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https://github.com/carbon-language/carbon-lang.git
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Jon Ross-Perkins
77d38a8350
This is something we'd discussed. I added a TODO that we may want to eventually make this a map, but I remain uncertain and think it's not something that's going to really cost us if we end up switching back. In the meantime, I think this approach does offer simplicity. As discussed too, the performance overhead of a map may ultimately not be worthwhile here versus the relative memory costs.
67 lines
2.4 KiB
C++
67 lines
2.4 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#ifndef CARBON_TOOLCHAIN_LOWERING_LOWERING_H_
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#define CARBON_TOOLCHAIN_LOWERING_LOWERING_H_
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "toolchain/semantics/semantics_ir.h"
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#include "toolchain/semantics/semantics_node.h"
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namespace Carbon {
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// Use LowerToLLVM rather than calling this directly.
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//
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// This carries state for lowering. `Run()` should only be called once, and
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// handles the main execution.
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class Lowering {
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public:
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explicit Lowering(llvm::LLVMContext& llvm_context,
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llvm::StringRef module_name,
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const SemanticsIR& semantics_ir);
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// Lowers the SemanticsIR to LLVM IR.
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auto Run() -> std::unique_ptr<llvm::Module>;
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private:
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// Declare handlers for each SemanticsIR node.
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#define CARBON_SEMANTICS_NODE_KIND(Name) \
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auto Handle##Name##Node(SemanticsNodeId node_id, SemanticsNode node)->void;
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#include "toolchain/semantics/semantics_node_kind.def"
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// Runs lowering for a block.
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auto LowerBlock(SemanticsNodeBlockId block_id) -> void;
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// Returns a type for the given node.
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auto LowerNodeToType(SemanticsNodeId node_id) -> llvm::Type*;
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// State for building the LLVM IR.
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llvm::LLVMContext* llvm_context_;
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std::unique_ptr<llvm::Module> llvm_module_;
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llvm::IRBuilder<> builder_;
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// The input Semantics IR.
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const SemanticsIR* const semantics_ir_;
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// Blocks which we've observed and need to lower.
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llvm::SmallVector<std::pair<llvm::BasicBlock*, SemanticsNodeBlockId>>
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todo_blocks_;
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// Maps nodes in SemanticsIR to a lowered value. This will have one entry per
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// node, and will be non-null when lowered. It's expected to be sparse during
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// execution because while expressions will have entries, statements won't.
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// TODO: This will probably become a PointerUnion of Value and Type.
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// TODO: Long-term, we should examine the practical trade-offs of making this
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// a map; a map may end up lower memory consumption, but a vector offers cache
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// efficiency and better performance. As a consequence, the right choice is
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// unclear.
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llvm::SmallVector<llvm::Value*> lowered_nodes_;
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};
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} // namespace Carbon
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#endif // CARBON_TOOLCHAIN_LOWERING_LOWERING_H_
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