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llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp

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//=- WebAssemblyISelLowering.cpp - WebAssembly DAG Lowering Implementation -==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file implements the WebAssemblyTargetLowering class.
///
//===----------------------------------------------------------------------===//
#include "WebAssemblyISelLowering.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "WebAssemblyTargetMachine.h"
#include "WebAssemblyTargetObjectFile.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-lower"
namespace {
// Diagnostic information for unimplemented or unsupported feature reporting.
// TODO: This code is copied from BPF and AMDGPU; consider factoring it out
// and sharing code.
class DiagnosticInfoUnsupported final : public DiagnosticInfo {
private:
// Debug location where this diagnostic is triggered.
DebugLoc DLoc;
const Twine &Description;
const Function &Fn;
SDValue Value;
static int KindID;
static int getKindID() {
if (KindID == 0)
KindID = llvm::getNextAvailablePluginDiagnosticKind();
return KindID;
}
public:
DiagnosticInfoUnsupported(SDLoc DLoc, const Function &Fn, const Twine &Desc,
SDValue Value)
: DiagnosticInfo(getKindID(), DS_Error), DLoc(DLoc.getDebugLoc()),
Description(Desc), Fn(Fn), Value(Value) {}
void print(DiagnosticPrinter &DP) const override {
std::string Str;
raw_string_ostream OS(Str);
if (DLoc) {
auto DIL = DLoc.get();
StringRef Filename = DIL->getFilename();
unsigned Line = DIL->getLine();
unsigned Column = DIL->getColumn();
OS << Filename << ':' << Line << ':' << Column << ' ';
}
OS << "in function " << Fn.getName() << ' ' << *Fn.getFunctionType() << '\n'
<< Description;
if (Value)
Value->print(OS);
OS << '\n';
OS.flush();
DP << Str;
}
static bool classof(const DiagnosticInfo *DI) {
return DI->getKind() == getKindID();
}
};
int DiagnosticInfoUnsupported::KindID = 0;
} // end anonymous namespace
WebAssemblyTargetLowering::WebAssemblyTargetLowering(
const TargetMachine &TM, const WebAssemblySubtarget &STI)
: TargetLowering(TM), Subtarget(&STI) {
auto MVTPtr = Subtarget->hasAddr64() ? MVT::i64 : MVT::i32;
// Booleans always contain 0 or 1.
setBooleanContents(ZeroOrOneBooleanContent);
// WebAssembly does not produce floating-point exceptions on normal floating
// point operations.
setHasFloatingPointExceptions(false);
// We don't know the microarchitecture here, so just reduce register pressure.
setSchedulingPreference(Sched::RegPressure);
// Tell ISel that we have a stack pointer.
setStackPointerRegisterToSaveRestore(
Subtarget->hasAddr64() ? WebAssembly::SP64 : WebAssembly::SP32);
// Set up the register classes.
addRegisterClass(MVT::i32, &WebAssembly::I32RegClass);
addRegisterClass(MVT::i64, &WebAssembly::I64RegClass);
addRegisterClass(MVT::f32, &WebAssembly::F32RegClass);
addRegisterClass(MVT::f64, &WebAssembly::F64RegClass);
// Compute derived properties from the register classes.
computeRegisterProperties(Subtarget->getRegisterInfo());
setOperationAction(ISD::GlobalAddress, MVTPtr, Custom);
setOperationAction(ISD::ExternalSymbol, MVTPtr, Custom);
setOperationAction(ISD::JumpTable, MVTPtr, Custom);
for (auto T : {MVT::f32, MVT::f64}) {
// Don't expand the floating-point types to constant pools.
setOperationAction(ISD::ConstantFP, T, Legal);
// Expand floating-point comparisons.
for (auto CC : {ISD::SETO, ISD::SETUO, ISD::SETUEQ, ISD::SETONE,
ISD::SETULT, ISD::SETULE, ISD::SETUGT, ISD::SETUGE})
setCondCodeAction(CC, T, Expand);
// Expand floating-point library function operators.
for (auto Op : {ISD::FSIN, ISD::FCOS, ISD::FSINCOS, ISD::FPOWI, ISD::FPOW})
setOperationAction(Op, T, Expand);
// Note supported floating-point library function operators that otherwise
// default to expand.
for (auto Op :
{ISD::FCEIL, ISD::FFLOOR, ISD::FTRUNC, ISD::FNEARBYINT, ISD::FRINT})
setOperationAction(Op, T, Legal);
// Support minnan and maxnan, which otherwise default to expand.
setOperationAction(ISD::FMINNAN, T, Legal);
setOperationAction(ISD::FMAXNAN, T, Legal);
}
for (auto T : {MVT::i32, MVT::i64}) {
// Expand unavailable integer operations.
for (auto Op :
{ISD::BSWAP, ISD::ROTL, ISD::ROTR, ISD::SMUL_LOHI, ISD::UMUL_LOHI,
ISD::MULHS, ISD::MULHU, ISD::SDIVREM, ISD::UDIVREM, ISD::SHL_PARTS,
ISD::SRA_PARTS, ISD::SRL_PARTS, ISD::ADDC, ISD::ADDE, ISD::SUBC,
ISD::SUBE}) {
setOperationAction(Op, T, Expand);
}
}
// As a special case, these operators use the type to mean the type to
// sign-extend from.
for (auto T : {MVT::i1, MVT::i8, MVT::i16})
setOperationAction(ISD::SIGN_EXTEND_INREG, T, Expand);
// Dynamic stack allocation: use the default expansion.
setOperationAction(ISD::STACKSAVE, MVT::Other, Expand);
setOperationAction(ISD::STACKRESTORE, MVT::Other, Expand);
setOperationAction(ISD::DYNAMIC_STACKALLOC, MVTPtr, Expand);
// Expand these forms; we pattern-match the forms that we can handle in isel.
for (auto T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
for (auto Op : {ISD::BR_CC, ISD::SELECT_CC})
setOperationAction(Op, T, Expand);
// We have custom switch handling.
setOperationAction(ISD::BR_JT, MVT::Other, Custom);
// WebAssembly doesn't have:
// - Floating-point extending loads.
// - Floating-point truncating stores.
// - i1 extending loads.
setLoadExtAction(ISD::EXTLOAD, MVT::f32, MVT::f64, Expand);
setTruncStoreAction(MVT::f64, MVT::f32, Expand);
for (auto T : MVT::integer_valuetypes())
for (auto Ext : {ISD::EXTLOAD, ISD::ZEXTLOAD, ISD::SEXTLOAD})
setLoadExtAction(Ext, T, MVT::i1, Promote);
// Trap lowers to wasm unreachable
setOperationAction(ISD::TRAP, MVT::Other, Legal);
}
FastISel *WebAssemblyTargetLowering::createFastISel(
FunctionLoweringInfo &FuncInfo, const TargetLibraryInfo *LibInfo) const {
return WebAssembly::createFastISel(FuncInfo, LibInfo);
}
bool WebAssemblyTargetLowering::isOffsetFoldingLegal(
const GlobalAddressSDNode * /*GA*/) const {
// The WebAssembly target doesn't support folding offsets into global
// addresses.
return false;
}
MVT WebAssemblyTargetLowering::getScalarShiftAmountTy(const DataLayout & /*DL*/,
EVT VT) const {
return VT.getSimpleVT();
}
const char *
WebAssemblyTargetLowering::getTargetNodeName(unsigned Opcode) const {
switch (static_cast<WebAssemblyISD::NodeType>(Opcode)) {
case WebAssemblyISD::FIRST_NUMBER:
break;
#define HANDLE_NODETYPE(NODE) \
case WebAssemblyISD::NODE: \
return "WebAssemblyISD::" #NODE;
#include "WebAssemblyISD.def"
#undef HANDLE_NODETYPE
}
return nullptr;
}
std::pair<unsigned, const TargetRegisterClass *>
WebAssemblyTargetLowering::getRegForInlineAsmConstraint(
const TargetRegisterInfo *TRI, StringRef Constraint, MVT VT) const {
// First, see if this is a constraint that directly corresponds to a
// WebAssembly register class.
if (Constraint.size() == 1) {
switch (Constraint[0]) {
case 'r':
if (VT == MVT::i32)
return std::make_pair(0U, &WebAssembly::I32RegClass);
if (VT == MVT::i64)
return std::make_pair(0U, &WebAssembly::I64RegClass);
break;
default:
break;
}
}
return TargetLowering::getRegForInlineAsmConstraint(TRI, Constraint, VT);
}
bool WebAssemblyTargetLowering::isCheapToSpeculateCttz() const {
// Assume ctz is a relatively cheap operation.
return true;
}
bool WebAssemblyTargetLowering::isCheapToSpeculateCtlz() const {
// Assume clz is a relatively cheap operation.
return true;
}
//===----------------------------------------------------------------------===//
// WebAssembly Lowering private implementation.
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
// Lowering Code
//===----------------------------------------------------------------------===//
static void fail(SDLoc DL, SelectionDAG &DAG, const char *msg) {
MachineFunction &MF = DAG.getMachineFunction();
DAG.getContext()->diagnose(
DiagnosticInfoUnsupported(DL, *MF.getFunction(), msg, SDValue()));
}
// Test whether the given calling convention is supported.
static bool CallingConvSupported(CallingConv::ID CallConv) {
// We currently support the language-independent target-independent
// conventions. We don't yet have a way to annotate calls with properties like
// "cold", and we don't have any call-clobbered registers, so these are mostly
// all handled the same.
return CallConv == CallingConv::C || CallConv == CallingConv::Fast ||
CallConv == CallingConv::Cold ||
CallConv == CallingConv::PreserveMost ||
CallConv == CallingConv::PreserveAll ||
CallConv == CallingConv::CXX_FAST_TLS;
}
SDValue
WebAssemblyTargetLowering::LowerCall(CallLoweringInfo &CLI,
SmallVectorImpl<SDValue> &InVals) const {
SelectionDAG &DAG = CLI.DAG;
SDLoc DL = CLI.DL;
SDValue Chain = CLI.Chain;
SDValue Callee = CLI.Callee;
MachineFunction &MF = DAG.getMachineFunction();
CallingConv::ID CallConv = CLI.CallConv;
if (!CallingConvSupported(CallConv))
fail(DL, DAG,
"WebAssembly doesn't support language-specific or target-specific "
"calling conventions yet");
if (CLI.IsPatchPoint)
fail(DL, DAG, "WebAssembly doesn't support patch point yet");
// WebAssembly doesn't currently support explicit tail calls. If they are
// required, fail. Otherwise, just disable them.
if ((CallConv == CallingConv::Fast && CLI.IsTailCall &&
MF.getTarget().Options.GuaranteedTailCallOpt) ||
(CLI.CS && CLI.CS->isMustTailCall()))
fail(DL, DAG, "WebAssembly doesn't support tail call yet");
CLI.IsTailCall = false;
SmallVectorImpl<SDValue> &OutVals = CLI.OutVals;
SmallVectorImpl<ISD::InputArg> &Ins = CLI.Ins;
if (Ins.size() > 1)
fail(DL, DAG, "WebAssembly doesn't support more than 1 returned value yet");
SmallVectorImpl<ISD::OutputArg> &Outs = CLI.Outs;
for (const ISD::OutputArg &Out : Outs) {
assert(!Out.Flags.isByVal() && "byval is not valid for return values");
assert(!Out.Flags.isNest() && "nest is not valid for return values");
if (Out.Flags.isInAlloca())
fail(DL, DAG, "WebAssembly hasn't implemented inalloca results");
if (Out.Flags.isInConsecutiveRegs())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs results");
if (Out.Flags.isInConsecutiveRegsLast())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs last results");
}
bool IsVarArg = CLI.IsVarArg;
if (IsVarArg)
fail(DL, DAG, "WebAssembly doesn't support varargs yet");
// Analyze operands of the call, assigning locations to each operand.
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(CallConv, IsVarArg, MF, ArgLocs, *DAG.getContext());
unsigned NumBytes = CCInfo.getNextStackOffset();
auto PtrVT = getPointerTy(MF.getDataLayout());
auto Zero = DAG.getConstant(0, DL, PtrVT, true);
auto NB = DAG.getConstant(NumBytes, DL, PtrVT, true);
Chain = DAG.getCALLSEQ_START(Chain, NB, DL);
SmallVector<SDValue, 16> Ops;
Ops.push_back(Chain);
Ops.push_back(Callee);
Ops.append(OutVals.begin(), OutVals.end());
SmallVector<EVT, 8> Tys;
for (const auto &In : Ins) {
if (In.Flags.isByVal())
fail(DL, DAG, "WebAssembly hasn't implemented byval arguments");
if (In.Flags.isInAlloca())
fail(DL, DAG, "WebAssembly hasn't implemented inalloca arguments");
if (In.Flags.isNest())
fail(DL, DAG, "WebAssembly hasn't implemented nest arguments");
if (In.Flags.isInConsecutiveRegs())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs arguments");
if (In.Flags.isInConsecutiveRegsLast())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs last arguments");
// Ignore In.getOrigAlign() because all our arguments are passed in
// registers.
Tys.push_back(In.VT);
}
Tys.push_back(MVT::Other);
SDVTList TyList = DAG.getVTList(Tys);
SDValue Res =
DAG.getNode(Ins.empty() ? WebAssemblyISD::CALL0 : WebAssemblyISD::CALL1,
DL, TyList, Ops);
if (Ins.empty()) {
Chain = Res;
} else {
InVals.push_back(Res);
Chain = Res.getValue(1);
}
Chain = DAG.getCALLSEQ_END(Chain, NB, Zero, SDValue(), DL);
return Chain;
}
bool WebAssemblyTargetLowering::CanLowerReturn(
CallingConv::ID /*CallConv*/, MachineFunction & /*MF*/, bool /*IsVarArg*/,
const SmallVectorImpl<ISD::OutputArg> &Outs,
LLVMContext & /*Context*/) const {
// WebAssembly can't currently handle returning tuples.
return Outs.size() <= 1;
}
SDValue WebAssemblyTargetLowering::LowerReturn(
SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
const SmallVectorImpl<ISD::OutputArg> &Outs,
const SmallVectorImpl<SDValue> &OutVals, SDLoc DL,
SelectionDAG &DAG) const {
assert(Outs.size() <= 1 && "WebAssembly can only return up to one value");
if (!CallingConvSupported(CallConv))
fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
if (IsVarArg)
fail(DL, DAG, "WebAssembly doesn't support varargs yet");
SmallVector<SDValue, 4> RetOps(1, Chain);
RetOps.append(OutVals.begin(), OutVals.end());
Chain = DAG.getNode(WebAssemblyISD::RETURN, DL, MVT::Other, RetOps);
// Record the number and types of the return values.
for (const ISD::OutputArg &Out : Outs) {
assert(!Out.Flags.isByVal() && "byval is not valid for return values");
assert(!Out.Flags.isNest() && "nest is not valid for return values");
if (Out.Flags.isInAlloca())
fail(DL, DAG, "WebAssembly hasn't implemented inalloca results");
if (Out.Flags.isInConsecutiveRegs())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs results");
if (Out.Flags.isInConsecutiveRegsLast())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs last results");
if (!Out.IsFixed)
fail(DL, DAG, "WebAssembly doesn't support non-fixed results yet");
}
return Chain;
}
SDValue WebAssemblyTargetLowering::LowerFormalArguments(
SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
const SmallVectorImpl<ISD::InputArg> &Ins, SDLoc DL, SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals) const {
MachineFunction &MF = DAG.getMachineFunction();
if (!CallingConvSupported(CallConv))
fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
if (IsVarArg)
fail(DL, DAG, "WebAssembly doesn't support varargs yet");
// Set up the incoming ARGUMENTS value, which serves to represent the liveness
// of the incoming values before they're represented by virtual registers.
MF.getRegInfo().addLiveIn(WebAssembly::ARGUMENTS);
for (const ISD::InputArg &In : Ins) {
if (In.Flags.isByVal())
fail(DL, DAG, "WebAssembly hasn't implemented byval arguments");
if (In.Flags.isInAlloca())
fail(DL, DAG, "WebAssembly hasn't implemented inalloca arguments");
if (In.Flags.isNest())
fail(DL, DAG, "WebAssembly hasn't implemented nest arguments");
if (In.Flags.isInConsecutiveRegs())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs arguments");
if (In.Flags.isInConsecutiveRegsLast())
fail(DL, DAG, "WebAssembly hasn't implemented cons regs last arguments");
// Ignore In.getOrigAlign() because all our arguments are passed in
// registers.
InVals.push_back(
In.Used
? DAG.getNode(WebAssemblyISD::ARGUMENT, DL, In.VT,
DAG.getTargetConstant(InVals.size(), DL, MVT::i32))
: DAG.getUNDEF(In.VT));
// Record the number and types of arguments.
MF.getInfo<WebAssemblyFunctionInfo>()->addParam(In.VT);
}
return Chain;
}
//===----------------------------------------------------------------------===//
// Custom lowering hooks.
//===----------------------------------------------------------------------===//
SDValue WebAssemblyTargetLowering::LowerOperation(SDValue Op,
SelectionDAG &DAG) const {
switch (Op.getOpcode()) {
default:
llvm_unreachable("unimplemented operation lowering");
return SDValue();
case ISD::GlobalAddress:
return LowerGlobalAddress(Op, DAG);
case ISD::ExternalSymbol:
return LowerExternalSymbol(Op, DAG);
case ISD::JumpTable:
return LowerJumpTable(Op, DAG);
case ISD::BR_JT:
return LowerBR_JT(Op, DAG);
}
}
SDValue WebAssemblyTargetLowering::LowerGlobalAddress(SDValue Op,
SelectionDAG &DAG) const {
SDLoc DL(Op);
const auto *GA = cast<GlobalAddressSDNode>(Op);
EVT VT = Op.getValueType();
assert(GA->getOffset() == 0 &&
"offsets on global addresses are forbidden by isOffsetFoldingLegal");
assert(GA->getTargetFlags() == 0 && "WebAssembly doesn't set target flags");
if (GA->getAddressSpace() != 0)
fail(DL, DAG, "WebAssembly only expects the 0 address space");
return DAG.getNode(WebAssemblyISD::Wrapper, DL, VT,
DAG.getTargetGlobalAddress(GA->getGlobal(), DL, VT));
}
SDValue
WebAssemblyTargetLowering::LowerExternalSymbol(SDValue Op,
SelectionDAG &DAG) const {
SDLoc DL(Op);
const auto *ES = cast<ExternalSymbolSDNode>(Op);
EVT VT = Op.getValueType();
assert(ES->getTargetFlags() == 0 && "WebAssembly doesn't set target flags");
return DAG.getNode(WebAssemblyISD::Wrapper, DL, VT,
DAG.getTargetExternalSymbol(ES->getSymbol(), VT));
}
SDValue WebAssemblyTargetLowering::LowerJumpTable(SDValue Op,
SelectionDAG &DAG) const {
// There's no need for a Wrapper node because we always incorporate a jump
// table operand into a TABLESWITCH instruction, rather than ever
// materializing it in a register.
const JumpTableSDNode *JT = cast<JumpTableSDNode>(Op);
return DAG.getTargetJumpTable(JT->getIndex(), Op.getValueType(),
JT->getTargetFlags());
}
SDValue WebAssemblyTargetLowering::LowerBR_JT(SDValue Op,
SelectionDAG &DAG) const {
SDLoc DL(Op);
SDValue Chain = Op.getOperand(0);
const auto *JT = cast<JumpTableSDNode>(Op.getOperand(1));
SDValue Index = Op.getOperand(2);
assert(JT->getTargetFlags() == 0 && "WebAssembly doesn't set target flags");
SmallVector<SDValue, 8> Ops;
Ops.push_back(Chain);
Ops.push_back(Index);
MachineJumpTableInfo *MJTI = DAG.getMachineFunction().getJumpTableInfo();
const auto &MBBs = MJTI->getJumpTables()[JT->getIndex()].MBBs;
// TODO: For now, we just pick something arbitrary for a default case for now.
// We really want to sniff out the guard and put in the real default case (and
// delete the guard).
Ops.push_back(DAG.getBasicBlock(MBBs[0]));
// Add an operand for each case.
for (auto MBB : MBBs)
Ops.push_back(DAG.getBasicBlock(MBB));
return DAG.getNode(WebAssemblyISD::TABLESWITCH, DL, MVT::Other, Ops);
}
//===----------------------------------------------------------------------===//
// WebAssembly Optimization Hooks
//===----------------------------------------------------------------------===//
MCSection *WebAssemblyTargetObjectFile::SelectSectionForGlobal(
const GlobalValue *GV, SectionKind /*Kind*/, Mangler & /*Mang*/,
const TargetMachine & /*TM*/) const {
// TODO: Be more sophisticated than this.
return isa<Function>(GV) ? getTextSection() : getDataSection();
}
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