mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-29 17:34:58 +01:00
Richard Smith
202d3f5993
Add semantic analysis and semantics IR building for `if` expressions, and add the first parts of control flow handling to semantics IR. After discussion with @chandlerc, use [block arguments](https://en.wikipedia.org/wiki/Static_single-assignment_form#Block_arguments) to convey values from the two arms of the `if` to the result. For now, only a single block argument is supported, but we should revisit this as we explore more of the requirements of the Semantics IR form. Functions can now contain multiple code blocks, so grab the entry block up-front instead of assuming the entry block will be at the top of the block stack when we reach the end of function emission. Add trivial support for `bool` type literal, because without it we can't write testcases.
78 lines
3.2 KiB
C++
78 lines
3.2 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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#include "toolchain/semantics/semantics_context.h"
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namespace Carbon {
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auto SemanticsHandleIfExpressionIf(SemanticsContext& context,
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ParseTree::Node if_node) -> bool {
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auto cond_value_id = context.node_stack().Pop<SemanticsNodeId>();
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context.node_stack().Push(if_node);
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// Convert the condition to `bool`.
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cond_value_id = context.ImplicitAsRequired(
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if_node, cond_value_id,
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context.CanonicalizeType(SemanticsNodeId::BuiltinBoolType));
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// Stop emitting the current block. We'll add some branch instructions to it
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// later, but we don't want it on the stack any more.
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auto if_block_id = context.node_block_stack().PeekForAdd();
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context.node_block_stack().Pop();
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// Create the resumption block, `else` block, and `then` block, and branches
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// to them.
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context.node_block_stack().Push();
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auto else_block_id = context.node_block_stack().PushForAdd();
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auto then_block_id = context.node_block_stack().PushForAdd();
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context.AddNodeToBlock(
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if_block_id,
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SemanticsNode::BranchIf::Make(if_node, then_block_id, cond_value_id));
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context.AddNodeToBlock(if_block_id,
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SemanticsNode::Branch::Make(if_node, else_block_id));
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return true;
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}
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auto SemanticsHandleIfExpressionThen(SemanticsContext& context,
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ParseTree::Node then_node) -> bool {
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context.node_stack().Push(then_node, context.node_block_stack().Pop());
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return true;
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}
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auto SemanticsHandleIfExpressionElse(SemanticsContext& context,
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ParseTree::Node else_node) -> bool {
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auto else_value_id = context.node_stack().Pop<SemanticsNodeId>();
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auto [then_node, then_end_block_id] =
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context.node_stack().PopWithParseNode<SemanticsNodeBlockId>(
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ParseNodeKind::IfExpressionThen);
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auto then_value_id = context.node_stack().Pop<SemanticsNodeId>();
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auto if_node =
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context.node_stack().PopForSoloParseNode(ParseNodeKind::IfExpressionIf);
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// Convert the `else` value to the `then` value's type, and finish the `else`
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// block.
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// TODO: Find a common type, and convert both operands to it instead.
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auto result_type_id = context.semantics_ir().GetNode(then_value_id).type_id();
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else_value_id =
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context.ImplicitAsRequired(else_node, else_value_id, result_type_id);
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auto else_end_block_id = context.node_block_stack().Pop();
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// Create branches to the resumption block.
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auto resume_block_id = context.node_block_stack().PeekForAdd();
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context.AddNodeToBlock(then_end_block_id,
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SemanticsNode::BranchWithArg::Make(
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then_node, resume_block_id, then_value_id));
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context.AddNodeToBlock(else_end_block_id,
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SemanticsNode::BranchWithArg::Make(
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else_node, resume_block_id, else_value_id));
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// Obtain the value in the resumption block and push it.
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context.AddNodeAndPush(
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if_node, SemanticsNode::BlockArg::Make(if_node, result_type_id));
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return true;
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}
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} // namespace Carbon
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