ahatanak created this revision.
ahatanak added a reviewer: rjmccall.
This patch adds a command line option (-fdisable-tail-calls-esca
ping-blocks) that annotates escaping block invoke functions with attribute
"disable-tail-calls". This is an option that helps users in debugging their
code who spend a lot of time trying to figure out where a block came from.
The user who is asking for this command line option does not want to disable
tail-call optimization for non-escaping blocks. For example, in the following
code, we should not disable tail-call optimization for the block that is
directly passed to function "noescapefunc":
void foo3(void);
void foo1() {
noescapefunc(^{ foo3(); }); // do not disable tail-call.
BlockTy b = ^{ foo3(); }; // disable tail-call.
noescapefunc(b);
}
Ideally, I think we want to avoid disabling tail-call optimization for block
"b" too, as it doesn't escape. However, this patch doesn't do anything to avoid
disabling tail-call optimization for the block, since that would require a more
complex analysis.
rdar://problem/35758207
https://reviews.llvm.org/D43841
Files:
include/clang/AST/DeclObjC.h
include/clang/AST/Type.h
include/clang/Driver/Options.td
include/clang/Frontend/CodeGenOptions.def
lib/AST/DeclObjC.cpp
lib/AST/Type.cpp
lib/CodeGen/CGCall.cpp
lib/CodeGen/CodeGenFunction.h
lib/CodeGen/CodeGenModule.h
lib/Driver/ToolChains/Clang.cpp
lib/Frontend/CompilerInvocation.cpp
test/CodeGenObjC/disable-tail-call-escaping-block.m
test/Driver/fdisable-tail-calls-escaping-blocks.c
Index: test/Driver/fdisable-tail-calls-escaping-blocks.c
===================================================================
--- /dev/null
+++ test/Driver/fdisable-tail-calls-escaping-blocks.c
@@ -0,0 +1,7 @@
+// RUN: %clang -### %s -fno-disable-tail-calls-escaping-blocks -fdisable-tail-calls-escaping-blocks 2> %t
+// RUN: FileCheck --check-prefix=CHECK-DISABLE < %t %s
+// CHECK-DISABLE: "-fdisable-tail-calls-escaping-blocks"
+
+// RUN: %clang -### %s -fdisable-tail-calls-escaping-blocks -fno-disable-tail-calls-escaping-blocks 2> %t
+// RUN: FileCheck --check-prefix=CHECK-NO-DISABLE < %t %s
+// CHECK-NO-DISABLE-NOT: "-fdisable-tail-calls-escaping-blocks"
Index: test/CodeGenObjC/disable-tail-call-escaping-block.m
===================================================================
--- /dev/null
+++ test/CodeGenObjC/disable-tail-call-escaping-block.m
@@ -0,0 +1,47 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -fblocks -fdisable-tail-calls-escaping-blocks -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-LABEL: define void @test(
+// CHECK: store i8* bitcast (void (i8*)* @[[TEST_BLOCK_INVOKE0:.*]] to i8*)
+// CHECK: store i8* bitcast (void (i8*)* @[[TEST_BLOCK_INVOKE1:.*]] to i8*)
+// CHECK: store i8* bitcast (void (i8*)* @[[TEST_BLOCK_INVOKE2:.*]] to i8*)
+// CHECK: store i8* bitcast (void (i8*)* @[[TEST_BLOCK_INVOKE3:.*]] to i8*)
+// CHECK: store i8* bitcast (void (i8*)* @[[TEST_BLOCK_INVOKE4:.*]] to i8*)
+// CHECK: store i8* bitcast (void (i8*)* @[[TEST_BLOCK_INVOKE5:.*]] to i8*)
+
+// CHECK: define internal void @[[TEST_BLOCK_INVOKE0]]({{.*}}) #[[DISABLEATTR:.*]] {
+// CHECK: define internal void @[[TEST_BLOCK_INVOKE1]]({{.*}}) #[[ENABLEATTR:.*]] {
+// CHECK: define internal void @[[TEST_BLOCK_INVOKE2]]({{.*}}) #[[DISABLEATTR]] {
+// CHECK: define internal void @[[TEST_BLOCK_INVOKE3]]({{.*}}) #[[DISABLEATTR]] {
+// CHECK: define internal void @[[TEST_BLOCK_INVOKE4]]({{.*}}) #[[ENABLEATTR]] {
+// CHECK: define internal void @[[TEST_BLOCK_INVOKE5]]({{.*}}) #[[DISABLEATTR]] {
+
+// CHECK: attributes #[[ENABLEATTR]] = {{{.*}}"disable-tail-calls"="false"{{.*}}}
+// CHECK: attributes #[[DISABLEATTR]] = {{{.*}}"disable-tail-calls"="true"{{.*}}}
+
+typedef void (^BlockTy)(void);
+
+void callee0(__attribute__((noescape)) BlockTy);
+void callee1(BlockTy);
+
+__attribute__((objc_root_class))
+@interface C0
+-(void)m0:(__attribute__((noescape)) BlockTy)p;
+-(void)m1:(BlockTy)p;
+@end
+
+@implementation C0
+-(void)m0:(__attribute__((noescape)) BlockTy)p {}
+-(void)m1:(BlockTy)p {}
+@end
+
+void test(id a, C0 *c0) {
+ BlockTy b0 = ^{ (void)a; }; // disable tail-call optimization.
+ callee0(b0);
+ callee0(^{ (void)a; }); // enable tail-call optimization.
+ callee1(^{ (void)a; }); // disable tail-call optimization.
+
+ BlockTy b1 = ^{ (void)a; }; // disable tail-call optimization.
+ [c0 m0:b1];
+ [c0 m0:^{ (void)a; }]; // enable tail-call optimization.
+ [c0 m1:^{ (void)a; }]; // disable tail-call optimization.
+}
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -639,6 +639,8 @@
Opts.DisableFree = Args.hasArg(OPT_disable_free);
Opts.DiscardValueNames = Args.hasArg(OPT_discard_value_names);
Opts.DisableTailCalls = Args.hasArg(OPT_mdisable_tail_calls);
+ Opts.DisableTailCallsEscapingBlocks =
+ Args.hasArg(OPT_fdisable_tail_calls_escaping_blocks);
Opts.FloatABI = Args.getLastArgValue(OPT_mfloat_abi);
Opts.LessPreciseFPMAD = Args.hasArg(OPT_cl_mad_enable) ||
Args.hasArg(OPT_cl_unsafe_math_optimizations) ||
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -3439,6 +3439,9 @@
if (!Args.hasFlag(options::OPT_foptimize_sibling_calls,
options::OPT_fno_optimize_sibling_calls))
CmdArgs.push_back("-mdisable-tail-calls");
+ if (Args.hasFlag(options::OPT_fdisable_tail_calls_escaping_blocks,
+ options::OPT_fno_disable_tail_calls_escaping_blocks))
+ CmdArgs.push_back("-fdisable-tail-calls-escaping-blocks");
Args.AddLastArg(CmdArgs, options::OPT_ffine_grained_bitfield_accesses,
options::OPT_fno_fine_grained_bitfield_accesses);
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -466,6 +466,8 @@
/// them if the constexpr evaluator gets aggressive.
llvm::DenseMap<const BlockExpr *, llvm::Constant *> EmittedGlobalBlocks;
+ llvm::SmallPtrSet<const BlockDecl *, 1> NoEscapeBlocks;
+
/// @name Cache for Blocks Runtime Globals
/// @{
@@ -554,6 +556,16 @@
return *ObjCData;
}
+ bool isEscapingBlock(const Decl *D) {
+ if (const auto *BD = dyn_cast<BlockDecl>(D))
+ return !NoEscapeBlocks.count(BD);
+ return false;
+ }
+
+ void addNoEscapeBlock(const BlockDecl *BD) {
+ NoEscapeBlocks.insert(BD);
+ }
+
// Version checking function, used to implement ObjC's @available:
// i32 @__isOSVersionAtLeast(i32, i32, i32)
llvm::Constant *IsOSVersionAtLeastFn = nullptr;
Index: lib/CodeGen/CodeGenFunction.h
===================================================================
--- lib/CodeGen/CodeGenFunction.h
+++ lib/CodeGen/CodeGenFunction.h
@@ -3940,9 +3940,11 @@
#endif
// First, use the argument types that the type info knows about
+ unsigned Idx = ParamsToSkip;
+
for (auto I = CallArgTypeInfo->param_type_begin() + ParamsToSkip,
E = CallArgTypeInfo->param_type_end();
- I != E; ++I, ++Arg) {
+ I != E; ++I, ++Arg, ++Idx) {
assert(Arg != ArgRange.end() && "Running over edge of argument list!");
assert((isGenericMethod ||
((*I)->isVariablyModifiedType() ||
@@ -3955,6 +3957,11 @@
.getTypePtr())) &&
"type mismatch in call argument!");
ArgTypes.push_back(*I);
+ if (CGM.getCodeGenOpts().DisableTailCallsEscapingBlocks &&
+ CallArgTypeInfo->isNoEscapeParam(Idx))
+ if (const auto *BE = dyn_cast<BlockExpr>(
+ (*Arg)->IgnoreParenNoopCasts(getContext())))
+ CGM.addNoEscapeBlock(BE->getBlockDecl());
}
}
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -1871,10 +1871,15 @@
}
if (!AttrOnCallSite) {
- bool DisableTailCalls =
- CodeGenOpts.DisableTailCalls ||
- (TargetDecl && (TargetDecl->hasAttr<DisableTailCallsAttr>() ||
- TargetDecl->hasAttr<AnyX86InterruptAttr>()));
+ bool DisableTailCalls = CodeGenOpts.DisableTailCalls;
+
+ if (TargetDecl &&
+ ((TargetDecl->hasAttr<DisableTailCallsAttr>() ||
+ TargetDecl->hasAttr<AnyX86InterruptAttr>()) ||
+ (CodeGenOpts.DisableTailCallsEscapingBlocks &&
+ isEscapingBlock(TargetDecl))))
+ DisableTailCalls = true;
+
FuncAttrs.addAttribute("disable-tail-calls",
llvm::toStringRef(DisableTailCalls));
GetCPUAndFeaturesAttributes(TargetDecl, FuncAttrs);
Index: lib/AST/Type.cpp
===================================================================
--- lib/AST/Type.cpp
+++ lib/AST/Type.cpp
@@ -2813,6 +2813,10 @@
}
}
+bool FunctionProtoType::isNoEscapeParam(unsigned Idx) const {
+ return getExtParameterInfo(Idx).isNoEscape();
+}
+
bool FunctionProtoType::hasDependentExceptionSpec() const {
if (Expr *NE = getNoexceptExpr())
return NE->isValueDependent();
Index: lib/AST/DeclObjC.cpp
===================================================================
--- lib/AST/DeclObjC.cpp
+++ lib/AST/DeclObjC.cpp
@@ -854,6 +854,11 @@
setParamsAndSelLocs(C, Params, SelLocs);
}
+bool ObjCMethodDecl::isNoEscapeParam(unsigned Idx) const {
+ assert(Idx < param_size() && "Index too large");
+ return (*(param_begin() + Idx))->hasAttr<NoEscapeAttr>();
+}
+
/// \brief A definition will return its interface declaration.
/// An interface declaration will return its definition.
/// Otherwise it will return itself.
Index: include/clang/Frontend/CodeGenOptions.def
===================================================================
--- include/clang/Frontend/CodeGenOptions.def
+++ include/clang/Frontend/CodeGenOptions.def
@@ -62,6 +62,8 @@
///< pass manager.
CODEGENOPT(DisableRedZone , 1, 0) ///< Set when -mno-red-zone is enabled.
CODEGENOPT(DisableTailCalls , 1, 0) ///< Do not emit tail calls.
+CODEGENOPT(DisableTailCallsEscapingBlocks, 1, 0) ///< Do not emit tail calls for
+ ///< escaping blocks.
CODEGENOPT(EmitDeclMetadata , 1, 0) ///< Emit special metadata indicating what
///< Decl* various IR entities came from.
///< Only useful when running CodeGen as a
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1415,6 +1415,8 @@
HelpText<"Disable OpenMP code for SIMD-based constructs.">;
def fno_optimize_sibling_calls : Flag<["-"], "fno-optimize-sibling-calls">, Group<f_Group>;
def foptimize_sibling_calls : Flag<["-"], "foptimize-sibling-calls">, Group<f_Group>;
+def fno_disable_tail_calls_escaping_blocks : Flag<["-"], "fno-disable-tail-calls-escaping-blocks">, Group<f_Group>, Flags<[CC1Option]>;
+def fdisable_tail_calls_escaping_blocks : Flag<["-"], "fdisable-tail-calls-escaping-blocks">, Group<f_Group>, Flags<[CC1Option]>;
def force__cpusubtype__ALL : Flag<["-"], "force_cpusubtype_ALL">;
def force__flat__namespace : Flag<["-"], "force_flat_namespace">;
def force__load : Separate<["-"], "force_load">;
Index: include/clang/AST/Type.h
===================================================================
--- include/clang/AST/Type.h
+++ include/clang/AST/Type.h
@@ -3503,6 +3503,8 @@
return llvm::makeArrayRef(param_type_begin(), param_type_end());
}
+ bool isNoEscapeParam(unsigned Idx) const;
+
ExtProtoInfo getExtProtoInfo() const {
ExtProtoInfo EPI;
EPI.ExtInfo = getExtInfo();
Index: include/clang/AST/DeclObjC.h
===================================================================
--- include/clang/AST/DeclObjC.h
+++ include/clang/AST/DeclObjC.h
@@ -414,6 +414,8 @@
ArrayRef<ParmVarDecl*> Params,
ArrayRef<SourceLocation> SelLocs = llvm::None);
+ bool isNoEscapeParam(unsigned Idx) const;
+
// Iterator access to parameter types.
struct GetTypeFn {
QualType operator()(const ParmVarDecl *PD) const { return PD->getType(); }
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