsicEntryPoint(Function *&Decl, Intrinsic::ID IntID) {
if (Decl)
return Decl;
diff --git a/llvm/lib/Transforms/ObjCARC/CMakeLists.txt b/llvm/lib/Transforms/ObjCARC/CMakeLists.txt
index 80867dbc270d7..4274667a2c2b7 100644
--- a/llvm/lib/Transforms/ObjCARC/CMakeLists.txt
+++ b/llvm/lib/Transforms/ObjCARC/CMakeLists.txt
@@ -2,7 +2,6 @@ add_llvm_component_library(LLVMObjCARCOpts
ObjCARC.cpp
ObjCARCOpts.cpp
ObjCARCExpand.cpp
- ObjCARCAPElim.cpp
ObjCARCContract.cpp
DependencyAnalysis.cpp
ProvenanceAnalysis.cpp
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp
deleted file mode 100644
index dceb2ebb1863e..0000000000000
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp
+++ /dev/null
@@ -1,156 +0,0 @@
-//===- ObjCARCAPElim.cpp - ObjC ARC Optimization --------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-/// \file
-///
-/// This file defines ObjC ARC optimizations. ARC stands for Automatic
-/// Reference Counting and is a system for managing reference counts for objects
-/// in Objective C.
-///
-/// This specific file implements optimizations which remove extraneous
-/// autorelease pools.
-///
-/// WARNING: This file knows about certain library functions. It recognizes them
-/// by name, and hardwires knowledge of their semantics.
-///
-/// WARNING: This file knows about how certain Objective-C library functions are
-/// used. Naive LLVM IR transformations which would otherwise be
-/// behavior-preserving may break these assumptions.
-///
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/Analysis/ObjCARCAnalysisUtils.h"
-#include "llvm/Analysis/ObjCARCInstKind.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/InstrTypes.h"
-#include "llvm/IR/PassManager.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/ObjCARC.h"
-
-using namespace llvm;
-using namespace llvm::objcarc;
-
-#define DEBUG_TYPE "objc-arc-ap-elim"
-
-namespace {
-
-/// Interprocedurally determine if calls made by the given call site can
-/// possibly produce autoreleases.
-bool MayAutorelease(const CallBase &CB, unsigned Depth = 0) {
- if (const Function *Callee = CB.getCalledFunction()) {
- if (!Callee->hasExactDefinition())
- return true;
- for (const BasicBlock &BB : *Callee) {
- for (const Instruction &I : BB)
- if (const CallBase *JCB = dyn_cast<CallBase>(&I))
- // This recursion depth limit is arbitrary. It's just great
- // enough to cover known interesting testcases.
- if (Depth < 3 && !JCB->onlyReadsMemory() &&
- MayAutorelease(*JCB, Depth + 1))
- return true;
- }
- return false;
- }
-
- return true;
-}
-
-bool OptimizeBB(BasicBlock *BB) {
- bool Changed = false;
-
- Instruction *Push = nullptr;
- for (Instruction &Inst : llvm::make_early_inc_range(*BB)) {
- switch (GetBasicARCInstKind(&Inst)) {
- case ARCInstKind::AutoreleasepoolPush:
- Push = &Inst;
- break;
- case ARCInstKind::AutoreleasepoolPop:
- // If this pop matches a push and nothing in between can autorelease,
- // zap the pair.
- if (Push && cast<CallInst>(&Inst)->getArgOperand(0) == Push) {
- Changed = true;
- LLVM_DEBUG(dbgs() << "ObjCARCAPElim::OptimizeBB: Zapping push pop "
- "autorelease pair:\n"
- " Pop: "
- << Inst << "\n"
- << " Push: " << *Push
- << "\n");
- Inst.eraseFromParent();
- Push->eraseFromParent();
- }
- Push = nullptr;
- break;
- case ARCInstKind::CallOrUser:
- if (MayAutorelease(cast<CallBase>(Inst)))
- Push = nullptr;
- break;
- default:
- break;
- }
- }
-
- return Changed;
-}
-
-bool runImpl(Module &M) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!ModuleHasARC(M))
- return false;
- // Find the llvm.global_ctors variable, as the first step in
- // identifying the global constructors. In theory, unnecessary autorelease
- // pools could occur anywhere, but in practice it's pretty rare. Global
- // ctors are a place where autorelease pools get inserted automatically,
- // so it's pretty common for them to be unnecessary, and it's pretty
- // profitable to eliminate them.
- GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
- if (!GV)
- return false;
-
- assert(GV->hasDefinitiveInitializer() &&
- "llvm.global_ctors is uncooperative!");
-
- bool Changed = false;
-
- // Dig the constructor functions out of GV's initializer.
- ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
- for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
- OI != OE; ++OI) {
- Value *Op = *OI;
- // llvm.global_ctors is an array of three-field structs where the second
- // members are constructor functions.
- Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
- // If the user used a constructor function with the wrong signature and
- // it got bitcasted or whatever, look the other way.
- if (!F)
- continue;
- // Only look at function definitions.
- if (F->isDeclaration())
- continue;
- // Only look at functions with one basic block.
- if (std::next(F->begin()) != F->end())
- continue;
- // Ok, a single-block constructor function definition. Try to optimize it.
- Changed |= OptimizeBB(&F->front());
- }
-
- return Changed;
-}
-
-} // namespace
-
-PreservedAnalyses ObjCARCAPElimPass::run(Module &M, ModuleAnalysisManager &AM) {
- if (!runImpl(M))
- return PreservedAnalyses::all();
- PreservedAnalyses PA;
- PA.preserveSet<CFGAnalyses>();
- return PA;
-}
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
index 5eb3f51d38945..66a2c7632aadc 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
@@ -39,6 +39,7 @@
#include "llvm/Analysis/ObjCARCAnalysisUtils.h"
#include "llvm/Analysis/ObjCARCInstKind.h"
#include "llvm/Analysis/ObjCARCUtil.h"
+#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
@@ -132,11 +133,8 @@ static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
//
// The second retain and autorelease can be deleted.
-// TODO: It should be possible to delete
-// objc_autoreleasePoolPush and objc_autoreleasePoolPop
-// pairs if nothing is actually autoreleased between them. Also, autorelease
-// calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
-// after inlining) can be turned into plain release calls.
+// TODO: Autorelease calls followed by objc_autoreleasePoolPop calls (perhaps in
+// ObjC++ code after inlining) can be turned into plain release calls.
// TODO: Critical-edge splitting. If the optimial insertion point is
// a critical edge, the current algorithm has to fail, because it doesn't
@@ -566,6 +564,8 @@ class ObjCARCOpt {
void OptimizeReturns(Function &F);
+ void OptimizeAutoreleasePools(Function &F);
+
template <typename PredicateT>
static void cloneOpBundlesIf(CallBase *CI,
SmallVectorImpl<OperandBundleDef> &OpBundles,
@@ -2473,6 +2473,11 @@ bool ObjCARCOpt::run(Function &F, AAResults &AA) {
(1 << unsigned(ARCInstKind::AutoreleaseRV))))
OptimizeReturns(F);
+ // Optimizations for autorelease pools.
+ if (UsedInThisFunction & ((1 << unsigned(ARCInstKind::AutoreleasepoolPush)) |
+ (1 << unsigned(ARCInstKind::AutoreleasepoolPop))))
+ OptimizeAutoreleasePools(F);
+
// Gather statistics after optimization.
#ifndef NDEBUG
if (AreStatisticsEnabled()) {
@@ -2485,6 +2490,183 @@ bool ObjCARCOpt::run(Function &F, AAResults &AA) {
return Changed;
}
+/// Interprocedurally determine if calls made by the given call site can
+/// possibly produce autoreleases.
+bool MayAutorelease(const CallBase &CB, unsigned Depth = 0) {
+ if (CB.onlyReadsMemory())
+ return false;
+
+ // This recursion depth limit is arbitrary. It's just great
+ // enough to cover known interesting testcases.
+ if (Depth > 5)
+ return true;
+
+ if (const Function *Callee = CB.getCalledFunction()) {
+ if (!Callee->hasExactDefinition())
+ return true;
+ for (const BasicBlock &BB : *Callee) {
+ for (const Instruction &I : BB) {
+ // TODO: Ignore all instructions between autorelease pools
+ ARCInstKind InstKind = GetBasicARCInstKind(&I);
+ switch (InstKind) {
+ case ARCInstKind::Autorelease:
+ case ARCInstKind::AutoreleaseRV:
+ case ARCInstKind::FusedRetainAutorelease:
+ case ARCInstKind::FusedRetainAutoreleaseRV:
+ case ARCInstKind::LoadWeak:
+ // These may produce autoreleases
+ return true;
+
+ case ARCInstKind::Retain:
+ case ARCInstKind::RetainRV:
+ case ARCInstKind::UnsafeClaimRV:
+ case ARCInstKind::RetainBlock:
+ case ARCInstKind::Release:
+ case ARCInstKind::NoopCast:
+ case ARCInstKind::LoadWeakRetained:
+ case ARCInstKind::StoreWeak:
+ case ARCInstKind::InitWeak:
+ case ARCInstKind::MoveWeak:
+ case ARCInstKind::CopyWeak:
+ case ARCInstKind::DestroyWeak:
+ case ARCInstKind::StoreStrong:
+ case ARCInstKind::AutoreleasepoolPush:
+ case ARCInstKind::AutoreleasepoolPop:
+ // These ObjC runtime functions don't produce autoreleases
+ break;
+
+ case ARCInstKind::CallOrUser:
+ case ARCInstKind::Call:
+ // For non-ObjC function calls, recursively analyze
+ if (MayAutorelease(cast<CallBase>(I), Depth + 1))
+ return true;
+ break;
+
+ case ARCInstKind::IntrinsicUser:
+ case ARCInstKind::User:
+ case ARCInstKind::None:
+ // These are not relevant for autorelease analysis
+ break;
+ }
+ }
+ }
+ return false;
+ }
+
+ return true;
+}
+
+/// Optimize autorelease pools by eliminating empty push/pop pairs.
+void ObjCARCOpt::OptimizeAutoreleasePools(Function &F) {
+ LLVM_DEBUG(dbgs() << "\n== ObjCARCOpt::OptimizeAutoreleasePools ==\n");
+
+ OptimizationRemarkEmitter ORE(&F);
+
+ // Process each basic block independently.
+ // TODO: Can we optimize inter-block autorelease pool pairs?
+ // This would involve tracking autorelease pool state across blocks.
+ for (BasicBlock &BB : F) {
+ // Use a stack to track nested autorelease pools
+ SmallVector<std::pair<CallInst *, bool>, 4>
+ PoolStack; // {push_inst, has_autorelease_in_scope}
+
+ for (Instruction &Inst : llvm::make_early_inc_range(BB)) {
+ ARCInstKind Class = GetBasicARCInstKind(&Inst);
+
+ switch (Class) {
+ case ARCInstKind::AutoreleasepoolPush: {
+ // Start tracking a new autorelease pool scope
+ auto *Push = cast<CallInst>(&Inst);
+ PoolStack.push_back(
+ {Push, false}); // {push_inst, has_autorelease_in_scope}
+ LLVM_DEBUG(dbgs() << "Found autorelease pool push: " << *Push << "\n");
+ break;
+ }
+
+ case ARCInstKind::AutoreleasepoolPop: {
+ auto *Pop = cast<CallInst>(&Inst);
+
+ if (PoolStack.empty())
+ break;
+
+ auto &TopPool = PoolStack.back();
+ CallInst *PendingPush = TopPool.first;
+ bool HasAutoreleaseInScope = TopPool.second;
+
+ // Pop the stack - remove this pool scope
+ PoolStack.pop_back();
+
+ // Bail if this pop doesn't match the pending push
+ if (Pop->getArgOperand(0)->stripPointerCasts() != PendingPush)
+ break;
+
+ // Bail if there were autoreleases in this scope
+ if (HasAutoreleaseInScope)
+ break;
+
+ // Optimize: eliminate this empty autorelease pool pair
+ ORE.emit([&]() {
+ return OptimizationRemark(DEBUG_TYPE, "AutoreleasePoolElimination",
+ PendingPush)
+ << "eliminated empty autorelease pool pair";
+ });
+
+ // Replace all uses of push with poison before deletion
+ PendingPush->replaceAllUsesWith(
+ PoisonValue::get(PendingPush->getType()));
+
+ Pop->eraseFromParent();
+ PendingPush->eraseFromParent();
+
+ Changed = true;
+ ++NumNoops;
+ break;
+ }
+ case ARCInstKind::CallOrUser:
+ case ARCInstKind::Call:
+ if (!MayAutorelease(cast<CallBase>(Inst)))
+ break;
+ LLVM_FALLTHROUGH;
+ case ARCInstKind::Autorelease:
+ case ARCInstKind::AutoreleaseRV:
+ case ARCInstKind::FusedRetainAutorelease:
+ case ARCInstKind::FusedRetainAutoreleaseRV:
+ case ARCInstKind::LoadWeak: {
+ // Track that we have autorelease calls in the current pool scope
+ if (!PoolStack.empty()) {
+ PoolStack.back().second = true; // Set has_autorelease_in_scope = true
+ LLVM_DEBUG(
+ dbgs()
+ << "Found autorelease or potential autorelease in pool scope: "
+ << Inst << "\n");
+ }
+ break;
+ }
+
+ // Enumerate all remaining ARCInstKind cases explicitly
+ case ARCInstKind::Retain:
+ case ARCInstKind::RetainRV:
+ case ARCInstKind::UnsafeClaimRV:
+ case ARCInstKind::RetainBlock:
+ case ARCInstKind::Release:
+ case ARCInstKind::NoopCast:
+ case ARCInstKind::LoadWeakRetained:
+ case ARCInstKind::StoreWeak:
+ case ARCInstKind::InitWeak:
+ case ARCInstKind::MoveWeak:
+ case ARCInstKind::CopyWeak:
+ case ARCInstKind::DestroyWeak:
+ case ARCInstKind::StoreStrong:
+ case ARCInstKind::IntrinsicUser:
+ case ARCInstKind::User:
+ case ARCInstKind::None:
+ // These instruction kinds don't affect autorelease pool optimization
+ break;
+ }
+ }
+ }
+}
+
/// @}
///
diff --git a/llvm/test/Transforms/ObjCARC/apelim.ll b/llvm/test/Transforms/ObjCARC/apelim.ll
index 2ac5d15d0df85..01179f3dec048 100644
--- a/llvm/test/Transforms/ObjCARC/apelim.ll
+++ b/llvm/test/Transforms/ObjCARC/apelim.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -passes=objc-arc-apelim < %s | FileCheck %s
+; RUN: opt -S -passes=objc-arc < %s | FileCheck %s
; rdar://10227311
@llvm.global_ctors = appending global [2 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 65535, ptr @_GLOBAL__I_x, ptr null }, { i32, ptr, ptr } { i32 65535, ptr @_GLOBAL__I_y, ptr null }]
diff --git a/llvm/test/Transforms/ObjCARC/comdat-ipo.ll b/llvm/test/Transforms/ObjCARC/comdat-ipo.ll
index 3f91d3bea9f14..d43804c20d936 100644
--- a/llvm/test/Transforms/ObjCARC/comdat-ipo.ll
+++ b/llvm/test/Transforms/ObjCARC/comdat-ipo.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -passes=objc-arc-apelim < %s | FileCheck %s
+; RUN: opt -S -passes=objc-arc < %s | FileCheck %s
; See PR26774
diff --git a/llvm/test/Transforms/ObjCARC/test_autorelease_pool.ll b/llvm/test/Transforms/ObjCARC/test_autorelease_pool.ll
new file mode 100644
index 0000000000000..896717f92146f
--- /dev/null
+++ b/llvm/test/Transforms/ObjCARC/test_autorelease_pool.ll
@@ -0,0 +1,319 @@
+; 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()
+declare void @opaque_callee()
+
+; Empty autorelease pool should be eliminated
+define void @test_empty_pool() {
+; CHECK-LABEL: define void @test_empty_pool() {
+; C...
[truncated]
|
nikic
requested changes
Jul 26, 2025
|
I would most likely defer to @nikic here, but can you give us a good case for merging this into the release? |
A few reasons:
|
…lvm#144788) Erase empty autorelease pools that have no autorelease in them
ObjCARCAPElimPass has been made obsolete now that we remove unused autorelease pools.
|
@nikic What do you think? do you have strong feelings about merging this, I would normally agree with you, but since we moved the date forward and it's still early in the release process I don't mind as much. |
|
Yes, I feel strongly that this should not be backported. This patch is both unimportant and risky. |
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As per the new guidelines, I finished this with the intention of being admitted into the 21.x release.
It was finished for a few weeks before it was merged, and I would like to backport this. I apolgoize if this is getting too close to the merge window, but this is just in time, no?