New calling convention preserve_none

clang/include/clang-c/Index.h

@@ -2981,6 +2981,7 @@ enum CXCallingConv {
   CXCallingConv_SwiftAsync = 17,
   CXCallingConv_AArch64SVEPCS = 18,
   CXCallingConv_M68kRTD = 19,
+  CXCallingConv_PreserveNone = 20,
 
   CXCallingConv_Invalid = 100,
   CXCallingConv_Unexposed = 200

clang/include/clang/Basic/Attr.td

@@ -2868,6 +2868,12 @@ def M68kRTD: DeclOrTypeAttr {
   let Documentation = [M68kRTDDocs];
 }
 
+def PreserveNone : DeclOrTypeAttr, TargetSpecificAttr<TargetAnyX86> {
+  let Spellings = [Clang<"preserve_none">];
+  let Subjects = SubjectList<[FunctionLike]>;
+  let Documentation = [PreserveNoneDocs];
+}
+
 def Target : InheritableAttr {
   let Spellings = [GCC<"target">];
   let Args = [StringArgument<"featuresStr">];

clang/include/clang/Basic/AttrDocs.td

@@ -5494,6 +5494,23 @@ experimental at this time.
   }];
 }
 
+def PreserveNoneDocs : Documentation {
+  let Category = DocCatCallingConvs;
+  let Content = [{
+On X86-64 target, this attribute changes the calling convention of a function.
+The ``preserve_none`` calling convention tries to preserve as few general
+registers as possible. So all general registers are caller saved registers. It
+also uses more general registers to pass arguments. This attribute doesn't
+impact floating-point registers (XMMs/YMMs). Floating-point registers still
+follow the c calling convention.
+
+- Only RSP and RBP are preserved by callee.
+
+- Register RDI, RSI, RDX, RCX, R8, R9, R11, R12, R13, R14, R15 and RAX now can
+  be used to pass function arguments.
+  }];
+}
+
 def DeprecatedDocs : Documentation {
   let Category = DocCatDecl;
   let Content = [{

clang/include/clang/Basic/Specifiers.h

@@ -293,6 +293,7 @@ namespace clang {
     CC_AArch64SVEPCS, // __attribute__((aarch64_sve_pcs))
     CC_AMDGPUKernelCall, // __attribute__((amdgpu_kernel))
     CC_M68kRTD,       // __attribute__((m68k_rtd))
+    CC_PreserveNone,  // __attribute__((preserve_none))
   };
 
   /// Checks whether the given calling convention supports variadic

clang/lib/AST/ItaniumMangle.cpp

@@ -3442,6 +3442,7 @@ StringRef CXXNameMangler::getCallingConvQualifierName(CallingConv CC) {
   case CC_PreserveMost:
   case CC_PreserveAll:
   case CC_M68kRTD:
+  case CC_PreserveNone:
     // FIXME: we should be mangling all of the above.
     return "";
 

clang/lib/AST/Type.cpp

@@ -3409,6 +3409,7 @@ StringRef FunctionType::getNameForCallConv(CallingConv CC) {
   case CC_PreserveMost: return "preserve_most";
   case CC_PreserveAll: return "preserve_all";
   case CC_M68kRTD: return "m68k_rtd";
+  case CC_PreserveNone: return "preserve_none";
   }
 
   llvm_unreachable("Invalid calling convention.");
@@ -3889,6 +3890,7 @@ bool AttributedType::isCallingConv() const {
   case attr::PreserveMost:
   case attr::PreserveAll:
   case attr::M68kRTD:
+  case attr::PreserveNone:
     return true;
   }
   llvm_unreachable("invalid attr kind");

clang/lib/AST/TypePrinter.cpp

@@ -1047,6 +1047,9 @@ void TypePrinter::printFunctionAfter(const FunctionType::ExtInfo &Info,
     case CC_M68kRTD:
       OS << " __attribute__((m68k_rtd))";
       break;
+    case CC_PreserveNone:
+      OS << " __attribute__((preserve_none))";
+      break;
     }
   }
 
@@ -1885,6 +1888,9 @@ void TypePrinter::printAttributedAfter(const AttributedType *T,
   case attr::M68kRTD:
     OS << "m68k_rtd";
     break;
+  case attr::PreserveNone:
+    OS << "preserve_none";
+    break;
   case attr::NoDeref:
     OS << "noderef";
     break;

clang/lib/Basic/Targets/X86.h

@@ -772,6 +772,7 @@ class LLVM_LIBRARY_VISIBILITY X86_64TargetInfo : public X86TargetInfo {
     case CC_Win64:
     case CC_PreserveMost:
     case CC_PreserveAll:
+    case CC_PreserveNone:
     case CC_X86RegCall:
     case CC_OpenCLKernel:
       return CCCR_OK;
@@ -849,6 +850,7 @@ class LLVM_LIBRARY_VISIBILITY WindowsX86_64TargetInfo
     case CC_IntelOclBicc:
     case CC_PreserveMost:
     case CC_PreserveAll:
+    case CC_PreserveNone:
     case CC_X86_64SysV:
     case CC_Swift:
     case CC_SwiftAsync:

clang/lib/CodeGen/CGCall.cpp

@@ -73,6 +73,7 @@ unsigned CodeGenTypes::ClangCallConvToLLVMCallConv(CallingConv CC) {
   case CC_Swift: return llvm::CallingConv::Swift;
   case CC_SwiftAsync: return llvm::CallingConv::SwiftTail;
   case CC_M68kRTD: return llvm::CallingConv::M68k_RTD;
+  case CC_PreserveNone: return llvm::CallingConv::PreserveNone;
   }
 }
 
@@ -256,6 +257,9 @@ static CallingConv getCallingConventionForDecl(const ObjCMethodDecl *D,
   if (D->hasAttr<M68kRTDAttr>())
     return CC_M68kRTD;
 
+  if (D->hasAttr<PreserveNoneAttr>())
+    return CC_PreserveNone;
+
   return CC_C;
 }
 

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -1450,6 +1450,8 @@ static unsigned getDwarfCC(CallingConv CC) {
     return llvm::dwarf::DW_CC_LLVM_X86RegCall;
   case CC_M68kRTD:
     return llvm::dwarf::DW_CC_LLVM_M68kRTD;
+  case CC_PreserveNone:
+    return llvm::dwarf::DW_CC_LLVM_PreserveNone;
   }
   return 0;
 }

clang/lib/Sema/SemaDeclAttr.cpp

@@ -5219,6 +5219,9 @@ static void handleCallConvAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   case ParsedAttr::AT_M68kRTD:
     D->addAttr(::new (S.Context) M68kRTDAttr(S.Context, AL));
     return;
+  case ParsedAttr::AT_PreserveNone:
+    D->addAttr(::new (S.Context) PreserveNoneAttr(S.Context, AL));
+    return;
   default:
     llvm_unreachable("unexpected attribute kind");
   }
@@ -5425,6 +5428,9 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
   case ParsedAttr::AT_M68kRTD:
     CC = CC_M68kRTD;
     break;
+  case ParsedAttr::AT_PreserveNone:
+    CC = CC_PreserveNone;
+    break;
   default: llvm_unreachable("unexpected attribute kind");
   }
 
@@ -9355,6 +9361,7 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_AArch64SVEPcs:
   case ParsedAttr::AT_AMDGPUKernelCall:
   case ParsedAttr::AT_M68kRTD:
+  case ParsedAttr::AT_PreserveNone:
     handleCallConvAttr(S, D, AL);
     break;
   case ParsedAttr::AT_Suppress:

clang/lib/Sema/SemaType.cpp

@@ -137,7 +137,8 @@ static void diagnoseBadTypeAttribute(Sema &S, const ParsedAttr &attr,
   case ParsedAttr::AT_IntelOclBicc:                                            \
   case ParsedAttr::AT_PreserveMost:                                            \
   case ParsedAttr::AT_PreserveAll:                                             \
-  case ParsedAttr::AT_M68kRTD
+  case ParsedAttr::AT_M68kRTD:                                                 \
+  case ParsedAttr::AT_PreserveNone
 
 // Function type attributes.
 #define FUNCTION_TYPE_ATTRS_CASELIST                                           \
@@ -7852,6 +7853,8 @@ static Attr *getCCTypeAttr(ASTContext &Ctx, ParsedAttr &Attr) {
     return createSimpleAttr<PreserveAllAttr>(Ctx, Attr);
   case ParsedAttr::AT_M68kRTD:
     return createSimpleAttr<M68kRTDAttr>(Ctx, Attr);
+  case ParsedAttr::AT_PreserveNone:
+    return createSimpleAttr<PreserveNoneAttr>(Ctx, Attr);
   }
   llvm_unreachable("unexpected attribute kind!");
 }

clang/test/CodeGen/debug-info-cc.c

@@ -22,6 +22,7 @@
 //    CC_SwiftAsync,   // __attribute__((swiftasynccall))
 //    CC_PreserveMost, // __attribute__((preserve_most))
 //    CC_PreserveAll,  // __attribute__((preserve_all))
+//    CC_PreserveNone,  // __attribute__((preserve_none))
 //  };
 
 #ifdef __x86_64__
@@ -51,6 +52,12 @@ __attribute__((preserve_all)) int add_preserve_all(int a, int b) {
   return a+b;
 }
 
+// LINUX: !DISubprogram({{.*}}"add_preserve_none", {{.*}}type: ![[FTY:[0-9]+]]
+// LINUX: ![[FTY]] = !DISubroutineType({{.*}}cc: DW_CC_LLVM_PreserveNone,
+__attribute__((preserve_none)) int add_preserve_none(int a, int b) {
+  return a+b;
+}
+
 // LINUX: !DISubprogram({{.*}}"add_swiftcall", {{.*}}type: ![[FTY:[0-9]+]]
 // LINUX: ![[FTY]] = !DISubroutineType({{.*}}cc: DW_CC_LLVM_Swift,
 __attribute__((swiftcall)) int add_swiftcall(int a, int b) {

clang/test/CodeGen/preserve-call-conv.c

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm < %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm < %s | FileCheck %s --check-prefixes=CHECK,X86-LINUX
 // RUN: %clang_cc1 -triple arm64-unknown-unknown -emit-llvm < %s | FileCheck %s
 
 // RUN: %clang_cc1 -triple x86_64-unknown-windows-msvc -emit-llvm %s -o - | FileCheck %s
@@ -19,3 +19,9 @@ void boo(void) __attribute__((preserve_all)) {
   // CHECK-LABEL: define {{(dso_local )?}}preserve_allcc void @boo()
 }
 
+// Check that the preserve_none calling convention attribute at the source level
+// is lowered to the corresponding calling convention attrribute at the LLVM IR
+// level.
+void bar(void) __attribute__((preserve_none)) {
+  // X86-LINUX-LABEL: define {{(dso_local )?}}preserve_nonecc void @bar()
+}

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -161,6 +161,7 @@
 // CHECK-NEXT: PassObjectSize (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: PatchableFunctionEntry (SubjectMatchRule_function, SubjectMatchRule_objc_method)
 // CHECK-NEXT: Pointer (SubjectMatchRule_record_not_is_union)
+// CHECK-NEXT: PreserveNone (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: RandomizeLayout (SubjectMatchRule_record)
 // CHECK-NEXT: ReadOnlyPlacement (SubjectMatchRule_record)
 // CHECK-NEXT: ReleaseHandle (SubjectMatchRule_variable_is_parameter)

clang/test/Sema/no_callconv.cpp

@@ -15,6 +15,7 @@ void __attribute__((swiftasynccall)) funcKK() {} // expected-error {{'swiftasync
 void __attribute__((pascal)) funcG() {} // expected-error {{'pascal' calling convention is not supported for this target}}
 void __attribute__((preserve_most)) funcL() {} // expected-error {{'preserve_most' calling convention is not supported for this target}}
 void __attribute__((preserve_all)) funcM() {} // expected-error {{'preserve_all' calling convention is not supported for this target}}
+void __attribute__((preserve_none)) funcN() {} // expected-error {{'preserve_none' calling convention is not supported for this target}}
 void __attribute__((stdcall)) funcD() {} // expected-error {{'stdcall' calling convention is not supported for this target}}
 void __attribute__((fastcall)) funcE() {} // expected-error {{'fastcall' calling convention is not supported for this target}}
 void __attribute__((thiscall)) funcF() {} // expected-error {{'thiscall' calling convention is not supported for this target}}
@@ -30,6 +31,7 @@ void __attribute__((swiftcall)) funcK() {}
 void __attribute__((swiftasynccall)) funcKK() {}
 void __attribute__((preserve_most)) funcL() {}
 void __attribute__((preserve_all)) funcM() {}
+void __attribute__((preserve_none)) funcN() {}
 
 // Same function with different calling conventions. Error with a note pointing to the last decl.
 void __attribute__((preserve_all)) funcR(); // expected-note {{previous declaration is here}}

clang/test/Sema/preserve-none-call-conv.c

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 %s -fsyntax-only -triple x86_64-unknown-unknown -verify
+
+typedef void typedef_fun_t(int);
+
+void __attribute__((preserve_none)) boo(void *ptr) {
+}
+
+void __attribute__((preserve_none(1))) boo1(void *ptr) { // expected-error {{'preserve_none' attribute takes no arguments}}
+}
+
+void (__attribute__((preserve_none)) *pboo1)(void *) = boo;
+
+void (__attribute__((cdecl)) *pboo2)(void *) = boo; // expected-error {{incompatible function pointer types initializing 'void (*)(void *) __attribute__((cdecl))' with an expression of type 'void (void *) __attribute__((preserve_none))'}}
+void (*pboo3)(void *) = boo; // expected-error {{incompatible function pointer types initializing 'void (*)(void *)' with an expression of type 'void (void *) __attribute__((preserve_none))'}}
+
+typedef_fun_t typedef_fun_boo; // expected-note {{previous declaration is here}}
+void __attribute__((preserve_none)) typedef_fun_boo(int x) { } // expected-error {{function declared 'preserve_none' here was previously declared without calling convention}}
+
+struct type_test_boo {} __attribute__((preserve_none));  // expected-warning {{'preserve_none' attribute only applies to functions and function pointers}}

clang/tools/libclang/CXType.cpp

@@ -679,6 +679,7 @@ CXCallingConv clang_getFunctionTypeCallingConv(CXType X) {
       TCALLINGCONV(PreserveMost);
       TCALLINGCONV(PreserveAll);
       TCALLINGCONV(M68kRTD);
+      TCALLINGCONV(PreserveNone);
     case CC_SpirFunction: return CXCallingConv_Unexposed;
     case CC_AMDGPUKernelCall: return CXCallingConv_Unexposed;
     case CC_OpenCLKernel: return CXCallingConv_Unexposed;

llvm/docs/LangRef.rst

@@ -416,6 +416,13 @@ added in the future:
     This calling convention, like the `PreserveMost` calling convention, will be
     used by a future version of the ObjectiveC runtime and should be considered
     experimental at this time.
+"``preserve_nonecc``" - The `PreserveNone` calling convention
+    This calling convention doesn't preserve any general registers. So all
+    general registers are caller saved registers. It also uses all general
+    registers to pass arguments. This attribute doesn't impact non-general
+    purpose registers (e.g. floating point registers, on X86 XMMs/YMMs).
+    Non-general purpose registers still follow the standard c calling
+    convention. Currently it is for x86_64 only.
 "``cxx_fast_tlscc``" - The `CXX_FAST_TLS` calling convention for access functions
     Clang generates an access function to access C++-style TLS. The access
     function generally has an entry block, an exit block and an initialization

llvm/include/llvm/AsmParser/LLToken.h

@@ -160,6 +160,7 @@ enum Kind {
   kw_swifttailcc,
   kw_preserve_mostcc,
   kw_preserve_allcc,
+  kw_preserve_nonecc,
   kw_ghccc,
   kw_x86_intrcc,
   kw_hhvmcc,

llvm/include/llvm/BinaryFormat/Dwarf.def

@@ -1038,6 +1038,7 @@ HANDLE_DW_CC(0xc9, LLVM_PreserveMost)
 HANDLE_DW_CC(0xca, LLVM_PreserveAll)
 HANDLE_DW_CC(0xcb, LLVM_X86RegCall)
 HANDLE_DW_CC(0xcc, LLVM_M68kRTD)
+HANDLE_DW_CC(0xcd, LLVM_PreserveNone)
 // From GCC source code (include/dwarf2.h): This DW_CC_ value is not currently
 // generated by any toolchain.  It is used internally to GDB to indicate OpenCL
 // C functions that have been compiled with the IBM XL C for OpenCL compiler and

llvm/include/llvm/IR/CallingConv.h

@@ -86,6 +86,9 @@ namespace CallingConv {
     /// their stack.
     SwiftTail = 20,
 
+    /// Used for runtime calls that preserves none general registers.
+    PreserveNone = 21,
+
     /// This is the start of the target-specific calling conventions, e.g.
     /// fastcall and thiscall on X86.
     FirstTargetCC = 64,

llvm/lib/AsmParser/LLLexer.cpp

@@ -617,6 +617,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(anyregcc);
   KEYWORD(preserve_mostcc);
   KEYWORD(preserve_allcc);
+  KEYWORD(preserve_nonecc);
   KEYWORD(ghccc);
   KEYWORD(x86_intrcc);
   KEYWORD(hhvmcc);

llvm/lib/AsmParser/LLParser.cpp

@@ -1985,6 +1985,7 @@ void LLParser::parseOptionalDLLStorageClass(unsigned &Res) {
 ///   ::= 'anyregcc'
 ///   ::= 'preserve_mostcc'
 ///   ::= 'preserve_allcc'
+///   ::= 'preserve_nonecc'
 ///   ::= 'ghccc'
 ///   ::= 'swiftcc'
 ///   ::= 'swifttailcc'
@@ -2045,6 +2046,7 @@ bool LLParser::parseOptionalCallingConv(unsigned &CC) {
   case lltok::kw_anyregcc:       CC = CallingConv::AnyReg; break;
   case lltok::kw_preserve_mostcc:CC = CallingConv::PreserveMost; break;
   case lltok::kw_preserve_allcc: CC = CallingConv::PreserveAll; break;
+  case lltok::kw_preserve_nonecc:CC = CallingConv::PreserveNone; break;
   case lltok::kw_ghccc:          CC = CallingConv::GHC; break;
   case lltok::kw_swiftcc:        CC = CallingConv::Swift; break;
   case lltok::kw_swifttailcc:    CC = CallingConv::SwiftTail; break;

llvm/lib/DebugInfo/DWARF/DWARFTypePrinter.cpp

@@ -617,6 +617,9 @@ void DWARFTypePrinter::appendSubroutineNameAfter(
     case CallingConvention::DW_CC_LLVM_PreserveAll:
       OS << " __attribute__((preserve_all))";
       break;
+    case CallingConvention::DW_CC_LLVM_PreserveNone:
+      OS << " __attribute__((preserve_none))";
+      break;
     case CallingConvention::DW_CC_LLVM_X86RegCall:
       OS << " __attribute__((regcall))";
       break;

llvm/lib/IR/AsmWriter.cpp

@@ -304,6 +304,7 @@ static void PrintCallingConv(unsigned cc, raw_ostream &Out) {
   case CallingConv::AnyReg:        Out << "anyregcc"; break;
   case CallingConv::PreserveMost:  Out << "preserve_mostcc"; break;
   case CallingConv::PreserveAll:   Out << "preserve_allcc"; break;
+  case CallingConv::PreserveNone:  Out << "preserve_nonecc"; break;
   case CallingConv::CXX_FAST_TLS:  Out << "cxx_fast_tlscc"; break;
   case CallingConv::GHC:           Out << "ghccc"; break;
   case CallingConv::Tail:          Out << "tailcc"; break;

llvm/lib/Target/X86/X86CallingConv.td

@@ -1056,6 +1056,23 @@ def CC_Intel_OCL_BI : CallingConv<[
   CCDelegateTo<CC_X86_32_C>
 ]>;
 
+def CC_X86_64_Preserve_None : CallingConv<[
+  // We don't preserve general registers, so all of them can be used to pass
+  // arguments except
+  //   - RBP        frame pointer
+  //   - R10        'nest' parameter
+  //   - RBX        base pointer
+  //   - R16 - R31  these are not available everywhere
+  CCIfType<[i32], CCAssignToReg<[EDI, ESI, EDX, ECX, R8D, R9D,
+	                         R11D, R12D, R13D, R14D, R15D, EAX]>>,
+
+  CCIfType<[i64], CCAssignToReg<[RDI, RSI, RDX, RCX, R8, R9,
+                                 R11, R12, R13, R14, R15, RAX]>>,
+
+  // Otherwise it's the same as the regular C calling convention.
+  CCDelegateTo<CC_X86_64_C>
+]>;
+
 //===----------------------------------------------------------------------===//
 // X86 Root Argument Calling Conventions
 //===----------------------------------------------------------------------===//
@@ -1095,6 +1112,7 @@ def CC_X86_64 : CallingConv<[
   CCIfCC<"CallingConv::X86_RegCall",
     CCIfSubtarget<"isTargetWin64()", CCDelegateTo<CC_X86_Win64_RegCall>>>,
   CCIfCC<"CallingConv::X86_RegCall", CCDelegateTo<CC_X86_SysV64_RegCall>>,
+  CCIfCC<"CallingConv::PreserveNone", CCDelegateTo<CC_X86_64_Preserve_None>>,
   CCIfCC<"CallingConv::X86_INTR", CCCustom<"CC_X86_Intr">>,
 
   // Mingw64 and native Win64 use Win64 CC
@@ -1184,6 +1202,7 @@ def CSR_64_AllRegs_AVX512 : CalleeSavedRegs<(sub (add CSR_64_MostRegs, RAX,
                                                       (sequence "ZMM%u", 0, 31),
                                                       (sequence "K%u", 0, 7)),
                                                  (sequence "XMM%u", 0, 15))>;
+def CSR_64_NoneRegs    : CalleeSavedRegs<(add RBP)>;
 
 // Standard C + YMM6-15
 def CSR_Win64_Intel_OCL_BI_AVX : CalleeSavedRegs<(add RBX, RBP, RDI, RSI, R12,