[Clang] Add __builtin_stack_address

clang/docs/LanguageExtensions.rst

@@ -4248,6 +4248,39 @@ 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.
+
+**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

@@ -111,6 +111,10 @@ 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.
+
 C2y Feature Support
 ^^^^^^^^^^^^^^^^^^^
 

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

@@ -4700,6 +4700,10 @@ 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/test/CodeGen/builtin-stackaddress.c

@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
+
+// CHECK-LABEL: define {{[^@]+}} @a()
+// CHECK: call {{[^@]+}} @llvm.stackaddress.p0()
+void *a() {
+  return __builtin_stack_address();
+}

clang/test/CodeGenCXX/builtin-stackaddress.cpp

@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm %s -o - | llvm-cxxfilt | FileCheck %s --check-prefixes=COMMON,NO-OPT
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm %s -O3 -o - | llvm-cxxfilt | FileCheck %s --check-prefixes=COMMON,OPT
+
+struct S {
+  void *a();
+};
+
+// COMMON-LABEL: @S::a()
+// COMMON: call ptr @llvm.stackaddress.p0()
+void *S::a() {
+  return __builtin_stack_address();
+}
+
+// COMMON-LABEL: define {{[^@]+}} @two()
+void *two() {
+
+  // The compiler is allowed to inline a function calling `__builtin_stack_address`.
+  //
+  // OPT-NOT: define {{[^@]+}} @"two()::$_0::operator()() const"
+  // OPT: call {{[^@]+}} @llvm.stackaddress.p0()
+  //
+  // NO-OPT-DAG: define {{[^@]+}} @"two()::$_0::operator()() const"
+  // NO-OPT-DAG: call {{[^@]+}} @"two()::$_0::operator()() const"
+  auto l = []() { return __builtin_stack_address(); };
+  return l();
+}

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

@@ -14389,6 +14389,35 @@ Semantics:
 
 Note this intrinsic is only verified on AArch64 and ARM.
 
+'``llvm.stackaddress``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare ptr @llvm.stackaddress.p0()
+
+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.
+
 '``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

@@ -1012,6 +1012,7 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
   case ISD::INTRINSIC_WO_CHAIN:
   case ISD::INTRINSIC_VOID:
   case ISD::STACKSAVE:
+  case ISD::STACKADDRESS:
     Action = TLI.getOperationAction(Node->getOpcode(), MVT::Other);
     break;
   case ISD::GET_DYNAMIC_AREA_OFFSET:
@@ -3680,6 +3681,7 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     Results.push_back(Tmp1);
     break;
   }
+  case ISD::STACKADDRESS:
   case ISD::STACKSAVE:
     // Expand to CopyFromReg if the target set
     // StackPointerRegisterToSaveRestore.
@@ -3690,6 +3692,13 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     } else {
       Results.push_back(DAG.getUNDEF(Node->getValueType(0)));
       Results.push_back(Node->getOperand(0));
+
+      const char *IntrinsicName = Node->getOpcode() == ISD::STACKADDRESS
+                                      ? "llvm.stackaddress"
+                                      : "llvm.stacksave";
+      DAG.getContext()->diagnose(DiagnosticInfoLegalizationFailure(
+          Twine(IntrinsicName) + " is not supported on this target.",
+          DAG.getMachineFunction().getFunction(), dl.getDebugLoc()));
     }
     break;
   case ISD::STACKRESTORE:

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -7326,10 +7326,13 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
     setValue(&I, DAG.getNode(ISD::UCMP, sdl, DestVT, Op1, Op2));
     break;
   }
+  case Intrinsic::stackaddress:
   case Intrinsic::stacksave: {
+    unsigned SDOpcode = Intrinsic == Intrinsic::stackaddress ? ISD::STACKADDRESS
+                                                             : ISD::STACKSAVE;
     SDValue Op = getRoot();
     EVT VT = TLI.getValueType(DAG.getDataLayout(), I.getType());
-    Res = DAG.getNode(ISD::STACKSAVE, sdl, DAG.getVTList(VT, MVT::Other), Op);
+    Res = DAG.getNode(SDOpcode, sdl, DAG.getVTList(VT, MVT::Other), Op);
     setValue(&I, Res);
     DAG.setRoot(Res.getValue(1));
     return;

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/CodeGen/TargetLoweringBase.cpp

@@ -956,6 +956,10 @@ void TargetLoweringBase::initActions() {
   // This one by default will call __clear_cache unless the target
   // wants something different.
   setOperationAction(ISD::CLEAR_CACHE, MVT::Other, LibCall);
+
+  // By default, STACKADDRESS nodes are expanded like STACKSAVE nodes.
+  // On SPARC targets, custom lowering is required.
+  setOperationAction(ISD::STACKADDRESS, MVT::Other, Expand);
 }
 
 MVT TargetLoweringBase::getScalarShiftAmountTy(const DataLayout &DL,

llvm/lib/Target/Sparc/SparcISelLowering.cpp

@@ -1861,6 +1861,7 @@ SparcTargetLowering::SparcTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::STACKSAVE         , MVT::Other, Expand);
   setOperationAction(ISD::STACKRESTORE      , MVT::Other, Expand);
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i32  , Custom);
+  setOperationAction(ISD::STACKADDRESS, MVT::Other, Custom);
 
   setStackPointerRegisterToSaveRestore(SP::O6);
 
@@ -2720,6 +2721,28 @@ static SDValue LowerVAARG(SDValue Op, SelectionDAG &DAG) {
       Align(std::min(PtrVT.getFixedSizeInBits(), VT.getFixedSizeInBits()) / 8));
 }
 
+static SDValue LowerSTACKADDRESS(SDValue Op, SelectionDAG &DAG,
+                                 const SparcSubtarget *Subtarget) {
+  SDValue Chain = Op.getOperand(0);
+  EVT VT = Op->getValueType(0);
+  SDLoc DL(Op);
+
+  unsigned SPReg = SP::O6;
+  SDValue SP = DAG.getCopyFromReg(Chain, DL, SPReg, VT);
+
+  // Unbias the stack pointer register.
+  unsigned OffsetToStackStart = Subtarget->getStackPointerBias();
+  // Move past the register save area: 8 in registers + 8 local registers.
+  OffsetToStackStart += 16 * (Subtarget->is64Bit() ? 8 : 4);
+  // Move past the struct return address slot (4 bytes) on SPARC 32-bit.
+  if (!Subtarget->is64Bit())
+    OffsetToStackStart += 4;
+
+  SDValue StackAddr = DAG.getNode(ISD::ADD, DL, VT, SP,
+                                  DAG.getConstant(OffsetToStackStart, DL, VT));
+  return DAG.getMergeValues({StackAddr, Chain}, DL);
+}
+
 static SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG,
                                        const SparcSubtarget *Subtarget) {
   SDValue Chain = Op.getOperand(0);
@@ -3117,6 +3140,8 @@ LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::VAARG:              return LowerVAARG(Op, DAG);
   case ISD::DYNAMIC_STACKALLOC: return LowerDYNAMIC_STACKALLOC(Op, DAG,
                                                                Subtarget);
+  case ISD::STACKADDRESS:
+    return LowerSTACKADDRESS(Op, DAG, Subtarget);
 
   case ISD::LOAD:               return LowerLOAD(Op, DAG);
   case ISD::STORE:              return LowerSTORE(Op, DAG);

llvm/test/CodeGen/AArch64/stackaddress.ll

@@ -0,0 +1,10 @@
+; RUN: llc < %s -mtriple=aarch64 | FileCheck %s
+
+declare ptr @llvm.stackaddress.p0()
+
+define ptr @test() {
+; CHECK: mov x0, sp
+; CHECK: ret
+  %sp = call ptr @llvm.stackaddress.p0()
+  ret ptr %sp
+}

llvm/test/CodeGen/ARM/stackaddress.ll

@@ -0,0 +1,10 @@
+; RUN: llc < %s -mtriple=armv7 | FileCheck %s
+
+declare ptr @llvm.stackaddress.p0()
+
+define ptr @test() {
+; CHECK: mov r0, sp
+; CHECK: bx  lr
+  %sp = call ptr @llvm.stackaddress.p0()
+  ret ptr %sp
+}

llvm/test/CodeGen/NVPTX/stackaddress.ll

@@ -0,0 +1,9 @@
+; RUN: not llc < %s -mtriple nvptx 2>&1 | FileCheck %s
+
+declare ptr @llvm.stackaddress.p0()
+
+define ptr @test() {
+; CHECK: error: <unknown>:0:0: llvm.stackaddress is not supported on this target.
+  %sp = call ptr @llvm.stackaddress.p0()
+  ret ptr %sp
+}

llvm/test/CodeGen/SPARC/stackaddress.ll

@@ -0,0 +1,16 @@
+; RUN: llc < %s -mtriple=sparc   | FileCheck --check-prefix=sparc32 %s
+; RUN: llc < %s -mtriple=sparcv9 | FileCheck --check-prefix=sparc64 %s
+
+declare ptr @llvm.stackaddress.p0()
+
+define ptr @test() {
+; sparc32: save %sp, -96, %sp
+; sparc32: ret
+; sparc32: restore %sp, 68, %o0
+;
+; sparc64: save %sp, -128, %sp
+; sparc64: ret
+; sparc64: restore %sp, 2175, %o0
+  %sp = call ptr @llvm.stackaddress.p0()
+  ret ptr %sp
+}

llvm/test/CodeGen/X86/stackaddress.ll

@@ -0,0 +1,14 @@
+; RUN: llc < %s -mtriple=x86_64-linux-gnu -o - | FileCheck --check-prefix=x86_64 %s
+; RUN: llc < %s -mtriple=i386-linux-gnu -o -   | FileCheck --check-prefix=i386   %s
+
+declare ptr @llvm.stackaddress.p0()
+
+define ptr @test() {
+; x86_64: movq %rsp, %rax
+; x86_64: retq
+
+; i386: movl %esp, %eax
+; i386: retl
+  %sp = call ptr @llvm.stackaddress.p0()
+  ret ptr %sp
+}