[Clang] Add __builtin_stack_address

clang/docs/LanguageExtensions.rst

@@ -4189,6 +4189,39 @@ assignment can happen automatically.
 to a variable, have its address taken, or passed into or returned from a
 function, because doing so violates bounds safety conventions.
 
+.. _builtin_stack_address-doc:
+
+``__builtin_stack_address``
+---------------------------
+
+``__builtin_stack_address`` returns the address that separates the current
+function's (i.e. the one calling the builtin) stack space and the region of the
+stack that may be modified by called functions. The semantics match those of GCC's builtin of the same name.
+
+**Note:** Support for this builtin is currently limited to the following architectures: x86_64, x86.
+
+**Syntax**:
+
+.. code-block:: c++
+
+  void *__builtin_stack_address()
+
+**Example**:
+
+.. code-block:: c++
+
+  void *sp = __builtin_stack_address();
+
+**Description**:
+
+The address returned by ``__builtin_stack_address`` identifies the starting
+address of the stack region that may be used by called functions.
+
+On some architectures (e.g. x86), it's sufficient to return the value in the stack pointer register
+directly. On others (e.g. SPARCv9), adjustments are required to the value of the stack pointer
+register. ``__builtin_stack_address`` performs the necessary adjustments and returns the correct
+boundary address.
+
 Multiprecision Arithmetic Builtins
 ----------------------------------
 

clang/docs/ReleaseNotes.rst

@@ -172,6 +172,8 @@ Resolutions to C++ Defect Reports
 C Language Changes
 ------------------
 
+- Clang now supports the :ref:`__builtin_stack_address <builtin_stack_address-doc>` () builtin.
+  The semantics match those of GCC's builtin with the same name.
 - Clang now allows an ``inline`` specifier on a typedef declaration of a
   function type in Microsoft compatibility mode. #GH124869
 - Clang now allows ``restrict`` qualifier for array types with pointer elements (#GH92847).

clang/include/clang/Basic/Builtins.td

@@ -917,6 +917,12 @@ def FrameAddress : Builtin {
   let Prototype = "void*(_Constant unsigned int)";
 }
 
+def StackAddress : Builtin {
+  let Spellings = ["__builtin_stack_address"];
+  let Attributes = [NoThrow];
+  let Prototype = "void*()";
+}
+
 def ClearCache : Builtin {
   let Spellings = ["__builtin___clear_cache"];
   let Attributes = [NoThrow];

clang/lib/CodeGen/CGBuiltin.cpp

@@ -4673,6 +4673,10 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     Function *F = CGM.getIntrinsic(Intrinsic::frameaddress, AllocaInt8PtrTy);
     return RValue::get(Builder.CreateCall(F, Depth));
   }
+  case Builtin::BI__builtin_stack_address: {
+    return RValue::get(Builder.CreateCall(
+        CGM.getIntrinsic(Intrinsic::stackaddress, AllocaInt8PtrTy)));
+  }
   case Builtin::BI__builtin_extract_return_addr: {
     Value *Address = EmitScalarExpr(E->getArg(0));
     Value *Result = getTargetHooks().decodeReturnAddress(*this, Address);

clang/lib/Sema/SemaChecking.cpp

@@ -2958,6 +2958,15 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
     break;
   }
 
+  case Builtin::BI__builtin_stack_address: {
+    if (CheckBuiltinTargetInSupported(
+            *this, TheCall,
+            /*SupportedArchs=*/{llvm::Triple::x86_64, llvm::Triple::x86})) {
+      return ExprError();
+    }
+    break;
+  }
+
   case Builtin::BI__builtin_nondeterministic_value: {
     if (BuiltinNonDeterministicValue(TheCall))
       return ExprError();

clang/test/CodeGen/builtin-stackaddress.c

@@ -0,0 +1,14 @@
+// RUN: %clang -target x86_64 -S -emit-llvm %s -o - | FileCheck %s --check-prefix=llvm
+// RUN: %clang -target x86_64 -S %s -o - | FileCheck %s --check-prefix=x64
+
+extern void f(int, int, int, long, long, long, long, long, long, long, long);
+
+// llvm-LABEL: define {{[^@]+}} @a()
+// llvm:       call   {{[^@]+}} @llvm.stackaddress.p0()
+//
+// x64-LABEL: a:
+// x64:       movq  %rsp, %rax
+void *a() {
+  f(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
+  return __builtin_stack_address();
+}

clang/test/CodeGenCXX/builtin-stackaddress.cpp

@@ -0,0 +1,36 @@
+// RUN: %clang -target x86_64 -S -emit-llvm %s -o - | llvm-cxxfilt | FileCheck %s --check-prefix=llvm
+// RUN: %clang -target x86_64 -S %s -o - | llvm-cxxfilt | FileCheck %s --check-prefix=x64
+
+extern void f(int, int, int, long, long, long, long, long, long, long, long);
+
+struct S {
+  void *a();
+};
+
+// llvm-LABEL: define {{[^@]+}} @S::a()
+// llvm:       call   {{[^@]+}} @llvm.stackaddress.p0()
+//
+// x64-LABEL: S::a():
+// x64:       movq  %rsp, %rax
+void *S::a() {
+  void *p = __builtin_stack_address();
+  f(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
+  return p;
+}
+
+// llvm-LABEL: define {{[^@]+}} @two()
+// llvm:       call   {{[^@]+}} @"two()::$_0::operator()() const"
+//
+// llvm-LABEL: define {{[^@]+}} @"two()::$_0::operator()() const"
+// llvm:       call   {{[^@]+}} @llvm.stackaddress.p0()
+//
+// x64-LABEL: two()::$_0::operator()() const:
+// x64:       movq  %rsp, %rax
+void *two() {
+  auto l = []() {
+    void *p = __builtin_stack_address();
+    f(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
+    return p;
+  };
+  return l();
+}

clang/test/Sema/builtin-stackaddress-target-support.c

@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -verify %s -triple x86_64-unknown-unknown -DTEST_x64
+// RUN: %clang_cc1 -verify %s -triple i386-unknown-unknown -DTEST_x86
+// RUN: %clang_cc1 -verify %s -triple riscv32-unknown-unknown -DTEST_riscv32
+// RUN: %clang_cc1 -verify %s -triple riscv64-unknown-unknown -DTEST_riscv64
+// RUN: %clang_cc1 -verify %s -triple aarch64-unknown-unknown -DTEST_aarch64
+
+#if defined(TEST_x64) || defined(TEST_x86)
+// expected-no-diagnostics
+void *a() {
+return __builtin_stack_address();
+}
+#else
+void *a() {
+return __builtin_stack_address(); // expected-error {{builtin is not supported on this target}}
+}
+#endif

clang/test/Sema/builtin-stackaddress.c

@@ -36,3 +36,8 @@ void* h(unsigned x) {
 // expected-error@+1 {{argument value 1048575 is outside the valid range [0, 65535]}}
 return __builtin_frame_address(0xFFFFF);
 }
+
+void *i() {
+// expected-error@+1 {{too many arguments to function call, expected 0, have 1}}
+return __builtin_stack_address(0);
+}

llvm/docs/LangRef.rst

@@ -14295,6 +14295,36 @@ Semantics:
 
 Note this intrinsic is only verified on AArch64 and ARM.
 
+'``llvm.stackaddress``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare ptr @llvm.stackaddress()
+
+Overview:
+"""""""""
+
+The '``llvm.stackaddress``' instrinsic returns the starting address of the stack region that may be
+used by called functions.
+
+Semantics:
+""""""""""
+
+This intrinsic returns the *logical* value of the stack pointer register, that is, the address
+separating the stack space of the current function from the stack space that may be modified by
+called functions.
+
+On certain targets (e.g. x86), the logical and actual (or physical) values of the stack pointer
+register are the same. However, on other architectures (e.g. SPARCv9), the logical value of the
+stack pointer register may differ from the physical value. '``llvm.stackaddress``' handles this
+discrepancy and returns the correct boundary address.
+
+**Note**: This intrinsic is currently only implemented for x86 and x86-64.
+
 '``llvm.frameaddress``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

llvm/include/llvm/CodeGen/ISDOpcodes.h

@@ -121,6 +121,11 @@ enum NodeType {
   /// function calling this intrinsic.
   SPONENTRY,
 
+  /// STACKADDRESS - Represents the llvm.stackaddress intrinsic. Takes no
+  /// argument and returns the starting address of the stack region that may be
+  /// used by called functions.
+  STACKADDRESS,
+
   /// LOCAL_RECOVER - Represents the llvm.localrecover intrinsic.
   /// Materializes the offset from the local object pointer of another
   /// function to a particular local object passed to llvm.localescape. The

llvm/include/llvm/IR/Intrinsics.td

@@ -853,6 +853,7 @@ def int_addressofreturnaddress : DefaultAttrsIntrinsic<[llvm_anyptr_ty], [], [In
 def int_frameaddress : DefaultAttrsIntrinsic<[llvm_anyptr_ty], [llvm_i32_ty],
                                  [IntrNoMem, ImmArg<ArgIndex<0>>]>;
 def int_sponentry  : DefaultAttrsIntrinsic<[llvm_anyptr_ty], [], [IntrNoMem]>;
+def int_stackaddress : DefaultAttrsIntrinsic<[llvm_anyptr_ty], [], []>;
 def int_read_register  : DefaultAttrsIntrinsic<[llvm_anyint_ty], [llvm_metadata_ty],
                                    [IntrReadMem], "llvm.read_register">;
 def int_write_register : Intrinsic<[], [llvm_metadata_ty, llvm_anyint_ty],

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -1120,6 +1120,7 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
   case ISD::ADJUST_TRAMPOLINE:
   case ISD::FRAMEADDR:
   case ISD::RETURNADDR:
+  case ISD::STACKADDRESS:
   case ISD::ADDROFRETURNADDR:
   case ISD::SPONENTRY:
     // These operations lie about being legal: when they claim to be legal,

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -6522,6 +6522,12 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
                              TLI.getFrameIndexTy(DAG.getDataLayout()),
                              getValue(I.getArgOperand(0))));
     return;
+  case Intrinsic::stackaddress: {
+    setValue(&I,
+             DAG.getNode(ISD::STACKADDRESS, sdl,
+                         TLI.getValueType(DAG.getDataLayout(), I.getType())));
+    return;
+  }
   case Intrinsic::read_volatile_register:
   case Intrinsic::read_register: {
     Value *Reg = I.getArgOperand(0);

llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp

@@ -148,6 +148,7 @@ std::string SDNode::getOperationName(const SelectionDAG *G) const {
   case ISD::ADDROFRETURNADDR:           return "ADDROFRETURNADDR";
   case ISD::FRAMEADDR:                  return "FRAMEADDR";
   case ISD::SPONENTRY:                  return "SPONENTRY";
+  case ISD::STACKADDRESS:               return "STACKADDRESS";
   case ISD::LOCAL_RECOVER:              return "LOCAL_RECOVER";
   case ISD::READ_REGISTER:              return "READ_REGISTER";
   case ISD::WRITE_REGISTER:             return "WRITE_REGISTER";

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -28274,6 +28274,14 @@ SDValue X86TargetLowering::LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const {
   return FrameAddr;
 }
 
+SDValue X86TargetLowering::LowerSTACKADDRESS(SDValue Op,
+                                             SelectionDAG &DAG) const {
+  SDLoc dl(Op);
+  return DAG.getCopyFromReg(DAG.getEntryNode(), dl,
+                            Subtarget.getRegisterInfo()->getStackRegister(),
+                            Op->getValueType(0));
+}
+
 // FIXME? Maybe this could be a TableGen attribute on some registers and
 // this table could be generated automatically from RegInfo.
 Register X86TargetLowering::getRegisterByName(const char* RegName, LLT VT,
@@ -33637,6 +33645,7 @@ SDValue X86TargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::RETURNADDR:         return LowerRETURNADDR(Op, DAG);
   case ISD::ADDROFRETURNADDR:   return LowerADDROFRETURNADDR(Op, DAG);
   case ISD::FRAMEADDR:          return LowerFRAMEADDR(Op, DAG);
+  case ISD::STACKADDRESS:       return LowerSTACKADDRESS(Op, DAG);
   case ISD::FRAME_TO_ARGS_OFFSET:
                                 return LowerFRAME_TO_ARGS_OFFSET(Op, DAG);
   case ISD::DYNAMIC_STACKALLOC: return LowerDYNAMIC_STACKALLOC(Op, DAG);

llvm/lib/Target/X86/X86ISelLowering.h

@@ -1771,6 +1771,7 @@ namespace llvm {
     SDValue LowerRETURNADDR(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerADDROFRETURNADDR(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
+    SDValue LowerSTACKADDRESS(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerFRAME_TO_ARGS_OFFSET(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerEH_RETURN(SDValue Op, SelectionDAG &DAG) const;
     SDValue lowerEH_SJLJ_SETJMP(SDValue Op, SelectionDAG &DAG) const;