gulfem created this revision.
Herald added subscribers: llvm-commits, cfe-commits, dexonsmith, jdoerfert,
steven_wu, hiraditya.
Herald added a reviewer: aaron.ballman.
Herald added projects: clang, LLVM.
gulfem requested review of this revision.
GCC supports __attribute__((leaf)) as an optimization hint described in:
https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/Function-Attributes.html
This patch adds support for this attribute in Clang/LLVM.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D90275
Files:
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/AttrDocs.td
clang/lib/CodeGen/CGCall.cpp
clang/lib/Sema/SemaDeclAttr.cpp
clang/test/Sema/attr-leaf.c
llvm/include/llvm/Bitcode/LLVMBitCodes.h
llvm/include/llvm/IR/Attributes.td
llvm/lib/AsmParser/LLLexer.cpp
llvm/lib/AsmParser/LLParser.cpp
llvm/lib/AsmParser/LLToken.h
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
llvm/lib/IR/Attributes.cpp
llvm/lib/IR/Verifier.cpp
llvm/lib/Transforms/Utils/CodeExtractor.cpp
Index: llvm/lib/Transforms/Utils/CodeExtractor.cpp
===================================================================
--- llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -906,6 +906,7 @@
case Attribute::NoRecurse:
case Attribute::InlineHint:
case Attribute::MinSize:
+ case Attribute::NoCallback:
case Attribute::NoDuplicate:
case Attribute::NoFree:
case Attribute::NoImplicitFloat:
Index: llvm/lib/IR/Verifier.cpp
===================================================================
--- llvm/lib/IR/Verifier.cpp
+++ llvm/lib/IR/Verifier.cpp
@@ -1572,6 +1572,7 @@
case Attribute::NoReturn:
case Attribute::NoSync:
case Attribute::WillReturn:
+ case Attribute::NoCallback:
case Attribute::NoCfCheck:
case Attribute::NoUnwind:
case Attribute::NoInline:
Index: llvm/lib/IR/Attributes.cpp
===================================================================
--- llvm/lib/IR/Attributes.cpp
+++ llvm/lib/IR/Attributes.cpp
@@ -371,6 +371,8 @@
return "noalias";
if (hasAttribute(Attribute::NoBuiltin))
return "nobuiltin";
+ if (hasAttribute(Attribute::NoCallback))
+ return "nocallback";
if (hasAttribute(Attribute::NoCapture))
return "nocapture";
if (hasAttribute(Attribute::NoDuplicate))
Index: llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -643,6 +643,8 @@
return bitc::ATTR_KIND_NO_ALIAS;
case Attribute::NoBuiltin:
return bitc::ATTR_KIND_NO_BUILTIN;
+ case Attribute::NoCallback:
+ return bitc::ATTR_KIND_NO_CALLBACK;
case Attribute::NoCapture:
return bitc::ATTR_KIND_NO_CAPTURE;
case Attribute::NoDuplicate:
Index: llvm/lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1433,6 +1433,8 @@
return Attribute::NoAlias;
case bitc::ATTR_KIND_NO_BUILTIN:
return Attribute::NoBuiltin;
+ case bitc::ATTR_KIND_NO_CALLBACK:
+ return Attribute::NoCallback;
case bitc::ATTR_KIND_NO_CAPTURE:
return Attribute::NoCapture;
case bitc::ATTR_KIND_NO_DUPLICATE:
Index: llvm/lib/AsmParser/LLToken.h
===================================================================
--- llvm/lib/AsmParser/LLToken.h
+++ llvm/lib/AsmParser/LLToken.h
@@ -198,6 +198,7 @@
kw_noalias,
kw_noundef,
kw_nobuiltin,
+ kw_nocallback,
kw_nocapture,
kw_noduplicate,
kw_nofree,
Index: llvm/lib/AsmParser/LLParser.cpp
===================================================================
--- llvm/lib/AsmParser/LLParser.cpp
+++ llvm/lib/AsmParser/LLParser.cpp
@@ -1314,6 +1314,9 @@
break;
case lltok::kw_naked: B.addAttribute(Attribute::Naked); break;
case lltok::kw_nobuiltin: B.addAttribute(Attribute::NoBuiltin); break;
+ case lltok::kw_nocallback:
+ B.addAttribute(Attribute::NoCallback);
+ break;
case lltok::kw_noduplicate: B.addAttribute(Attribute::NoDuplicate); break;
case lltok::kw_nofree: B.addAttribute(Attribute::NoFree); break;
case lltok::kw_noimplicitfloat:
Index: llvm/lib/AsmParser/LLLexer.cpp
===================================================================
--- llvm/lib/AsmParser/LLLexer.cpp
+++ llvm/lib/AsmParser/LLLexer.cpp
@@ -651,6 +651,7 @@
KEYWORD(nest);
KEYWORD(noalias);
KEYWORD(nobuiltin);
+ KEYWORD(nocallback);
KEYWORD(nocapture);
KEYWORD(noduplicate);
KEYWORD(nofree);
Index: llvm/include/llvm/IR/Attributes.td
===================================================================
--- llvm/include/llvm/IR/Attributes.td
+++ llvm/include/llvm/IR/Attributes.td
@@ -91,6 +91,10 @@
/// Callee isn't recognized as a builtin.
def NoBuiltin : EnumAttr<"nobuiltin">;
+/// leaf function attribute
+def NoCallback : EnumAttr<"nocallback">;
+// def Leaf : EnumAttr<"leaf">;
+
/// Function creates no aliases of pointer.
def NoCapture : EnumAttr<"nocapture">;
Index: llvm/include/llvm/Bitcode/LLVMBitCodes.h
===================================================================
--- llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -652,6 +652,7 @@
ATTR_KIND_BYREF = 69,
ATTR_KIND_MUSTPROGRESS = 70,
ATTR_KIND_NO_STACK_PROTECT = 71,
+ ATTR_KIND_NO_CALLBACK = 72,
};
enum ComdatSelectionKindCodes {
Index: clang/test/Sema/attr-leaf.c
===================================================================
--- /dev/null
+++ clang/test/Sema/attr-leaf.c
@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -verify -fsyntax-only %s
+// expected-no-diagnostics
+
+void f(void) __attribute__((leaf));
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -7590,6 +7590,9 @@
case ParsedAttr::AT_AnyX86NoCfCheck:
handleNoCfCheckAttr(S, D, AL);
break;
+ case ParsedAttr::AT_Leaf:
+ handleSimpleAttribute<LeafAttr>(S, D, AL);
+ break;
case ParsedAttr::AT_NoThrow:
if (!AL.isUsedAsTypeAttr())
handleSimpleAttribute<NoThrowAttr>(S, D, AL);
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -1988,6 +1988,8 @@
FuncAttrs.addAttribute("no_caller_saved_registers");
if (TargetDecl->hasAttr<AnyX86NoCfCheckAttr>())
FuncAttrs.addAttribute(llvm::Attribute::NoCfCheck);
+ if (TargetDecl->hasAttr<LeafAttr>())
+ FuncAttrs.addAttribute(llvm::Attribute::NoCallback);
HasOptnone = TargetDecl->hasAttr<OptimizeNoneAttr>();
if (auto *AllocSize = TargetDecl->getAttr<AllocSizeAttr>()) {
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -3901,6 +3901,19 @@
}];
}
+def LeafDocs : Documentation {
+ let Category = DocCatVariable;
+ let Content = [{
+
+The ``leaf`` attribute is used as a compiler hint to improve dataflow analysis in library functions.
+Functions marked as ``leaf`` attribute are not allowed to enter their caller's translation unit.
+Therefore, they cannot use or modify any data that does not escape the current compilation unit.
+
+For more information see
+`gcc documentation <https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Function-Attributes.html>`
+}];
+}
+
def NoStackProtectorDocs : Documentation {
let Category = DocCatFunction;
let Content = [{
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1430,6 +1430,13 @@
let Documentation = [LayoutVersionDocs];
}
+def Leaf : InheritableAttr {
+ let Spellings = [GCC<"leaf">];
+ let Subjects = SubjectList<[Function]>;
+ let Documentation = [Undocumented];
+ let SimpleHandler = 1;
+}
+
def LifetimeBound : DeclOrTypeAttr {
let Spellings = [Clang<"lifetimebound", 0>];
let Subjects = SubjectList<[ParmVar, ImplicitObjectParameter], ErrorDiag>;
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