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ladybird/Userland/Libraries/LibJS/Bytecode/Label.h

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LibJS: Add basic support for while loops in the bytecode engine This introduces two new instructions: Jump and JumpIfFalse. Jumps are made to a Bytecode::Label, which is a simple object that represents a location in the bytecode stream. Note that you may not always know the target of a jump when adding the jump instruction itself, but we can just update the instruction later on during codegen once we know where the jump target is. The Bytecode::Interpreter now implements jumping via a jump slot that gets checked after each instruction to see if a jump is pending. If not, we just increment the PC as usual.
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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Format.h>
LibJS: Generate bytecode in basic blocks instead of one big block This limits the size of each block (currently set to 1K), and gets us closer to a canonical, more easily analysable bytecode format. As a result of this, "Labels" are now simply entries to basic blocks. Since there is no more 'conditional' jump (as all jumps are always taken), JumpIf{True,False} are unified to JumpConditional, and JumpIfNullish is renamed to JumpNullish. Also fixes #7914 as a result of reimplementing the loop logic.
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#include <LibJS/Bytecode/BasicBlock.h>
LibJS: Add basic support for while loops in the bytecode engine This introduces two new instructions: Jump and JumpIfFalse. Jumps are made to a Bytecode::Label, which is a simple object that represents a location in the bytecode stream. Note that you may not always know the target of a jump when adding the jump instruction itself, but we can just update the instruction later on during codegen once we know where the jump target is. The Bytecode::Interpreter now implements jumping via a jump slot that gets checked after each instruction to see if a jump is pending. If not, we just increment the PC as usual.
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namespace JS::Bytecode {
class Label {
public:
LibJS: Generate bytecode in basic blocks instead of one big block This limits the size of each block (currently set to 1K), and gets us closer to a canonical, more easily analysable bytecode format. As a result of this, "Labels" are now simply entries to basic blocks. Since there is no more 'conditional' jump (as all jumps are always taken), JumpIf{True,False} are unified to JumpConditional, and JumpIfNullish is renamed to JumpNullish. Also fixes #7914 as a result of reimplementing the loop logic.
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explicit Label(BasicBlock const& block)
LibJS: Add a basic pass manager and add some basic passes This commit adds a bunch of passes, the most interesting of which is a pass that merges blocks together, and a pass that places blocks that flow into each other next to each other, and a very simply pass that removes duplicate basic blocks. Note that this does not remove the jump at the end of each block in that pass to avoid scope creep in the passes.
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: m_block(&block)
LibJS: Add basic support for while loops in the bytecode engine This introduces two new instructions: Jump and JumpIfFalse. Jumps are made to a Bytecode::Label, which is a simple object that represents a location in the bytecode stream. Note that you may not always know the target of a jump when adding the jump instruction itself, but we can just update the instruction later on during codegen once we know where the jump target is. The Bytecode::Interpreter now implements jumping via a jump slot that gets checked after each instruction to see if a jump is pending. If not, we just increment the PC as usual.
2021-06-04 12:07:38 +02:00
{
}
LibJS/Bytecode: Flatten bytecode to a contiguous representation Instead of keeping bytecode as a set of disjoint basic blocks on the malloc heap, bytecode is now a contiguous sequence of bytes(!) The transformation happens at the end of Bytecode::Generator::generate() and the only really hairy part is rerouting jump labels. This required solving a few problems: - The interpreter execution loop had to change quite a bit, since we were storing BasicBlock pointers all over the place, and control transfer was done by redirecting the interpreter's current block. - Exception handlers & finalizers are now stored per-bytecode-range in a side table in Executable. - The interpreter now has a plain program counter instead of a stream iterator. This actually makes error stack generation a bit nicer since we just have to deal with a number instead of reaching into the iterator. This yields a 25% performance improvement on this microbenchmark: for (let i = 0; i < 1_000_000; ++i) { } But basically everything gets faster. :^)
2024-05-06 06:44:08 +02:00
// Used while compiling.
BasicBlock const& block() const { return *m_block; }
// Used after compiling.
size_t address() const { return m_address; }
void set_address(size_t address) { m_address = address; }
LibJS: Add basic support for while loops in the bytecode engine This introduces two new instructions: Jump and JumpIfFalse. Jumps are made to a Bytecode::Label, which is a simple object that represents a location in the bytecode stream. Note that you may not always know the target of a jump when adding the jump instruction itself, but we can just update the instruction later on during codegen once we know where the jump target is. The Bytecode::Interpreter now implements jumping via a jump slot that gets checked after each instruction to see if a jump is pending. If not, we just increment the PC as usual.
2021-06-04 12:07:38 +02:00
private:
LibJS/Bytecode: Flatten bytecode to a contiguous representation Instead of keeping bytecode as a set of disjoint basic blocks on the malloc heap, bytecode is now a contiguous sequence of bytes(!) The transformation happens at the end of Bytecode::Generator::generate() and the only really hairy part is rerouting jump labels. This required solving a few problems: - The interpreter execution loop had to change quite a bit, since we were storing BasicBlock pointers all over the place, and control transfer was done by redirecting the interpreter's current block. - Exception handlers & finalizers are now stored per-bytecode-range in a side table in Executable. - The interpreter now has a plain program counter instead of a stream iterator. This actually makes error stack generation a bit nicer since we just have to deal with a number instead of reaching into the iterator. This yields a 25% performance improvement on this microbenchmark: for (let i = 0; i < 1_000_000; ++i) { } But basically everything gets faster. :^)
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union {
// Relevant while compiling.
BasicBlock const* m_block { nullptr };
// Relevant after compiling.
size_t m_address;
};
LibJS: Add basic support for while loops in the bytecode engine This introduces two new instructions: Jump and JumpIfFalse. Jumps are made to a Bytecode::Label, which is a simple object that represents a location in the bytecode stream. Note that you may not always know the target of a jump when adding the jump instruction itself, but we can just update the instruction later on during codegen once we know where the jump target is. The Bytecode::Interpreter now implements jumping via a jump slot that gets checked after each instruction to see if a jump is pending. If not, we just increment the PC as usual.
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};
}
template<>
struct AK::Formatter<JS::Bytecode::Label> : AK::Formatter<FormatString> {
LibJS/Bytecode: Flatten bytecode to a contiguous representation Instead of keeping bytecode as a set of disjoint basic blocks on the malloc heap, bytecode is now a contiguous sequence of bytes(!) The transformation happens at the end of Bytecode::Generator::generate() and the only really hairy part is rerouting jump labels. This required solving a few problems: - The interpreter execution loop had to change quite a bit, since we were storing BasicBlock pointers all over the place, and control transfer was done by redirecting the interpreter's current block. - Exception handlers & finalizers are now stored per-bytecode-range in a side table in Executable. - The interpreter now has a plain program counter instead of a stream iterator. This actually makes error stack generation a bit nicer since we just have to deal with a number instead of reaching into the iterator. This yields a 25% performance improvement on this microbenchmark: for (let i = 0; i < 1_000_000; ++i) { } But basically everything gets faster. :^)
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ErrorOr<void> format(FormatBuilder& builder, JS::Bytecode::Label const& label)
LibJS: Add basic support for while loops in the bytecode engine This introduces two new instructions: Jump and JumpIfFalse. Jumps are made to a Bytecode::Label, which is a simple object that represents a location in the bytecode stream. Note that you may not always know the target of a jump when adding the jump instruction itself, but we can just update the instruction later on during codegen once we know where the jump target is. The Bytecode::Interpreter now implements jumping via a jump slot that gets checked after each instruction to see if a jump is pending. If not, we just increment the PC as usual.
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{
LibJS/Bytecode: Flatten bytecode to a contiguous representation Instead of keeping bytecode as a set of disjoint basic blocks on the malloc heap, bytecode is now a contiguous sequence of bytes(!) The transformation happens at the end of Bytecode::Generator::generate() and the only really hairy part is rerouting jump labels. This required solving a few problems: - The interpreter execution loop had to change quite a bit, since we were storing BasicBlock pointers all over the place, and control transfer was done by redirecting the interpreter's current block. - Exception handlers & finalizers are now stored per-bytecode-range in a side table in Executable. - The interpreter now has a plain program counter instead of a stream iterator. This actually makes error stack generation a bit nicer since we just have to deal with a number instead of reaching into the iterator. This yields a 25% performance improvement on this microbenchmark: for (let i = 0; i < 1_000_000; ++i) { } But basically everything gets faster. :^)
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return AK::Formatter<FormatString>::format(builder, "@{:x}"sv, label.address());
LibJS: Add basic support for while loops in the bytecode engine This introduces two new instructions: Jump and JumpIfFalse. Jumps are made to a Bytecode::Label, which is a simple object that represents a location in the bytecode stream. Note that you may not always know the target of a jump when adding the jump instruction itself, but we can just update the instruction later on during codegen once we know where the jump target is. The Bytecode::Interpreter now implements jumping via a jump slot that gets checked after each instruction to see if a jump is pending. If not, we just increment the PC as usual.
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}
};
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