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llvm-mirror/lib/Target/WebAssembly/WebAssemblyDebugValueManager.cpp
Heejin Ahn 9c4b79c3d5 [WebAssembly] Add NullifyDebugValueLists pass
`WebAssemblyDebugValueManager` does not currently handle
`DBG_VALUE_LIST`, which is a recent addition to LLVM. We tried to
nullify them within the constructor of `WebAssemblyDebugValueManager` in
D102589, but it made the class error-prone to use because it deletes
instructions within the constructor and thus invalidates existing
iterators within the BB, so the user of the class should take special
care not to use invalidated iterators. This actually caused a bug in
ExplicitLocals pass.

Instead of trying to fix ExplicitLocals pass to make the iterator usage
correct, which is possible but error-prone, this adds
NullifyDebugValueLists pass that nullifies all `DBG_VALUE_LIST`
instructions before we run WebAssembly specific passes in the backend.
We can remove this pass after we implement handlers for
`DBG_VALUE_LIST`s in `WebAssemblyDebugValueManager` and elsewhere.

Fixes https://github.com/emscripten-core/emscripten/issues/14255.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D102999
2021-05-24 11:36:01 -07:00

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2.5 KiB
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//===-- WebAssemblyDebugValueManager.cpp - WebAssembly DebugValue Manager -===//
//
// 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 implements the manager for MachineInstr DebugValues.
///
//===----------------------------------------------------------------------===//
#include "WebAssemblyDebugValueManager.h"
#include "WebAssembly.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
using namespace llvm;
WebAssemblyDebugValueManager::WebAssemblyDebugValueManager(
MachineInstr *Instr) {
// This code differs from MachineInstr::collectDebugValues in that it scans
// the whole BB, not just contiguous DBG_VALUEs.
if (!Instr->getOperand(0).isReg())
return;
CurrentReg = Instr->getOperand(0).getReg();
MachineBasicBlock::iterator DI = *Instr;
++DI;
for (MachineBasicBlock::iterator DE = Instr->getParent()->end(); DI != DE;
++DI) {
if (DI->isDebugValue() &&
DI->hasDebugOperandForReg(Instr->getOperand(0).getReg()))
DbgValues.push_back(&*DI);
}
}
void WebAssemblyDebugValueManager::move(MachineInstr *Insert) {
MachineBasicBlock *MBB = Insert->getParent();
for (MachineInstr *DBI : reverse(DbgValues))
MBB->splice(Insert, DBI->getParent(), DBI);
}
void WebAssemblyDebugValueManager::updateReg(unsigned Reg) {
for (auto *DBI : DbgValues)
for (auto &MO : DBI->getDebugOperandsForReg(CurrentReg))
MO.setReg(Reg);
CurrentReg = Reg;
}
void WebAssemblyDebugValueManager::clone(MachineInstr *Insert,
unsigned NewReg) {
MachineBasicBlock *MBB = Insert->getParent();
MachineFunction *MF = MBB->getParent();
for (MachineInstr *DBI : reverse(DbgValues)) {
MachineInstr *Clone = MF->CloneMachineInstr(DBI);
for (auto &MO : Clone->getDebugOperandsForReg(CurrentReg))
MO.setReg(NewReg);
MBB->insert(Insert, Clone);
}
}
void WebAssemblyDebugValueManager::replaceWithLocal(unsigned LocalId) {
for (auto *DBI : DbgValues) {
auto IndexType = DBI->isIndirectDebugValue()
? llvm::WebAssembly::TI_LOCAL_INDIRECT
: llvm::WebAssembly::TI_LOCAL;
for (auto &MO : DBI->getDebugOperandsForReg(CurrentReg))
MO.ChangeToTargetIndex(IndexType, LocalId);
}
}