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llvm-mirror/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp
Wouter van Oortmerssen 2d2a0b49b2 [WebAssembly] Add int32 DW_OP_WASM_location variant 
This to allow us to add reloctable global indices as a symbol.
Also adds R_WASM_GLOBAL_INDEX_I32 relocation type to support it.

See discussion in https://github.com/WebAssembly/debugging/issues/12
2020-04-16 16:32:17 -07:00

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//===-- WebAssemblyInstrInfo.cpp - WebAssembly Instruction Information ----===//
//
// 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 the WebAssembly implementation of the
/// TargetInstrInfo class.
///
//===----------------------------------------------------------------------===//
#include "WebAssemblyInstrInfo.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssembly.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-instr-info"
#define GET_INSTRINFO_CTOR_DTOR
#include "WebAssemblyGenInstrInfo.inc"
// defines WebAssembly::getNamedOperandIdx
#define GET_INSTRINFO_NAMED_OPS
#include "WebAssemblyGenInstrInfo.inc"
WebAssemblyInstrInfo::WebAssemblyInstrInfo(const WebAssemblySubtarget &STI)
: WebAssemblyGenInstrInfo(WebAssembly::ADJCALLSTACKDOWN,
WebAssembly::ADJCALLSTACKUP,
WebAssembly::CATCHRET),
RI(STI.getTargetTriple()) {}
bool WebAssemblyInstrInfo::isReallyTriviallyReMaterializable(
const MachineInstr &MI, AAResults *AA) const {
switch (MI.getOpcode()) {
case WebAssembly::CONST_I32:
case WebAssembly::CONST_I64:
case WebAssembly::CONST_F32:
case WebAssembly::CONST_F64:
// isReallyTriviallyReMaterializableGeneric misses these because of the
// ARGUMENTS implicit def, so we manualy override it here.
return true;
default:
return false;
}
}
void WebAssemblyInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
const DebugLoc &DL, MCRegister DestReg,
MCRegister SrcReg, bool KillSrc) const {
// This method is called by post-RA expansion, which expects only pregs to
// exist. However we need to handle both here.
auto &MRI = MBB.getParent()->getRegInfo();
const TargetRegisterClass *RC =
Register::isVirtualRegister(DestReg)
? MRI.getRegClass(DestReg)
: MRI.getTargetRegisterInfo()->getMinimalPhysRegClass(DestReg);
unsigned CopyOpcode;
if (RC == &WebAssembly::I32RegClass)
CopyOpcode = WebAssembly::COPY_I32;
else if (RC == &WebAssembly::I64RegClass)
CopyOpcode = WebAssembly::COPY_I64;
else if (RC == &WebAssembly::F32RegClass)
CopyOpcode = WebAssembly::COPY_F32;
else if (RC == &WebAssembly::F64RegClass)
CopyOpcode = WebAssembly::COPY_F64;
else if (RC == &WebAssembly::V128RegClass)
CopyOpcode = WebAssembly::COPY_V128;
else if (RC == &WebAssembly::EXNREFRegClass)
CopyOpcode = WebAssembly::COPY_EXNREF;
else
llvm_unreachable("Unexpected register class");
BuildMI(MBB, I, DL, get(CopyOpcode), DestReg)
.addReg(SrcReg, KillSrc ? RegState::Kill : 0);
}
MachineInstr *WebAssemblyInstrInfo::commuteInstructionImpl(
MachineInstr &MI, bool NewMI, unsigned OpIdx1, unsigned OpIdx2) const {
// If the operands are stackified, we can't reorder them.
WebAssemblyFunctionInfo &MFI =
*MI.getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
if (MFI.isVRegStackified(MI.getOperand(OpIdx1).getReg()) ||
MFI.isVRegStackified(MI.getOperand(OpIdx2).getReg()))
return nullptr;
// Otherwise use the default implementation.
return TargetInstrInfo::commuteInstructionImpl(MI, NewMI, OpIdx1, OpIdx2);
}
// Branch analysis.
bool WebAssemblyInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
MachineBasicBlock *&TBB,
MachineBasicBlock *&FBB,
SmallVectorImpl<MachineOperand> &Cond,
bool /*AllowModify*/) const {
const auto &MFI = *MBB.getParent()->getInfo<WebAssemblyFunctionInfo>();
// WebAssembly has control flow that doesn't have explicit branches or direct
// fallthrough (e.g. try/catch), which can't be modeled by analyzeBranch. It
// is created after CFGStackify.
if (MFI.isCFGStackified())
return true;
bool HaveCond = false;
for (MachineInstr &MI : MBB.terminators()) {
switch (MI.getOpcode()) {
default:
// Unhandled instruction; bail out.
return true;
case WebAssembly::BR_IF:
if (HaveCond)
return true;
Cond.push_back(MachineOperand::CreateImm(true));
Cond.push_back(MI.getOperand(1));
TBB = MI.getOperand(0).getMBB();
HaveCond = true;
break;
case WebAssembly::BR_UNLESS:
if (HaveCond)
return true;
Cond.push_back(MachineOperand::CreateImm(false));
Cond.push_back(MI.getOperand(1));
TBB = MI.getOperand(0).getMBB();
HaveCond = true;
break;
case WebAssembly::BR:
if (!HaveCond)
TBB = MI.getOperand(0).getMBB();
else
FBB = MI.getOperand(0).getMBB();
break;
case WebAssembly::BR_ON_EXN:
if (HaveCond)
return true;
Cond.push_back(MachineOperand::CreateImm(true));
Cond.push_back(MI.getOperand(2));
TBB = MI.getOperand(0).getMBB();
HaveCond = true;
break;
}
if (MI.isBarrier())
break;
}
return false;
}
unsigned WebAssemblyInstrInfo::removeBranch(MachineBasicBlock &MBB,
int *BytesRemoved) const {
assert(!BytesRemoved && "code size not handled");
MachineBasicBlock::instr_iterator I = MBB.instr_end();
unsigned Count = 0;
while (I != MBB.instr_begin()) {
--I;
if (I->isDebugInstr())
continue;
if (!I->isTerminator())
break;
// Remove the branch.
I->eraseFromParent();
I = MBB.instr_end();
++Count;
}
return Count;
}
unsigned WebAssemblyInstrInfo::insertBranch(
MachineBasicBlock &MBB, MachineBasicBlock *TBB, MachineBasicBlock *FBB,
ArrayRef<MachineOperand> Cond, const DebugLoc &DL, int *BytesAdded) const {
assert(!BytesAdded && "code size not handled");
if (Cond.empty()) {
if (!TBB)
return 0;
BuildMI(&MBB, DL, get(WebAssembly::BR)).addMBB(TBB);
return 1;
}
assert(Cond.size() == 2 && "Expected a flag and a successor block");
MachineFunction &MF = *MBB.getParent();
auto &MRI = MF.getRegInfo();
bool IsBrOnExn = Cond[1].isReg() && MRI.getRegClass(Cond[1].getReg()) ==
&WebAssembly::EXNREFRegClass;
if (Cond[0].getImm()) {
if (IsBrOnExn) {
const char *CPPExnSymbol = MF.createExternalSymbolName("__cpp_exception");
BuildMI(&MBB, DL, get(WebAssembly::BR_ON_EXN))
.addMBB(TBB)
.addExternalSymbol(CPPExnSymbol)
.add(Cond[1]);
} else
BuildMI(&MBB, DL, get(WebAssembly::BR_IF)).addMBB(TBB).add(Cond[1]);
} else {
assert(!IsBrOnExn && "br_on_exn does not have a reversed condition");
BuildMI(&MBB, DL, get(WebAssembly::BR_UNLESS)).addMBB(TBB).add(Cond[1]);
}
if (!FBB)
return 1;
BuildMI(&MBB, DL, get(WebAssembly::BR)).addMBB(FBB);
return 2;
}
bool WebAssemblyInstrInfo::reverseBranchCondition(
SmallVectorImpl<MachineOperand> &Cond) const {
assert(Cond.size() == 2 && "Expected a flag and a condition expression");
// br_on_exn's condition cannot be reversed
MachineFunction &MF = *Cond[1].getParent()->getParent()->getParent();
auto &MRI = MF.getRegInfo();
if (Cond[1].isReg() &&
MRI.getRegClass(Cond[1].getReg()) == &WebAssembly::EXNREFRegClass)
return true;
Cond.front() = MachineOperand::CreateImm(!Cond.front().getImm());
return false;
}
ArrayRef<std::pair<int, const char *>>
WebAssemblyInstrInfo::getSerializableTargetIndices() const {
static const std::pair<int, const char *> TargetIndices[] = {
{WebAssembly::TI_LOCAL, "wasm-local"},
{WebAssembly::TI_GLOBAL_FIXED, "wasm-global-fixed"},
{WebAssembly::TI_OPERAND_STACK, "wasm-operand-stack"},
{WebAssembly::TI_GLOBAL_RELOC, "wasm-global-reloc"}};
return makeArrayRef(TargetIndices);
}
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