1 files changed, 341 insertions, 0 deletions
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
new file mode 100644
index 000000000000..59c10243c545
--- /dev/null
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
@@ -0,0 +1,341 @@
+// WebAssemblyMCInstLower.cpp - Convert WebAssembly MachineInstr to an MCInst //
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// 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 "MCTargetDesc/WebAssemblyMCTargetDesc.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/MCSymbolWasm.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+// Defines llvm::WebAssembly::getStackOpcode to convert register instructions to
+// stack instructions
+#define GET_INSTRMAP_INFO 1
+#include "WebAssemblyGenInstrInfo.inc"
+
+// This disables the removal of registers when lowering into MC, as required
+// by some current tests.
+cl::opt<bool>
+    WasmKeepRegisters("wasm-keep-registers", cl::Hidden,
+                      cl::desc("WebAssembly: output stack registers in"
+                               " instruction output for test purposes only."),
+                      cl::init(false));
+
+static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI);
+
+MCSymbol *
+WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
+  const GlobalValue *Global = MO.getGlobal();
+  auto *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global));
+
+  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<MVT, 1> ResultMVTs;
+    SmallVector<MVT, 4> ParamMVTs;
+    computeSignatureVTs(FuncTy, CurrentFunc, TM, ParamMVTs, ResultMVTs);
+
+    auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs);
+    WasmSym->setSignature(Signature.get());
+    Printer.addSignature(std::move(Signature));
+    WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
+  }
+
+  return WasmSym;
+}
+
+MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
+    const MachineOperand &MO) const {
+  const char *Name = MO.getSymbolName();
+  auto *WasmSym = cast<MCSymbolWasm>(Printer.GetExternalSymbolSymbol(Name));
+  const WebAssemblySubtarget &Subtarget = Printer.getSubtarget();
+
+  // Except for certain known symbols, all 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 || strcmp(Name, "__tls_base") == 0 ||
+      strcmp(Name, "__memory_base") == 0 || strcmp(Name, "__table_base") == 0 ||
+      strcmp(Name, "__tls_size") == 0 || strcmp(Name, "__tls_align") == 0) {
+    bool Mutable =
+        strcmp(Name, "__stack_pointer") == 0 || strcmp(Name, "__tls_base") == 0;
+    WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
+    WasmSym->setGlobalType(wasm::WasmGlobalType{
+        uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64
+                                      : wasm::WASM_TYPE_I32),
+        Mutable});
+    return WasmSym;
+  }
+
+  SmallVector<wasm::ValType, 4> Returns;
+  SmallVector<wasm::ValType, 4> Params;
+  if (strcmp(Name, "__cpp_exception") == 0) {
+    WasmSym->setType(wasm::WASM_SYMBOL_TYPE_EVENT);
+    // We can't confirm its signature index for now because there can be
+    // imported exceptions. Set it to be 0 for now.
+    WasmSym->setEventType(
+        {wasm::WASM_EVENT_ATTRIBUTE_EXCEPTION, /* SigIndex */ 0});
+    // We may have multiple C++ compilation units to be linked together, each of
+    // which defines the exception symbol. To resolve them, we declare them as
+    // weak.
+    WasmSym->setWeak(true);
+    WasmSym->setExternal(true);
+
+    // All C++ exceptions are assumed to have a single i32 (for wasm32) or i64
+    // (for wasm64) param type and void return type. The reaon is, all C++
+    // exception values are pointers, and to share the type section with
+    // functions, exceptions are assumed to have void return type.
+    Params.push_back(Subtarget.hasAddr64() ? wasm::ValType::I64
+                                           : wasm::ValType::I32);
+  } else { // Function symbols
+    WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
+    getLibcallSignature(Subtarget, Name, Returns, Params);
+  }
+  auto Signature =
+      std::make_unique<wasm::WasmSignature>(std::move(Returns), std::move(Params));
+  WasmSym->setSignature(Signature.get());
+  Printer.addSignature(std::move(Signature));
+
+  return WasmSym;
+}
+
+MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
+                                                     MCSymbol *Sym) const {
+  MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
+  unsigned TargetFlags = MO.getTargetFlags();
+
+  switch (TargetFlags) {
+    case WebAssemblyII::MO_NO_FLAG:
+      break;
+    case WebAssemblyII::MO_GOT:
+      Kind = MCSymbolRefExpr::VK_GOT;
+      break;
+    case WebAssemblyII::MO_MEMORY_BASE_REL:
+      Kind = MCSymbolRefExpr::VK_WASM_MBREL;
+      break;
+    case WebAssemblyII::MO_TABLE_BASE_REL:
+      Kind = MCSymbolRefExpr::VK_WASM_TBREL;
+      break;
+    default:
+      llvm_unreachable("Unknown target flag on GV operand");
+  }
+
+  const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx);
+
+  if (MO.getOffset() != 0) {
+    const auto *WasmSym = cast<MCSymbolWasm>(Sym);
+    if (TargetFlags == WebAssemblyII::MO_GOT)
+      report_fatal_error("GOT symbol references do not support offsets");
+    if (WasmSym->isFunction())
+      report_fatal_error("Function addresses with offsets not supported");
+    if (WasmSym->isGlobal())
+      report_fatal_error("Global indexes with offsets not supported");
+    if (WasmSym->isEvent())
+      report_fatal_error("Event indexes with offsets not supported");
+
+    Expr = MCBinaryExpr::createAdd(
+        Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
+  }
+
+  return MCOperand::createExpr(Expr);
+}
+
+MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand(
+    SmallVector<wasm::ValType, 1> &&Returns,
+    SmallVector<wasm::ValType, 4> &&Params) const {
+  auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
+                                                         std::move(Params));
+  MCSymbol *Sym = Printer.createTempSymbol("typeindex");
+  auto *WasmSym = cast<MCSymbolWasm>(Sym);
+  WasmSym->setSignature(Signature.get());
+  Printer.addSignature(std::move(Signature));
+  WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
+  const MCExpr *Expr =
+      MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, 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;
+  if (RC == &WebAssembly::V128RegClass)
+    return wasm::ValType::V128;
+  llvm_unreachable("Unexpected register class");
+}
+
+static void getFunctionReturns(const MachineInstr *MI,
+                               SmallVectorImpl<wasm::ValType> &Returns) {
+  const Function &F = MI->getMF()->getFunction();
+  const TargetMachine &TM = MI->getMF()->getTarget();
+  Type *RetTy = F.getReturnType();
+  SmallVector<MVT, 4> CallerRetTys;
+  computeLegalValueVTs(F, TM, RetTy, CallerRetTys);
+  valTypesFromMVTs(CallerRetTys, Returns);
+}
+
+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) {
+          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->getOpcode()))
+            Params.pop_back();
+
+          // return_call_indirect instructions have the return type of the
+          // caller
+          if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT)
+            getFunctionReturns(MI, Returns);
+
+          MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params));
+          break;
+        } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
+          auto BT = static_cast<WebAssembly::BlockType>(MO.getImm());
+          assert(BT != WebAssembly::BlockType::Invalid);
+          if (BT == WebAssembly::BlockType::Multivalue) {
+            SmallVector<wasm::ValType, 1> Returns;
+            getFunctionReturns(MI, Returns);
+            MCOp = lowerTypeIndexOperand(std::move(Returns),
+                                         SmallVector<wasm::ValType, 4>());
+            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:
+      MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
+      break;
+    case MachineOperand::MO_ExternalSymbol:
+      // The target flag indicates whether this is a symbol for a
+      // variable or a function.
+      assert(MO.getTargetFlags() == 0 &&
+             "WebAssembly uses only symbol flags on ExternalSymbols");
+      MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
+      break;
+    case MachineOperand::MO_MCSymbol:
+      // This is currently used only for LSDA symbols (GCC_except_table),
+      // because global addresses or other external symbols are handled above.
+      assert(MO.getTargetFlags() == 0 &&
+             "WebAssembly does not use target flags on MCSymbol");
+      MCOp = lowerSymbolOperand(MO, MO.getMCSymbol());
+      break;
+    }
+
+    OutMI.addOperand(MCOp);
+  }
+
+  if (!WasmKeepRegisters)
+    removeRegisterOperands(MI, OutMI);
+}
+
+static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) {
+  // Remove all uses of stackified registers to bring the instruction format
+  // into its final stack form used thruout MC, and transition opcodes to
+  // their _S variant.
+  // We do this seperate from the above code that still may need these
+  // registers for e.g. call_indirect signatures.
+  // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for
+  // details.
+  // TODO: the code above creates new registers which are then removed here.
+  // That code could be slightly simplified by not doing that, though maybe
+  // it is simpler conceptually to keep the code above in "register mode"
+  // until this transition point.
+  // FIXME: we are not processing inline assembly, which contains register
+  // operands, because it is used by later target generic code.
+  if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm())
+    return;
+
+  // Transform to _S instruction.
+  auto RegOpcode = OutMI.getOpcode();
+  auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode);
+  assert(StackOpcode != -1 && "Failed to stackify instruction");
+  OutMI.setOpcode(StackOpcode);
+
+  // Remove register operands.
+  for (auto I = OutMI.getNumOperands(); I; --I) {
+    auto &MO = OutMI.getOperand(I - 1);
+    if (MO.isReg()) {
+      OutMI.erase(&MO);
+    }
+  }
+}