From 361b11dedac9bb7a4860c7895c2b74f052e0470c Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanaka@apple.com>
Date: Fri, 13 Nov 2015 00:42:21 +0000
Subject: [PATCH] Add support for function attribute 'disable_tail_calls'.
The ``disable_tail_calls`` attribute instructs the backend to not
perform tail call optimization inside the marked function.
For example,
int callee(int);
int foo(int a) __attribute__((disable_tail_calls)) {
return callee(a); // This call is not tail-call optimized.
}
Note that this attribute is different from 'not_tail_called', which
prevents tail-call optimization to the marked function.
rdar://problem/8973573
Differential Revision: http://reviews.llvm.org/D12547
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@252986 91177308-0d34-0410-b5e6-96231b3b80d8
---
include/clang/Basic/Attr.td | 7 ++++
include/clang/Basic/AttrDocs.td | 38 +++++++++++++++++++++
lib/CodeGen/CGCall.cpp | 6 +++-
lib/Sema/SemaDeclAttr.cpp | 24 ++++++++++++-
test/CodeGen/attr-disable-tail-calls.c | 18 +++++++---
test/CodeGenCXX/attr-disable-tail-calls.cpp | 35 +++++++++++++++++++
test/Sema/attr-disable-tail-calls.c | 13 +++++++
test/SemaCXX/attr-disable-tail-calls.cpp | 8 +++++
8 files changed, 142 insertions(+), 7 deletions(-)
create mode 100644 test/CodeGenCXX/attr-disable-tail-calls.cpp
create mode 100644 test/Sema/attr-disable-tail-calls.c
create mode 100644 test/SemaCXX/attr-disable-tail-calls.cpp
diff --git a/include/clang/Basic/Attr.td b/include/clang/Basic/Attr.td
index a32a8788e69..e020227612b 100644
--- a/include/clang/Basic/Attr.td
+++ b/include/clang/Basic/Attr.td
@@ -890,6 +890,13 @@ def ReturnsTwice : InheritableAttr {
let Documentation = [Undocumented];
}
+def DisableTailCalls : InheritableAttr {
+ let Spellings = [GNU<"disable_tail_calls">,
+ CXX11<"clang", "disable_tail_calls">];
+ let Subjects = SubjectList<[Function, ObjCMethod]>;
+ let Documentation = [DisableTailCallsDocs];
+}
+
def NoAlias : InheritableAttr {
let Spellings = [Declspec<"noalias">];
let Subjects = SubjectList<[Function]>;
diff --git a/include/clang/Basic/AttrDocs.td b/include/clang/Basic/AttrDocs.td
index b28ef6df0ed..9f933ba5249 100644
--- a/include/clang/Basic/AttrDocs.td
+++ b/include/clang/Basic/AttrDocs.td
@@ -1684,3 +1684,41 @@ this attribute affects all methods and static data members of that class.
This can be used to contain the ABI of a C++ library by excluding unwanted class methods from the export tables.
}];
}
+
+def DisableTailCallsDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+The ``disable_tail_calls`` attribute instructs the backend to not perform tail call optimization inside the marked function.
+
+For example:
+
+ .. code-block:: c
+
+ int callee(int);
+
+ int foo(int a) __attribute__((disable_tail_calls)) {
+ return callee(a); // This call is not tail-call optimized.
+ }
+
+Marking virtual functions as ``disable_tail_calls`` is legal.
+
+ .. code-block: c++
+
+ int callee(int);
+
+ class Base {
+ public:
+ [[clang::disable_tail_calls]] virtual int foo1() {
+ return callee(); // This call is not tail-call optimized.
+ }
+ };
+
+ class Derived1 : public Base {
+ public:
+ int foo1() override {
+ return callee(); // This call is tail-call optimized.
+ }
+ };
+
+ }];
+}
diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 430184d4398..5dea876451f 100644
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -1481,8 +1481,12 @@ void CodeGenModule::ConstructAttributeList(const CGFunctionInfo &FI,
FuncAttrs.addAttribute("no-frame-pointer-elim-non-leaf");
}
+ bool DisableTailCalls =
+ CodeGenOpts.DisableTailCalls ||
+ (TargetDecl && TargetDecl->hasAttr<DisableTailCallsAttr>());
FuncAttrs.addAttribute("disable-tail-calls",
- llvm::toStringRef(CodeGenOpts.DisableTailCalls));
+ llvm::toStringRef(DisableTailCalls));
+
FuncAttrs.addAttribute("less-precise-fpmad",
llvm::toStringRef(CodeGenOpts.LessPreciseFPMAD));
FuncAttrs.addAttribute("no-infs-fp-math",
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index a9473d2e119..abdab9a0692 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -1583,6 +1583,15 @@ static void handleCommonAttr(Sema &S, Decl *D, const AttributeList &Attr) {
D->addAttr(CA);
}
+static void handleNakedAttr(Sema &S, Decl *D, const AttributeList &Attr) {
+ if (checkAttrMutualExclusion<DisableTailCallsAttr>(S, D, Attr.getRange(),
+ Attr.getName()))
+ return;
+
+ D->addAttr(::new (S.Context) NakedAttr(Attr.getRange(), S.Context,
+ Attr.getAttributeSpellingListIndex()));
+}
+
static void handleNoReturnAttr(Sema &S, Decl *D, const AttributeList &attr) {
if (hasDeclarator(D)) return;
@@ -1713,6 +1722,16 @@ static void handleNotTailCalledAttr(Sema &S, Decl *D,
Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
}
+static void handleDisableTailCallsAttr(Sema &S, Decl *D,
+ const AttributeList &Attr) {
+ if (checkAttrMutualExclusion<NakedAttr>(S, D, Attr.getRange(),
+ Attr.getName()))
+ return;
+
+ D->addAttr(::new (S.Context) DisableTailCallsAttr(
+ Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
+}
+
static void handleUsedAttr(Sema &S, Decl *D, const AttributeList &Attr) {
if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
if (VD->hasLocalStorage()) {
@@ -4933,7 +4952,7 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
handleHotAttr(S, D, Attr);
break;
case AttributeList::AT_Naked:
- handleSimpleAttribute<NakedAttr>(S, D, Attr);
+ handleNakedAttr(S, D, Attr);
break;
case AttributeList::AT_NoReturn:
handleNoReturnAttr(S, D, Attr);
@@ -5056,6 +5075,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
case AttributeList::AT_NotTailCalled:
handleNotTailCalledAttr(S, D, Attr);
break;
+ case AttributeList::AT_DisableTailCalls:
+ handleDisableTailCallsAttr(S, D, Attr);
+ break;
case AttributeList::AT_Used:
handleUsedAttr(S, D, Attr);
break;
diff --git a/test/CodeGen/attr-disable-tail-calls.c b/test/CodeGen/attr-disable-tail-calls.c
index 81413492ff3..d47b14fe8ba 100644
--- a/test/CodeGen/attr-disable-tail-calls.c
+++ b/test/CodeGen/attr-disable-tail-calls.c
@@ -1,11 +1,19 @@
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.7.0 %s -emit-llvm -mdisable-tail-calls -o - | FileCheck %s -check-prefix=CHECK -check-prefix=DISABLE
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.7.0 %s -emit-llvm -o - | FileCheck %s -check-prefix=CHECK -check-prefix=ENABLE
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.7.0 %s -emit-llvm -mdisable-tail-calls -o - | FileCheck %s -check-prefix=DISABLE
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.7.0 %s -emit-llvm -o - | FileCheck %s -check-prefix=ENABLE
-// CHECK: define i32 @f1() [[ATTR:#[0-9]+]] {
+// DISABLE: define i32 @f1() [[ATTRTRUE:#[0-9]+]] {
+// DISABLE: define i32 @f2() [[ATTRTRUE]] {
+// ENABLE: define i32 @f1() [[ATTRFALSE:#[0-9]+]] {
+// ENABLE: define i32 @f2() [[ATTRTRUE:#[0-9]+]] {
int f1() {
return 0;
}
-// DISABLE: attributes [[ATTR]] = { {{.*}} "disable-tail-calls"="true" {{.*}} }
-// ENABLE: attributes [[ATTR]] = { {{.*}} "disable-tail-calls"="false" {{.*}} }
+int f2() __attribute__((disable_tail_calls)) {
+ return 0;
+}
+
+// DISABLE: attributes [[ATTRTRUE]] = { {{.*}}"disable-tail-calls"="true"{{.*}} }
+// ENABLE: attributes [[ATTRFALSE]] = { {{.*}}"disable-tail-calls"="false"{{.*}} }
+// ENABLE: attributes [[ATTRTRUE]] = { {{.*}}"disable-tail-calls"="true"{{.*}} }
diff --git a/test/CodeGenCXX/attr-disable-tail-calls.cpp b/test/CodeGenCXX/attr-disable-tail-calls.cpp
new file mode 100644
index 00000000000..b9a3c2712f0
--- /dev/null
+++ b/test/CodeGenCXX/attr-disable-tail-calls.cpp
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -triple=x86_64-apple-darwin -std=c++11 -emit-llvm -o - %s | FileCheck %s
+
+class B {
+public:
+ [[clang::disable_tail_calls]] virtual int m1() { return 1; }
+ virtual int m2() { return 2; }
+ int m3() { return 3; }
+ [[clang::disable_tail_calls]] int m4();
+};
+
+class D : public B {
+public:
+ int m1() override { return 11; }
+ [[clang::disable_tail_calls]] int m2() override { return 22; }
+};
+
+int foo1() {
+ B *b = new B;
+ D *d = new D;
+ int t = 0;
+ t += b->m1() + b->m2() + b->m3() + b->m4();
+ t += d->m1() + d->m2();
+ return t;
+}
+
+// CHECK: define linkonce_odr i32 @_ZN1B2m3Ev(%class.B* %this) [[ATTRFALSE:#[0-9]+]]
+// CHECK: declare i32 @_ZN1B2m4Ev(%class.B*) [[ATTRTRUE0:#[0-9]+]]
+// CHECK: define linkonce_odr i32 @_ZN1B2m1Ev(%class.B* %this) unnamed_addr [[ATTRTRUE1:#[0-9]+]]
+// CHECK: define linkonce_odr i32 @_ZN1B2m2Ev(%class.B* %this) unnamed_addr [[ATTRFALSE:#[0-9]+]]
+// CHECK: define linkonce_odr i32 @_ZN1D2m1Ev(%class.D* %this) unnamed_addr [[ATTRFALSE:#[0-9]+]]
+// CHECK: define linkonce_odr i32 @_ZN1D2m2Ev(%class.D* %this) unnamed_addr [[ATTRTRUE1:#[0-9]+]]
+
+// CHECK: attributes [[ATTRFALSE]] = { {{.*}}"disable-tail-calls"="false"{{.*}} }
+// CHECK: attributes [[ATTRTRUE0]] = { {{.*}}"disable-tail-calls"="true"{{.*}} }
+// CHECK: attributes [[ATTRTRUE1]] = { {{.*}}"disable-tail-calls"="true"{{.*}} }
diff --git a/test/Sema/attr-disable-tail-calls.c b/test/Sema/attr-disable-tail-calls.c
new file mode 100644
index 00000000000..4574d5e0b66
--- /dev/null
+++ b/test/Sema/attr-disable-tail-calls.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void __attribute__((disable_tail_calls,naked)) foo1(int a) { // expected-error {{'disable_tail_calls' and 'naked' attributes are not compatible}} expected-note {{conflicting attribute is here}}
+ __asm__("");
+}
+
+void __attribute__((naked,disable_tail_calls)) foo2(int a) { // expected-error {{'naked' and 'disable_tail_calls' attributes are not compatible}} expected-note {{conflicting attribute is here}}
+ __asm__("");
+}
+
+int g0 __attribute__((disable_tail_calls)); // expected-warning {{'disable_tail_calls' attribute only applies to functions and methods}}
+
+int foo3(int a) __attribute__((disable_tail_calls("abc"))); // expected-error {{'disable_tail_calls' attribute takes no arguments}}
diff --git a/test/SemaCXX/attr-disable-tail-calls.cpp b/test/SemaCXX/attr-disable-tail-calls.cpp
new file mode 100644
index 00000000000..d442aa6d440
--- /dev/null
+++ b/test/SemaCXX/attr-disable-tail-calls.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+class B {
+public:
+ [[clang::disable_tail_calls]] virtual int foo1() { return 1; }
+ [[clang::disable_tail_calls]] int foo2() { return 2; }
+};
--
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