Ryan Macnak
7ff2dd4117
The call sequence is very similar to a classic IC call, except the guarded class and the target are loaded indirectly from the constant pool instead of as immediates. In the monomorphic case, we call directly to the expected target with a class check in the callee. In the unlinked, polymorphic and megamorphic cases, we call a stub; these case are now call-through instead of call-and-return. Every code, except stubs involved in switchable calls, includes the class check sequence at the beginning. So we now distinguish between a checked and an unchecked entry point. Generated code except the switchable call continues to use the unchecked entry point. PC offsets are calculated relative to the beginning of the instruction stream, rather than either entry point. BUG= R=fschneider@google.com Review URL: https://codereview.chromium.org/2226893002 .
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.PayloadStart(), 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.PayloadStart(), 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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