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

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// WebAssemblyMCInstLower.cpp - Convert WebAssembly MachineInstr to an MCInst //
//
// 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 contains code to lower WebAssembly MachineInstrs to their
/// corresponding MCInst records.
///
//===----------------------------------------------------------------------===//
#include "WebAssemblyMCInstLower.h"
#include "WebAssemblyAsmPrinter.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblyRuntimeLibcallSignatures.h"
#include "WebAssemblyUtilities.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/IR/Constants.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/MC/MCSymbolWasm.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
MCSymbol *
WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
const GlobalValue *Global = MO.getGlobal();
MCSymbol *Sym = Printer.getSymbol(Global);
if (isa<MCSymbolELF>(Sym))
return Sym;
MCSymbolWasm *WasmSym = cast<MCSymbolWasm>(Sym);
if (const auto *FuncTy = dyn_cast<FunctionType>(Global->getValueType())) {
const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
const TargetMachine &TM = MF.getTarget();
const Function &CurrentFunc = MF.getFunction();
SmallVector<wasm::ValType, 4> Returns;
SmallVector<wasm::ValType, 4> Params;
wasm::ValType iPTR =
MF.getSubtarget<WebAssemblySubtarget>().hasAddr64() ?
wasm::ValType::I64 :
wasm::ValType::I32;
SmallVector<MVT, 4> ResultMVTs;
ComputeLegalValueVTs(CurrentFunc, TM, FuncTy->getReturnType(), ResultMVTs);
// WebAssembly can't currently handle returning tuples.
if (ResultMVTs.size() <= 1)
for (MVT ResultMVT : ResultMVTs)
Returns.push_back(WebAssembly::toValType(ResultMVT));
else
Params.push_back(iPTR);
for (Type *Ty : FuncTy->params()) {
SmallVector<MVT, 4> ParamMVTs;
ComputeLegalValueVTs(CurrentFunc, TM, Ty, ParamMVTs);
for (MVT ParamMVT : ParamMVTs)
Params.push_back(WebAssembly::toValType(ParamMVT));
}
if (FuncTy->isVarArg())
Params.push_back(iPTR);
WasmSym->setReturns(std::move(Returns));
WasmSym->setParams(std::move(Params));
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
}
return WasmSym;
}
MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
const MachineOperand &MO) const {
const char *Name = MO.getSymbolName();
MCSymbol *Sym = Printer.GetExternalSymbolSymbol(Name);
if (isa<MCSymbolELF>(Sym))
return Sym;
MCSymbolWasm *WasmSym = cast<MCSymbolWasm>(Sym);
const WebAssemblySubtarget &Subtarget = Printer.getSubtarget();
// __stack_pointer is a global variable; all other external symbols used by
// CodeGen are functions. It's OK to hardcode knowledge of specific symbols
// here; this method is precisely there for fetching the signatures of known
// Clang-provided symbols.
if (strcmp(Name, "__stack_pointer") == 0) {
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
WasmSym->setGlobalType(wasm::WasmGlobalType{
uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64
: wasm::WASM_TYPE_I32),
true});
return WasmSym;
}
SmallVector<wasm::ValType, 4> Returns;
SmallVector<wasm::ValType, 4> Params;
GetSignature(Subtarget, Name, Returns, Params);
WasmSym->setReturns(std::move(Returns));
WasmSym->setParams(std::move(Params));
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
return WasmSym;
}
MCOperand WebAssemblyMCInstLower::LowerSymbolOperand(MCSymbol *Sym,
int64_t Offset,
bool IsFunc) const {
MCSymbolRefExpr::VariantKind VK =
IsFunc ? MCSymbolRefExpr::VK_WebAssembly_FUNCTION
: MCSymbolRefExpr::VK_None;
const MCExpr *Expr = MCSymbolRefExpr::create(Sym, VK, Ctx);
if (Offset != 0) {
if (IsFunc)
report_fatal_error("Function addresses with offsets not supported");
Expr =
MCBinaryExpr::createAdd(Expr, MCConstantExpr::create(Offset, Ctx), Ctx);
}
return MCOperand::createExpr(Expr);
}
// Return the WebAssembly type associated with the given register class.
static wasm::ValType getType(const TargetRegisterClass *RC) {
if (RC == &WebAssembly::I32RegClass)
return wasm::ValType::I32;
if (RC == &WebAssembly::I64RegClass)
return wasm::ValType::I64;
if (RC == &WebAssembly::F32RegClass)
return wasm::ValType::F32;
if (RC == &WebAssembly::F64RegClass)
return wasm::ValType::F64;
llvm_unreachable("Unexpected register class");
}
void WebAssemblyMCInstLower::Lower(const MachineInstr *MI,
MCInst &OutMI) const {
OutMI.setOpcode(MI->getOpcode());
const MCInstrDesc &Desc = MI->getDesc();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
MCOperand MCOp;
switch (MO.getType()) {
default:
MI->print(errs());
llvm_unreachable("unknown operand type");
case MachineOperand::MO_MachineBasicBlock:
MI->print(errs());
llvm_unreachable("MachineBasicBlock operand should have been rewritten");
case MachineOperand::MO_Register: {
// Ignore all implicit register operands.
if (MO.isImplicit())
continue;
const WebAssemblyFunctionInfo &MFI =
*MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
unsigned WAReg = MFI.getWAReg(MO.getReg());
MCOp = MCOperand::createReg(WAReg);
break;
}
case MachineOperand::MO_Immediate:
if (i < Desc.NumOperands) {
const MCOperandInfo &Info = Desc.OpInfo[i];
if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
MCSymbol *Sym = Printer.createTempSymbol("typeindex");
if (!isa<MCSymbolELF>(Sym)) {
SmallVector<wasm::ValType, 4> Returns;
SmallVector<wasm::ValType, 4> Params;
const MachineRegisterInfo &MRI =
MI->getParent()->getParent()->getRegInfo();
for (const MachineOperand &MO : MI->defs())
Returns.push_back(getType(MRI.getRegClass(MO.getReg())));
for (const MachineOperand &MO : MI->explicit_uses())
if (MO.isReg())
Params.push_back(getType(MRI.getRegClass(MO.getReg())));
// call_indirect instructions have a callee operand at the end which
// doesn't count as a param.
if (WebAssembly::isCallIndirect(*MI))
Params.pop_back();
MCSymbolWasm *WasmSym = cast<MCSymbolWasm>(Sym);
WasmSym->setReturns(std::move(Returns));
WasmSym->setParams(std::move(Params));
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
const MCExpr *Expr =
MCSymbolRefExpr::create(WasmSym,
MCSymbolRefExpr::VK_WebAssembly_TYPEINDEX,
Ctx);
MCOp = MCOperand::createExpr(Expr);
break;
}
}
}
MCOp = MCOperand::createImm(MO.getImm());
break;
case MachineOperand::MO_FPImmediate: {
// TODO: MC converts all floating point immediate operands to double.
// This is fine for numeric values, but may cause NaNs to change bits.
const ConstantFP *Imm = MO.getFPImm();
if (Imm->getType()->isFloatTy())
MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToFloat());
else if (Imm->getType()->isDoubleTy())
MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToDouble());
else
llvm_unreachable("unknown floating point immediate type");
break;
}
case MachineOperand::MO_GlobalAddress:
assert(MO.getTargetFlags() == 0 &&
"WebAssembly does not use target flags on GlobalAddresses");
MCOp = LowerSymbolOperand(GetGlobalAddressSymbol(MO), MO.getOffset(),
MO.getGlobal()->getValueType()->isFunctionTy());
break;
case MachineOperand::MO_ExternalSymbol:
// The target flag indicates whether this is a symbol for a
// variable or a function.
assert((MO.getTargetFlags() & -2) == 0 &&
"WebAssembly uses only one target flag bit on ExternalSymbols");
MCOp = LowerSymbolOperand(GetExternalSymbolSymbol(MO), /*Offset=*/0,
MO.getTargetFlags() & 1);
break;
}
OutMI.addOperand(MCOp);
}
}
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