Ryan Macnak
3dba3a77c1
When setting a breakpoint at a fast Smi op, replace the fast Smi op instruction with a Nop so we don't skip the following DebugBreak in the Smi case and don't attempt to increment an ICData counter through pool slot 0. R=zra@google.com Review URL: https://codereview.chromium.org/2194493002 .
109 lines
3.2 KiB
C++
109 lines
3.2 KiB
C++
// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#include "vm/globals.h"
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#if defined(TARGET_ARCH_DBC)
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#include "vm/code_patcher.h"
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#include "vm/cpu.h"
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#include "vm/debugger.h"
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#include "vm/instructions.h"
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#include "vm/stub_code.h"
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namespace dart {
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#ifndef PRODUCT
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RawCode* CodeBreakpoint::OrigStubAddress() const {
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return reinterpret_cast<RawCode*>(static_cast<uintptr_t>(saved_value_));
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}
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static Instr* CallInstructionFromReturnAddress(uword pc) {
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return reinterpret_cast<Instr*>(pc) - 1;
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}
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static Instr* FastSmiInstructionFromReturnAddress(uword pc) {
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return reinterpret_cast<Instr*>(pc) - 2;
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}
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void CodeBreakpoint::PatchCode() {
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ASSERT(!is_enabled_);
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const Code& code = Code::Handle(code_);
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const Instructions& instrs = Instructions::Handle(code.instructions());
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{
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WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
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saved_value_ = *CallInstructionFromReturnAddress(pc_);
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switch (breakpoint_kind_) {
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case RawPcDescriptors::kIcCall:
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case RawPcDescriptors::kUnoptStaticCall: {
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// DebugBreak has an A operand matching the call it replaces.
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// This ensures that Return instructions continue to work - as they
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// look at calls to figure out how many arguments to drop.
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*CallInstructionFromReturnAddress(pc_) =
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Bytecode::Encode(Bytecode::kDebugBreak,
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Bytecode::DecodeArgc(saved_value_),
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0,
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0);
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break;
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}
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case RawPcDescriptors::kRuntimeCall: {
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*CallInstructionFromReturnAddress(pc_) = Bytecode::kDebugBreak;
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break;
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}
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default:
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UNREACHABLE();
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}
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// If this call is the fall-through for a fast Smi op, also disable the fast
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// Smi op.
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if ((Bytecode::DecodeOpcode(saved_value_) == Bytecode::kInstanceCall2) &&
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Bytecode::IsFastSmiOpcode(*FastSmiInstructionFromReturnAddress(pc_))) {
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saved_value_fastsmi_ = *FastSmiInstructionFromReturnAddress(pc_);
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*FastSmiInstructionFromReturnAddress(pc_) =
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Bytecode::Encode(Bytecode::kNop, 0, 0, 0);
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} else {
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saved_value_fastsmi_ = Bytecode::kTrap;
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}
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}
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is_enabled_ = true;
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}
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void CodeBreakpoint::RestoreCode() {
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ASSERT(is_enabled_);
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const Code& code = Code::Handle(code_);
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const Instructions& instrs = Instructions::Handle(code.instructions());
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{
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WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
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switch (breakpoint_kind_) {
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case RawPcDescriptors::kIcCall:
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case RawPcDescriptors::kUnoptStaticCall:
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case RawPcDescriptors::kRuntimeCall: {
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*CallInstructionFromReturnAddress(pc_) = saved_value_;
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break;
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}
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default:
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UNREACHABLE();
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}
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if (saved_value_fastsmi_ != Bytecode::kTrap) {
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Instr current_instr = *FastSmiInstructionFromReturnAddress(pc_);
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ASSERT(Bytecode::DecodeOpcode(current_instr) == Bytecode::kNop);
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*FastSmiInstructionFromReturnAddress(pc_) = saved_value_fastsmi_;
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}
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}
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is_enabled_ = false;
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}
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#endif // !PRODUCT
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} // namespace dart
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#endif // defined TARGET_ARCH_DBC
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