Index: docs/LangRef.rst =================================================================== --- docs/LangRef.rst +++ docs/LangRef.rst @@ -6804,6 +6804,49 @@ other aggressive transformations, so the value returned may not be that of the obvious source-language caller. +.. _int_read_register: +.. _int_write_register: + +'``llvm.read_register``' and '``llvm.write_register``' Intrinsics +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Syntax: +""""""" + +:: + + declare i32 @llvm.read_register.i32(metadata) + declare i64 @llvm.read_register.i64(metadata) + declare void @llvm.write_register.i32(metadata, i32 @value) + declare void @llvm.write_register.i64(metadata, i64 @value) + !0 = metadata !{metadata !"sp\00"} + +Overview: +""""""""" + +The '``llvm.read_register``' and '``llvm.write_register``' intrinsics +provides access to the named register. The register must be valid on +the architecture being compiled to. The type needs to be compatible +with the register being read. + +Semantics: +"""""""""" + +The '``llvm.read_register``' intrinsic returns the current value of the +register, where possible. The '``llvm.write_register``' intrinsic sets +the current value of the register, where possible. + +This is useful to implement named register global variables that need +to always be mapped to a specific register, as is common practice on +bare-metal programs including OS kernels. + +The compiler doesn't check for register availability or use of the used +register in surrounding code, including inline assembly. + +Warning: There is no register reservation at the moment, and so far it +only works with the stack pointer on selected architectures (ARM, ARM64, +x86_64 and AArch64). + .. _int_stacksave: '``llvm.stacksave``' Intrinsic Index: include/llvm/CodeGen/ISDOpcodes.h =================================================================== --- include/llvm/CodeGen/ISDOpcodes.h +++ include/llvm/CodeGen/ISDOpcodes.h @@ -72,6 +72,11 @@ /// the parent's frame or return address, and so on. FRAMEADDR, RETURNADDR, + /// READ_REGISTER, WRITE_REGISTER - This node represents llvm.register on + /// the DAG, which implements the named register global variables extension. + READ_REGISTER, + WRITE_REGISTER, + /// FRAME_TO_ARGS_OFFSET - This node represents offset from frame pointer to /// first (possible) on-stack argument. This is needed for correct stack /// adjustment during unwind. Index: include/llvm/CodeGen/SelectionDAGISel.h =================================================================== --- include/llvm/CodeGen/SelectionDAGISel.h +++ include/llvm/CodeGen/SelectionDAGISel.h @@ -242,6 +242,8 @@ // Calls to these functions are generated by tblgen. SDNode *Select_INLINEASM(SDNode *N); + SDNode *Select_READ_REGISTER(SDNode *N); + SDNode *Select_WRITE_REGISTER(SDNode *N); SDNode *Select_UNDEF(SDNode *N); void CannotYetSelect(SDNode *N); Index: include/llvm/IR/Intrinsics.td =================================================================== --- include/llvm/IR/Intrinsics.td +++ include/llvm/IR/Intrinsics.td @@ -250,6 +250,10 @@ // def int_returnaddress : Intrinsic<[llvm_ptr_ty], [llvm_i32_ty], [IntrNoMem]>; def int_frameaddress : Intrinsic<[llvm_ptr_ty], [llvm_i32_ty], [IntrNoMem]>; +def int_read_register : Intrinsic<[llvm_anyint_ty], [llvm_metadata_ty], + [IntrNoMem], "llvm.read_register">; +def int_write_register : Intrinsic<[], [llvm_metadata_ty, llvm_anyint_ty], + [IntrNoMem], "llvm.write_register">; // Note: we treat stacksave/stackrestore as writemem because we don't otherwise // model their dependencies on allocas. Index: include/llvm/Target/TargetLowering.h =================================================================== --- include/llvm/Target/TargetLowering.h +++ include/llvm/Target/TargetLowering.h @@ -2214,6 +2214,13 @@ return "__clear_cache"; } + /// Return the register ID of the name passed in. Used by named register + /// global variables extension. There is no target-independent behaviour + /// so the default action is to bail. + virtual unsigned getRegisterByName(const char* RegName) const { + report_fatal_error("Named registers not implemented for this target"); + } + /// Return the type that should be used to zero or sign extend a /// zeroext/signext integer argument or return value. FIXME: Most C calling /// convention requires the return type to be promoted, but this is not true Index: lib/CodeGen/SelectionDAG/LegalizeDAG.cpp =================================================================== --- lib/CodeGen/SelectionDAG/LegalizeDAG.cpp +++ lib/CodeGen/SelectionDAG/LegalizeDAG.cpp @@ -1265,6 +1265,13 @@ if (Action == TargetLowering::Legal) Action = TargetLowering::Custom; break; + case ISD::READ_REGISTER: + case ISD::WRITE_REGISTER: + // Named register is legal in the DAG, but blocked by register name + // selection if not implemented by target (to chose the correct register) + // They'll be converted to Copy(To/From)Reg. + Action = TargetLowering::Legal; + break; case ISD::DEBUGTRAP: Action = TLI.getOperationAction(Node->getOpcode(), Node->getValueType(0)); if (Action == TargetLowering::Expand) { Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp =================================================================== --- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -4627,6 +4627,22 @@ setValue(&I, DAG.getNode(ISD::FRAMEADDR, sdl, TLI->getPointerTy(), getValue(I.getArgOperand(0)))); return nullptr; + case Intrinsic::read_register: { + Value *Reg = I.getArgOperand(0); + SDValue RegName = DAG.getMDNode(cast(Reg)); + EVT VT = TM.getTargetLowering()->getValueType(I.getType()); + setValue(&I, DAG.getNode(ISD::READ_REGISTER, sdl, VT, RegName)); + return nullptr; + } + case Intrinsic::write_register: { + Value *Reg = I.getArgOperand(0); + Value *RegValue = I.getArgOperand(1); + SDValue Chain = getValue(RegValue).getOperand(0); + SDValue RegName = DAG.getMDNode(cast(Reg)); + DAG.setRoot(DAG.getNode(ISD::WRITE_REGISTER, sdl, MVT::Other, Chain, + RegName, getValue(RegValue))); + return nullptr; + } case Intrinsic::setjmp: return &"_setjmp"[!TLI->usesUnderscoreSetJmp()]; case Intrinsic::longjmp: Index: lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp =================================================================== --- lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp +++ lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp @@ -93,6 +93,8 @@ case ISD::GLOBAL_OFFSET_TABLE: return "GLOBAL_OFFSET_TABLE"; case ISD::RETURNADDR: return "RETURNADDR"; case ISD::FRAMEADDR: return "FRAMEADDR"; + case ISD::READ_REGISTER: return "READ_REGISTER"; + case ISD::WRITE_REGISTER: return "WRITE_REGISTER"; case ISD::FRAME_TO_ARGS_OFFSET: return "FRAME_TO_ARGS_OFFSET"; case ISD::EH_RETURN: return "EH_RETURN"; case ISD::EH_SJLJ_SETJMP: return "EH_SJLJ_SETJMP"; Index: lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp =================================================================== --- lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp +++ lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp @@ -1807,6 +1807,34 @@ return New.getNode(); } +SDNode +*SelectionDAGISel::Select_READ_REGISTER(SDNode *Op) { + SDLoc dl(Op); + MDNodeSDNode *MD = dyn_cast(Op->getOperand(0)); + const MDString *RegStr = dyn_cast(MD->getMD()->getOperand(0)); + unsigned Reg = getTargetLowering()->getRegisterByName( + RegStr->getString().data()); + SDValue New = CurDAG->getCopyFromReg( + CurDAG->getEntryNode(), dl, Reg, Op->getValueType(0)); + New->setNodeId(-1); + return New.getNode(); +} + +SDNode +*SelectionDAGISel::Select_WRITE_REGISTER(SDNode *Op) { + SDLoc dl(Op); + MDNodeSDNode *MD = dyn_cast(Op->getOperand(1)); + const MDString *RegStr = dyn_cast(MD->getMD()->getOperand(0)); + unsigned Reg = getTargetLowering()->getRegisterByName( + RegStr->getString().data()); + SDValue New = CurDAG->getCopyToReg( + CurDAG->getEntryNode(), dl, Reg, Op->getOperand(2)); + New->setNodeId(-1); + return New.getNode(); +} + + + SDNode *SelectionDAGISel::Select_UNDEF(SDNode *N) { return CurDAG->SelectNodeTo(N, TargetOpcode::IMPLICIT_DEF,N->getValueType(0)); } @@ -2399,6 +2427,8 @@ NodeToMatch->getOperand(0)); return nullptr; case ISD::INLINEASM: return Select_INLINEASM(NodeToMatch); + case ISD::READ_REGISTER: return Select_READ_REGISTER(NodeToMatch); + case ISD::WRITE_REGISTER: return Select_WRITE_REGISTER(NodeToMatch); case ISD::UNDEF: return Select_UNDEF(NodeToMatch); } Index: lib/Target/AArch64/AArch64ISelLowering.h =================================================================== --- lib/Target/AArch64/AArch64ISelLowering.h +++ lib/Target/AArch64/AArch64ISelLowering.h @@ -350,6 +350,8 @@ SDValue PerformDAGCombine(SDNode *N,DAGCombinerInfo &DCI) const override; + unsigned getRegisterByName(const char* RegName) const; + /// isFMAFasterThanFMulAndFAdd - Return true if an FMA operation is faster /// than a pair of fmul and fadd instructions. fmuladd intrinsics will be /// expanded to FMAs when this method returns true, otherwise fmuladd is Index: lib/Target/AArch64/AArch64ISelLowering.cpp =================================================================== --- lib/Target/AArch64/AArch64ISelLowering.cpp +++ lib/Target/AArch64/AArch64ISelLowering.cpp @@ -15,6 +15,7 @@ #include "AArch64.h" #include "AArch64ISelLowering.h" #include "AArch64MachineFunctionInfo.h" +#include "AArch64Subtarget.h" #include "AArch64TargetMachine.h" #include "AArch64TargetObjectFile.h" #include "Utils/AArch64BaseInfo.h" @@ -2406,6 +2407,17 @@ return FrameAddr; } +// FIXME? Maybe this could be a TableGen attribute on some registers and +// this table could be generated automatically from RegInfo. +unsigned AArch64TargetLowering::getRegisterByName(const char* RegName) const { + unsigned Reg = StringSwitch(RegName) + .Case("sp", AArch64::XSP) + .Default(0); + if (Reg) + return Reg; + report_fatal_error("Invalid register name global variable"); +} + SDValue AArch64TargetLowering::LowerGlobalAddressELFLarge(SDValue Op, SelectionDAG &DAG) const { Index: lib/Target/ARM/ARMISelLowering.h =================================================================== --- lib/Target/ARM/ARMISelLowering.h +++ lib/Target/ARM/ARMISelLowering.h @@ -461,6 +461,8 @@ SDValue LowerFSINCOS(SDValue Op, SelectionDAG &DAG) const; SDValue LowerDivRem(SDValue Op, SelectionDAG &DAG) const; + unsigned getRegisterByName(const char* RegName) const; + /// isFMAFasterThanFMulAndFAdd - Return true if an FMA operation is faster /// than a pair of fmul and fadd instructions. fmuladd intrinsics will be /// expanded to FMAs when this method returns true, otherwise fmuladd is Index: lib/Target/ARM/ARMISelLowering.cpp =================================================================== --- lib/Target/ARM/ARMISelLowering.cpp +++ lib/Target/ARM/ARMISelLowering.cpp @@ -3784,6 +3784,17 @@ return FrameAddr; } +// FIXME? Maybe this could be a TableGen attribute on some registers and +// this table could be generated automatically from RegInfo. +unsigned ARMTargetLowering::getRegisterByName(const char* RegName) const { + unsigned Reg = StringSwitch(RegName) + .Case("sp", ARM::SP) + .Default(0); + if (Reg) + return Reg; + report_fatal_error("Invalid register name global variable"); +} + /// ExpandBITCAST - If the target supports VFP, this function is called to /// expand a bit convert where either the source or destination type is i64 to /// use a VMOVDRR or VMOVRRD node. This should not be done when the non-i64 Index: lib/Target/ARM64/ARM64ISelLowering.h =================================================================== --- lib/Target/ARM64/ARM64ISelLowering.h +++ lib/Target/ARM64/ARM64ISelLowering.h @@ -388,6 +388,7 @@ ConstraintType getConstraintType(const std::string &Constraint) const override; + unsigned getRegisterByName(const char* RegName) const; /// Examine constraint string and operand type and determine a weight value. /// The operand object must already have been set up with the operand type. Index: lib/Target/ARM64/ARM64ISelLowering.cpp =================================================================== --- lib/Target/ARM64/ARM64ISelLowering.cpp +++ lib/Target/ARM64/ARM64ISelLowering.cpp @@ -3373,6 +3373,17 @@ return FrameAddr; } +// FIXME? Maybe this could be a TableGen attribute on some registers and +// this table could be generated automatically from RegInfo. +unsigned ARM64TargetLowering::getRegisterByName(const char* RegName) const { + unsigned Reg = StringSwitch(RegName) + .Case("sp", ARM64::SP) + .Default(0); + if (Reg) + return Reg; + report_fatal_error("Invalid register name global variable"); +} + SDValue ARM64TargetLowering::LowerRETURNADDR(SDValue Op, SelectionDAG &DAG) const { MachineFunction &MF = DAG.getMachineFunction(); Index: lib/Target/X86/X86ISelLowering.h =================================================================== --- lib/Target/X86/X86ISelLowering.h +++ lib/Target/X86/X86ISelLowering.h @@ -786,6 +786,8 @@ return nullptr; // nothing to do, move along. } + unsigned getRegisterByName(const char* RegName) const; + /// createFastISel - This method returns a target specific FastISel object, /// or null if the target does not support "fast" ISel. FastISel *createFastISel(FunctionLoweringInfo &funcInfo, Index: lib/Target/X86/X86ISelLowering.cpp =================================================================== --- lib/Target/X86/X86ISelLowering.cpp +++ lib/Target/X86/X86ISelLowering.cpp @@ -22,6 +22,7 @@ #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/StringExtras.h" +#include "llvm/ADT/StringSwitch.h" #include "llvm/ADT/VariadicFunction.h" #include "llvm/CodeGen/IntrinsicLowering.h" #include "llvm/CodeGen/MachineFrameInfo.h" @@ -12726,6 +12727,18 @@ return FrameAddr; } +// FIXME? Maybe this could be a TableGen attribute on some registers and +// this table could be generated automatically from RegInfo. +unsigned X86TargetLowering::getRegisterByName(const char* RegName) const { + unsigned Reg = StringSwitch(RegName) + .Case("esp", X86::ESP) + .Case("rsp", X86::RSP) + .Default(0); + if (Reg) + return Reg; + report_fatal_error("Invalid register name global variable"); +} + SDValue X86TargetLowering::LowerFRAME_TO_ARGS_OFFSET(SDValue Op, SelectionDAG &DAG) const { const X86RegisterInfo *RegInfo = Index: test/CodeGen/AArch64/named-reg-alloc.ll =================================================================== --- /dev/null +++ test/CodeGen/AArch64/named-reg-alloc.ll @@ -0,0 +1,13 @@ +; RUN: not llc < %s -mtriple=aarch64-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; FIXME: Include an allocatable-specific error message +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"x5\00"} Index: test/CodeGen/AArch64/named-reg-notareg.ll =================================================================== --- /dev/null +++ test/CodeGen/AArch64/named-reg-notareg.ll @@ -0,0 +1,12 @@ +; RUN: not llc < %s -mtriple=aarch64-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"notareg\00"} Index: test/CodeGen/AArch64/stackpointer.ll =================================================================== --- /dev/null +++ test/CodeGen/AArch64/stackpointer.ll @@ -0,0 +1,24 @@ +; RUN: llc < %s -mtriple=aarch64-linux-gnueabi | FileCheck %s + +define i64 @get_stack() nounwind { +entry: +; CHECK-LABEL: get_stack: +; CHECK: mov x0, sp + %sp = call i64 @llvm.read_register.i64(metadata !0) + ret i64 %sp +} + +define void @set_stack(i64 %val) nounwind { +entry: +; CHECK-LABEL: set_stack: +; CHECK: mov sp, x0 + call void @llvm.write_register.i64(metadata !0, i64 %val) + ret void +} + +declare i64 @llvm.read_register.i64(metadata) nounwind +declare void @llvm.write_register.i64(metadata, i64) nounwind + +; register unsigned long current_stack_pointer asm("sp"); +; CHECK-NOT: .asciz "sp" +!0 = metadata !{metadata !"sp\00"} Index: test/CodeGen/ARM/named-reg-alloc.ll =================================================================== --- /dev/null +++ test/CodeGen/ARM/named-reg-alloc.ll @@ -0,0 +1,14 @@ +; RUN: not llc < %s -mtriple=arm-apple-darwin 2>&1 | FileCheck %s +; RUN: not llc < %s -mtriple=arm-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; FIXME: Include an allocatable-specific error message +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"r5\00"} Index: test/CodeGen/ARM/named-reg-notareg.ll =================================================================== --- /dev/null +++ test/CodeGen/ARM/named-reg-notareg.ll @@ -0,0 +1,13 @@ +; RUN: not llc < %s -mtriple=arm-apple-darwin 2>&1 | FileCheck %s +; RUN: not llc < %s -mtriple=arm-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"notareg\00"} Index: test/CodeGen/ARM/stackpointer.ll =================================================================== --- /dev/null +++ test/CodeGen/ARM/stackpointer.ll @@ -0,0 +1,25 @@ +; RUN: llc < %s -mtriple=arm-apple-darwin | FileCheck %s +; RUN: llc < %s -mtriple=arm-linux-gnueabi | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; CHECK-LABEL: get_stack: +; CHECK: mov r0, sp + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +define void @set_stack(i32 %val) nounwind { +entry: +; CHECK-LABEL: set_stack: +; CHECK: mov sp, r0 + call void @llvm.write_register.i32(metadata !0, i32 %val) + ret void +} + +declare i32 @llvm.read_register.i32(metadata) nounwind +declare void @llvm.write_register.i32(metadata, i32) nounwind + +; register unsigned long current_stack_pointer asm("sp"); +; CHECK-NOT: .asciz "sp" +!0 = metadata !{metadata !"sp\00"} Index: test/CodeGen/ARM64/named-reg-alloc.ll =================================================================== --- /dev/null +++ test/CodeGen/ARM64/named-reg-alloc.ll @@ -0,0 +1,14 @@ +; RUN: not llc < %s -mtriple=arm64-apple-darwin 2>&1 | FileCheck %s +; RUN: not llc < %s -mtriple=arm64-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; FIXME: Include an allocatable-specific error message +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"x5\00"} Index: test/CodeGen/ARM64/named-reg-notareg.ll =================================================================== --- /dev/null +++ test/CodeGen/ARM64/named-reg-notareg.ll @@ -0,0 +1,13 @@ +; RUN: not llc < %s -mtriple=arm64-apple-darwin 2>&1 | FileCheck %s +; RUN: not llc < %s -mtriple=arm64-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"notareg\00"} Index: test/CodeGen/ARM64/stackpointer.ll =================================================================== --- /dev/null +++ test/CodeGen/ARM64/stackpointer.ll @@ -0,0 +1,24 @@ +; RUN: llc < %s -mtriple=arm64-linux-gnu | FileCheck %s + +define i64 @get_stack() nounwind { +entry: +; CHECK-LABEL: get_stack: +; CHECK: mov x0, sp + %sp = call i64 @llvm.read_register.i64(metadata !0) + ret i64 %sp +} + +define void @set_stack(i64 %val) nounwind { +entry: +; CHECK-LABEL: set_stack: +; CHECK: mov sp, x0 + call void @llvm.write_register.i64(metadata !0, i64 %val) + ret void +} + +declare i64 @llvm.read_register.i64(metadata) nounwind +declare void @llvm.write_register.i64(metadata, i64) nounwind + +; register unsigned long current_stack_pointer asm("sp"); +; CHECK-NOT: .asciz "sp" +!0 = metadata !{metadata !"sp\00"} Index: test/CodeGen/X86/named-reg-alloc.ll =================================================================== --- /dev/null +++ test/CodeGen/X86/named-reg-alloc.ll @@ -0,0 +1,14 @@ +; RUN: not llc < %s -mtriple=x86_64-apple-darwin 2>&1 | FileCheck %s +; RUN: not llc < %s -mtriple=x86_64-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; FIXME: Include an allocatable-specific error message +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"eax\00"} Index: test/CodeGen/X86/named-reg-notareg.ll =================================================================== --- /dev/null +++ test/CodeGen/X86/named-reg-notareg.ll @@ -0,0 +1,13 @@ +; RUN: not llc < %s -mtriple=x86_64-apple-darwin 2>&1 | FileCheck %s +; RUN: not llc < %s -mtriple=x86_64-linux-gnueabi 2>&1 | FileCheck %s + +define i32 @get_stack() nounwind { +entry: +; CHECK: Invalid register name global variable + %sp = call i32 @llvm.read_register.i32(metadata !0) + ret i32 %sp +} + +declare i32 @llvm.read_register.i32(metadata) nounwind + +!0 = metadata !{metadata !"notareg\00"} Index: test/CodeGen/X86/stackpointer.ll =================================================================== --- /dev/null +++ test/CodeGen/X86/stackpointer.ll @@ -0,0 +1,25 @@ +; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s +; RUN: llc < %s -mtriple=x86_64-linux-gnueabi | FileCheck %s + +define i64 @get_stack() nounwind { +entry: +; CHECK-LABEL: get_stack: +; CHECK: movq %rsp, %rax + %sp = call i64 @llvm.read_register.i64(metadata !0) + ret i64 %sp +} + +define void @set_stack(i64 %val) nounwind { +entry: +; CHECK-LABEL: set_stack: +; CHECK: movq %rdi, %rsp + call void @llvm.write_register.i64(metadata !0, i64 %val) + ret void +} + +declare i64 @llvm.read_register.i64(metadata) nounwind +declare void @llvm.write_register.i64(metadata, i64) nounwind + +; register unsigned long current_stack_pointer asm("rsp"); +; CHECK-NOT: .asciz "rsp" +!0 = metadata !{metadata !"rsp\00"}