pete updated this revision to Diff 50651.
pete added a comment.
Thanks for the example John. I understand what you mean now.
I've added this piece to the test case which verifies that the following IR has
the correct bit cast in it. Similarly added cases for alloc and autorelease.
@class A;
@interface B
- (A*) retain;
@end
A* test_retain_class_ptr(B *b) {
return [b retain];
}
define %1* @test_retain_class_ptr(%2* %b) #0 {
entry:
%b.addr = alloca %2*, align 8
store %2* %b, %2** %b.addr, align 8
%0 = load %2*, %2** %b.addr, align 8
%1 = bitcast %2* %0 to i8*
%2 = call i8* @objc_retain(i8* %1) #2
%3 = bitcast i8* %2 to %1*
ret %1* %3
}
http://reviews.llvm.org/D14737
Files:
include/clang/Basic/ObjCRuntime.h
include/clang/Driver/Options.td
include/clang/Frontend/CodeGenOptions.def
lib/CodeGen/CGObjC.cpp
lib/CodeGen/CodeGenFunction.h
lib/CodeGen/CodeGenModule.h
lib/Driver/Tools.cpp
lib/Frontend/CompilerInvocation.cpp
test/CodeGenObjC/convert-messages-to-runtime-calls.m
test/Driver/objc-convert-messages-to-runtime-calls.m
Index: test/Driver/objc-convert-messages-to-runtime-calls.m
===================================================================
--- /dev/null
+++ test/Driver/objc-convert-messages-to-runtime-calls.m
@@ -0,0 +1,7 @@
+// RUN: %clang %s -### -o %t.o 2>&1 -fsyntax-only -fobjc-convert-messages-to-runtime-calls -fno-objc-convert-messages-to-runtime-calls -target x86_64-apple-macosx10.10.0 | FileCheck %s --check-prefix=DISABLE
+// RUN: %clang %s -### -o %t.o 2>&1 -fsyntax-only -fno-objc-convert-messages-to-runtime-calls -fobjc-convert-messages-to-runtime-calls -target x86_64-apple-macosx10.10.0 | FileCheck %s --check-prefix=ENABLE
+
+// Check that we pass fobjc-convert-messages-to-runtime-calls only when supported, and not explicitly disabled.
+
+// DISABLE: "-fno-objc-convert-messages-to-runtime-calls"
+// ENABLE-NOT: "-fno-objc-convert-messages-to-runtime-calls"
Index: test/CodeGenObjC/convert-messages-to-runtime-calls.m
===================================================================
--- /dev/null
+++ test/CodeGenObjC/convert-messages-to-runtime-calls.m
@@ -0,0 +1,129 @@
+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.10.0 -emit-llvm -o - %s -fno-objc-convert-messages-to-runtime-calls | FileCheck %s --check-prefix=MSGS
+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.10.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.9.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=MSGS
+// RUN: %clang_cc1 -fobjc-runtime=macosx-fragile-10.10.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=MSGS
+// Make sure we don't do calls to retain/release when using GC.
+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.10.0 -emit-llvm -o - %s -fobjc-gc | FileCheck %s --check-prefix=GC
+// RUN: %clang_cc1 -fobjc-runtime=ios-8.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+// RUN: %clang_cc1 -fobjc-runtime=ios-7.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=MSGS
+// Note: This line below is for tvos for which the driver passes through to use the ios9.0 runtime.
+// RUN: %clang_cc1 -fobjc-runtime=ios-9.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+// RUN: %clang_cc1 -fobjc-runtime=watchos-2.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+
+@interface NSObject
++ (id)alloc;
++ (id)alloc2;
+- (id)init;
+- (id)retain;
+- (void)release;
+- (id)autorelease;
+@end
+
+@interface NSString : NSObject
++ (void)retain_self;
+- (void)retain_super;
+@end
+
+// CHECK-LABEL: define {{.*}}void @test1
+void test1(id x) {
+ // MSGS: {{call.*@objc_msgSend}}
+ // MSGS: {{call.*@objc_msgSend}}
+ // MSGS: {{call.*@objc_msgSend}}
+ // MSGS: {{call.*@objc_msgSend}}
+ // CALLS: {{call.*@objc_alloc}}
+ // CALLS: {{call.*@objc_retain}}
+ // CALLS: {{call.*@objc_release}}
+ // CALLS: {{call.*@objc_autorelease}}
+ // GC: {{call.*@objc_alloc}}
+ // GC: {{call.*@objc_msgSend}}
+ // GC: {{call.*@objc_msgSend}}
+ // GC: {{call.*@objc_msgSend}}
+ [NSObject alloc];
+ [x retain];
+ [x release];
+ [x autorelease];
+}
+
+// CHECK-LABEL: define {{.*}}void @test2
+void test2() {
+ // MSGS: {{call.*@objc_msgSend}}
+ // CALLS: {{call.*@objc_msgSend}}
+ // GC: {{call.*@objc_msgSend}}
+ // Make sure alloc has the correct name and number of types.
+ [NSObject alloc2];
+}
+
+@class A;
+@interface B
++ (A*) alloc;
+- (A*) retain;
+- (A*) autorelease;
+@end
+
+// Make sure we get a bitcast on the return type as the
+// call will return i8* which we have to cast to A*
+// CHECK-LABEL: define {{.*}}void @test_alloc_class_ptr
+A* test_alloc_class_ptr() {
+ // CALLS: {{call.*@objc_alloc}}
+ // CALLS-NEXT: bitcast i8*
+ // CALLS-NEXT: ret
+ return [B alloc];
+}
+
+// Make sure we get a bitcast on the return type as the
+// call will return i8* which we have to cast to A*
+// CHECK-LABEL: define {{.*}}void @test_retain_class_ptr
+A* test_retain_class_ptr(B *b) {
+ // CALLS: {{call.*@objc_retain}}
+ // CALLS-NEXT: bitcast i8*
+ // CALLS-NEXT: ret
+ return [b retain];
+}
+
+// Make sure we get a bitcast on the return type as the
+// call will return i8* which we have to cast to A*
+// CHECK-LABEL: define {{.*}}void @test_autorelease_class_ptr
+A* test_autorelease_class_ptr(B *b) {
+ // CALLS: {{call.*@objc_autorelease}}
+ // CALLS-NEXT: bitcast i8*
+ // CALLS-NEXT: ret
+ return [b autorelease];
+}
+
+@interface C
+- (float) retain;
+@end
+
+// Make sure we use a message and not a call as the return type is
+// not a pointer type.
+// CHECK-LABEL: define {{.*}}void @test_cannot_message_return_float
+float test_cannot_message_return_float(C *c) {
+ // MSGS: {{call.*@objc_msgSend}}
+ // CALLS: {{call.*@objc_msgSend}}
+ // GC: {{call.*@objc_msgSend}}
+ return [c retain];
+}
+
+@implementation NSString
+
+// Make sure we can convert a message to a dynamic receiver to a call
+// CHECK-LABEL: define {{.*}}void @retain_self
++ (void)retain_self {
+ // MSGS: {{call.*@objc_msgSend}}
+ // CALLS: {{call.*@objc_retain}}
+ // GC: {{call.*@objc_msgSend}}
+ [self retain];
+}
+
+// Make sure we never convert a message to super to a call
+// CHECK-LABEL: define {{.*}}void @retain_super
+- (void)retain_super {
+ // MSGS: {{call.*@objc_msgSend}}
+ // CALLS: {{call.*@objc_msgSend}}
+ // GC: {{call.*@objc_msgSend}}
+ [super retain];
+}
+
+@end
+
+
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -706,6 +706,9 @@
}
}
+ if (Args.hasArg(OPT_fno_objc_convert_messages_to_runtime_calls))
+ Opts.ObjCConvertMessagesToRuntimeCalls = 0;
+
Opts.EmulatedTLS =
Args.hasFlag(OPT_femulated_tls, OPT_fno_emulated_tls, false);
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -5282,6 +5282,18 @@
}
+ // Allow the user to control whether messages can be converted to runtime
+ // functions.
+ if (types::isObjC(InputType)) {
+ auto *Arg = Args.getLastArg(
+ options::OPT_fobjc_convert_messages_to_runtime_calls,
+ options::OPT_fno_objc_convert_messages_to_runtime_calls);
+ if (Arg &&
+ Arg->getOption().matches(
+ options::OPT_fno_objc_convert_messages_to_runtime_calls))
+ CmdArgs.push_back("-fno-objc-convert-messages-to-runtime-calls");
+ }
+
// -fobjc-infer-related-result-type is the default, except in the Objective-C
// rewriter.
if (rewriteKind != RK_None)
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -113,7 +113,10 @@
struct ObjCEntrypoints {
ObjCEntrypoints() { memset(this, 0, sizeof(*this)); }
- /// void objc_autoreleasePoolPop(void*);
+ /// void objc_alloc(id);
+ llvm::Constant *objc_alloc;
+
+ /// void objc_autoreleasePoolPop(void*);
llvm::Constant *objc_autoreleasePoolPop;
/// void *objc_autoreleasePoolPush(void);
Index: lib/CodeGen/CodeGenFunction.h
===================================================================
--- lib/CodeGen/CodeGenFunction.h
+++ lib/CodeGen/CodeGenFunction.h
@@ -2821,11 +2821,13 @@
llvm::Value *EmitARCStoreStrongCall(Address addr, llvm::Value *value,
bool resultIgnored);
llvm::Value *EmitARCRetain(QualType type, llvm::Value *value);
- llvm::Value *EmitARCRetainNonBlock(llvm::Value *value);
+ llvm::Value *EmitARCRetainNonBlock(llvm::Value *value,
+ llvm::Type *returnType = nullptr);
llvm::Value *EmitARCRetainBlock(llvm::Value *value, bool mandatory);
void EmitARCDestroyStrong(Address addr, ARCPreciseLifetime_t precise);
void EmitARCRelease(llvm::Value *value, ARCPreciseLifetime_t precise);
- llvm::Value *EmitARCAutorelease(llvm::Value *value);
+ llvm::Value *EmitARCAutorelease(llvm::Value *value,
+ llvm::Type *returnType = nullptr);
llvm::Value *EmitARCAutoreleaseReturnValue(llvm::Value *value);
llvm::Value *EmitARCRetainAutoreleaseReturnValue(llvm::Value *value);
llvm::Value *EmitARCRetainAutoreleasedReturnValue(llvm::Value *value);
@@ -2838,6 +2840,8 @@
std::pair<LValue,llvm::Value*>
EmitARCStoreUnsafeUnretained(const BinaryOperator *e, bool ignored);
+ llvm::Value *EmitObjCAlloc(llvm::Value *value,
+ llvm::Type *returnType = nullptr);
llvm::Value *EmitObjCThrowOperand(const Expr *expr);
llvm::Value *EmitObjCConsumeObject(QualType T, llvm::Value *Ptr);
llvm::Value *EmitObjCExtendObjectLifetime(QualType T, llvm::Value *Ptr);
Index: lib/CodeGen/CGObjC.cpp
===================================================================
--- lib/CodeGen/CGObjC.cpp
+++ lib/CodeGen/CGObjC.cpp
@@ -338,6 +338,69 @@
return nullptr;
}
+/// The ObjC runtime may provide entrypoints that are likely to be faster
+/// than an ordinary message send of the appropriate selector.
+///
+/// The entrypoints are guaranteed to be equivalent to just sending the
+/// corresponding message. If the entrypoint is implemented naively as just a
+/// message send, using it is a trade-off: it sacrifices a few cycles of
+/// overhead to save a small amount of code. However, it's possible for
+/// runtimes to detect and special-case classes that use "standard"
+/// retain/release behavior; if that's dynamically a large proportion of all
+/// retained objects, using the entrypoint will also be faster than using a
+/// message send.
+///
+/// If the runtime does support a required entrypoint, then this method will
+/// generate a call and return the resulting value. Otherwise it will return
+/// None and the caller can generate a msgSend instead.
+static Optional<llvm::Value *>
+tryGenerateSpecializedMessageSend(CodeGenFunction &CGF, QualType ResultType,
+ llvm::Value *Receiver, Selector Sel,
+ const ObjCMethodDecl *method) {
+ auto &CGM = CGF.CGM;
+ if (!CGM.getCodeGenOpts().ObjCConvertMessagesToRuntimeCalls)
+ return None;
+
+ auto &Runtime = CGM.getLangOpts().ObjCRuntime;
+ switch (Sel.getMethodFamily()) {
+ case OMF_alloc:
+ // Make sure the name is exactly 'alloc'. All methods with that
+ // prefix are identified as OMF_alloc but we only want to call the
+ // runtime for this version.
+ if (Runtime.shouldUseRuntimeFunctionsForAlloc() && Sel.isUnarySelector() &&
+ Sel.getNameForSlot(0) == "alloc" &&
+ ResultType->isObjCObjectPointerType())
+ return CGF.EmitObjCAlloc(Receiver, CGF.ConvertType(ResultType));
+ break;
+
+ case OMF_autorelease:
+ if (ResultType->isObjCObjectPointerType() &&
+ CGM.getLangOpts().getGC() == LangOptions::NonGC &&
+ Runtime.shouldUseARCFunctionsForRetainRelease())
+ return CGF.EmitARCAutorelease(Receiver, CGF.ConvertType(ResultType));
+ break;
+
+ case OMF_retain:
+ if (ResultType->isObjCObjectPointerType() &&
+ CGM.getLangOpts().getGC() == LangOptions::NonGC &&
+ Runtime.shouldUseARCFunctionsForRetainRelease())
+ return CGF.EmitARCRetainNonBlock(Receiver, CGF.ConvertType(ResultType));
+ break;
+
+ case OMF_release:
+ if (ResultType->isVoidType() &&
+ CGM.getLangOpts().getGC() == LangOptions::NonGC &&
+ Runtime.shouldUseARCFunctionsForRetainRelease()) {
+ CGF.EmitARCRelease(Receiver, ARCPreciseLifetime);
+ return nullptr;
+ }
+ break;
+ default:
+ break;
+ }
+ return None;
+}
+
RValue CodeGenFunction::EmitObjCMessageExpr(const ObjCMessageExpr *E,
ReturnValueSlot Return) {
// Only the lookup mechanism and first two arguments of the method
@@ -460,10 +523,16 @@
Args,
method);
} else {
- result = Runtime.GenerateMessageSend(*this, Return, ResultType,
- E->getSelector(),
- Receiver, Args, OID,
- method);
+ // Call runtime methods directly if we can.
+ if (Optional<llvm::Value *> SpecializedResult =
+ tryGenerateSpecializedMessageSend(*this, ResultType, Receiver,
+ E->getSelector(), method)) {
+ result = RValue::get(SpecializedResult.getValue());
+ } else {
+ result = Runtime.GenerateMessageSend(*this, Return, ResultType,
+ E->getSelector(), Receiver, Args,
+ OID, method);
+ }
}
// For delegate init calls in ARC, implicitly store the result of
@@ -1814,6 +1883,7 @@
/// where a null input causes a no-op and returns null.
static llvm::Value *emitARCValueOperation(CodeGenFunction &CGF,
llvm::Value *value,
+ llvm::Type *returnType,
llvm::Constant *&fn,
StringRef fnName,
bool isTailCall = false) {
@@ -1826,7 +1896,7 @@
}
// Cast the argument to 'id'.
- llvm::Type *origType = value->getType();
+ llvm::Type *origType = returnType ? returnType : value->getType();
value = CGF.Builder.CreateBitCast(value, CGF.Int8PtrTy);
// Call the function.
@@ -1931,8 +2001,9 @@
/// Retain the given object, with normal retain semantics.
/// call i8* \@objc_retain(i8* %value)
-llvm::Value *CodeGenFunction::EmitARCRetainNonBlock(llvm::Value *value) {
- return emitARCValueOperation(*this, value,
+llvm::Value *CodeGenFunction::EmitARCRetainNonBlock(llvm::Value *value,
+ llvm::Type *returnType) {
+ return emitARCValueOperation(*this, value, returnType,
CGM.getObjCEntrypoints().objc_retain,
"objc_retain");
}
@@ -1946,7 +2017,7 @@
llvm::Value *CodeGenFunction::EmitARCRetainBlock(llvm::Value *value,
bool mandatory) {
llvm::Value *result
- = emitARCValueOperation(*this, value,
+ = emitARCValueOperation(*this, value, nullptr,
CGM.getObjCEntrypoints().objc_retainBlock,
"objc_retainBlock");
@@ -2016,7 +2087,7 @@
llvm::Value *
CodeGenFunction::EmitARCRetainAutoreleasedReturnValue(llvm::Value *value) {
emitAutoreleasedReturnValueMarker(*this);
- return emitARCValueOperation(*this, value,
+ return emitARCValueOperation(*this, value, nullptr,
CGM.getObjCEntrypoints().objc_retainAutoreleasedReturnValue,
"objc_retainAutoreleasedReturnValue");
}
@@ -2031,7 +2102,7 @@
llvm::Value *
CodeGenFunction::EmitARCUnsafeClaimAutoreleasedReturnValue(llvm::Value *value) {
emitAutoreleasedReturnValueMarker(*this);
- return emitARCValueOperation(*this, value,
+ return emitARCValueOperation(*this, value, nullptr,
CGM.getObjCEntrypoints().objc_unsafeClaimAutoreleasedReturnValue,
"objc_unsafeClaimAutoreleasedReturnValue");
}
@@ -2145,8 +2216,9 @@
/// Autorelease the given object.
/// call i8* \@objc_autorelease(i8* %value)
-llvm::Value *CodeGenFunction::EmitARCAutorelease(llvm::Value *value) {
- return emitARCValueOperation(*this, value,
+llvm::Value *CodeGenFunction::EmitARCAutorelease(llvm::Value *value,
+ llvm::Type *resultType) {
+ return emitARCValueOperation(*this, value, resultType,
CGM.getObjCEntrypoints().objc_autorelease,
"objc_autorelease");
}
@@ -2155,7 +2227,7 @@
/// call i8* \@objc_autoreleaseReturnValue(i8* %value)
llvm::Value *
CodeGenFunction::EmitARCAutoreleaseReturnValue(llvm::Value *value) {
- return emitARCValueOperation(*this, value,
+ return emitARCValueOperation(*this, value, nullptr,
CGM.getObjCEntrypoints().objc_autoreleaseReturnValue,
"objc_autoreleaseReturnValue",
/*isTailCall*/ true);
@@ -2165,7 +2237,7 @@
/// call i8* \@objc_retainAutoreleaseReturnValue(i8* %value)
llvm::Value *
CodeGenFunction::EmitARCRetainAutoreleaseReturnValue(llvm::Value *value) {
- return emitARCValueOperation(*this, value,
+ return emitARCValueOperation(*this, value, nullptr,
CGM.getObjCEntrypoints().objc_retainAutoreleaseReturnValue,
"objc_retainAutoreleaseReturnValue",
/*isTailCall*/ true);
@@ -2194,7 +2266,7 @@
/// call i8* \@objc_retainAutorelease(i8* %value)
llvm::Value *
CodeGenFunction::EmitARCRetainAutoreleaseNonBlock(llvm::Value *value) {
- return emitARCValueOperation(*this, value,
+ return emitARCValueOperation(*this, value, nullptr,
CGM.getObjCEntrypoints().objc_retainAutorelease,
"objc_retainAutorelease");
}
@@ -2338,6 +2410,15 @@
return InitRV.getScalarVal();
}
+/// Allocate the given objc object.
+/// call i8* \@objc_alloc(i8* %value)
+llvm::Value *CodeGenFunction::EmitObjCAlloc(llvm::Value *value,
+ llvm::Type *resultType) {
+ return emitARCValueOperation(*this, value, resultType,
+ CGM.getObjCEntrypoints().objc_alloc,
+ "objc_alloc");
+}
+
/// Produce the code to do a primitive release.
/// [tmp drain];
void CodeGenFunction::EmitObjCMRRAutoreleasePoolPop(llvm::Value *Arg) {
Index: include/clang/Frontend/CodeGenOptions.def
===================================================================
--- include/clang/Frontend/CodeGenOptions.def
+++ include/clang/Frontend/CodeGenOptions.def
@@ -98,6 +98,8 @@
CODEGENOPT(NoZeroInitializedInBSS , 1, 0) ///< -fno-zero-initialized-in-bss.
/// \brief Method of Objective-C dispatch to use.
ENUM_CODEGENOPT(ObjCDispatchMethod, ObjCDispatchMethodKind, 2, Legacy)
+/// Replace certain message sends with calls to ObjC runtime entrypoints
+CODEGENOPT(ObjCConvertMessagesToRuntimeCalls , 1, 1)
CODEGENOPT(OmitLeafFramePointer , 1, 0) ///< Set when -momit-leaf-frame-pointer is
///< enabled.
VALUE_CODEGENOPT(OptimizationLevel, 2, 0) ///< The -O[0-3] option specified.
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -933,6 +933,10 @@
def fobjc_arc : Flag<["-"], "fobjc-arc">, Group<f_Group>, Flags<[CC1Option]>,
HelpText<"Synthesize retain and release calls for Objective-C pointers">;
def fno_objc_arc : Flag<["-"], "fno-objc-arc">, Group<f_Group>;
+def fobjc_convert_messages_to_runtime_calls :
+ Flag<["-"], "fobjc-convert-messages-to-runtime-calls">, Group<f_Group>;
+def fno_objc_convert_messages_to_runtime_calls :
+ Flag<["-"], "fno-objc-convert-messages-to-runtime-calls">, Group<f_Group>, Flags<[CC1Option]>;
def fobjc_arc_exceptions : Flag<["-"], "fobjc-arc-exceptions">, Group<f_Group>, Flags<[CC1Option]>,
HelpText<"Use EH-safe code when synthesizing retains and releases in -fobjc-arc">;
def fno_objc_arc_exceptions : Flag<["-"], "fno-objc-arc-exceptions">, Group<f_Group>;
Index: include/clang/Basic/ObjCRuntime.h
===================================================================
--- include/clang/Basic/ObjCRuntime.h
+++ include/clang/Basic/ObjCRuntime.h
@@ -171,6 +171,79 @@
llvm_unreachable("bad kind");
}
+ /// Does this runtime provide ARC entrypoints that are likely to be faster
+ /// than an ordinary message send of the appropriate selector?
+ ///
+ /// The ARC entrypoints are guaranteed to be equivalent to just sending the
+ /// corresponding message. If the entrypoint is implemented naively as just a
+ /// message send, using it is a trade-off: it sacrifices a few cycles of
+ /// overhead to save a small amount of code. However, it's possible for
+ /// runtimes to detect and special-case classes that use "standard"
+ /// retain/release behavior; if that's dynamically a large proportion of all
+ /// retained objects, using the entrypoint will also be faster than using a
+ /// message send.
+ ///
+ /// When this method returns true, Clang will turn non-super message sends of
+ /// certain selectors into calls to the correspond entrypoint:
+ /// retain => objc_retain
+ /// release => objc_release
+ bool shouldUseARCFunctionsForRetainRelease() const {
+ switch (getKind()) {
+ case FragileMacOSX:
+ return false;
+ case MacOSX:
+ return getVersion() >= VersionTuple(10, 10);
+ case iOS:
+ return getVersion() >= VersionTuple(8);
+ case WatchOS:
+ return true;
+
+ case GCC:
+ return false;
+ case GNUstep:
+ return false;
+ case ObjFW:
+ return false;
+ }
+ llvm_unreachable("bad kind");
+ }
+
+ /// Does this runtime provide entrypoints that are likely to be faster
+ /// than an ordinary message send of the "alloc" selector?
+ ///
+ /// The "alloc" entrypoint is guaranteed to be equivalent to just sending the
+ /// corresponding message. If the entrypoint is implemented naively as just a
+ /// message send, using it is a trade-off: it sacrifices a few cycles of
+ /// overhead to save a small amount of code. However, it's possible for
+ /// runtimes to detect and special-case classes that use "standard"
+ /// alloc behavior; if that's dynamically a large proportion of all
+ /// objects, using the entrypoint will also be faster than using a message
+ /// send.
+ ///
+ /// When this method returns true, Clang will turn non-super message sends of
+ /// certain selectors into calls to the correspond entrypoint:
+ /// alloc => objc_alloc
+ bool shouldUseRuntimeFunctionsForAlloc() const {
+ switch (getKind()) {
+ case FragileMacOSX:
+ return false;
+ case MacOSX:
+ return getVersion() >= VersionTuple(10, 10);
+ case iOS:
+ return getVersion() >= VersionTuple(8);
+ case WatchOS:
+ return true;
+
+ case GCC:
+ return false;
+ case GNUstep:
+ return false;
+ case ObjFW:
+ return false;
+ }
+ llvm_unreachable("bad kind");
+ }
+
/// \brief Does this runtime supports optimized setter entrypoints?
bool hasOptimizedSetter() const {
switch (getKind()) {
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