51 lines
2.3 KiB
Rust
51 lines
2.3 KiB
Rust
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use super::{BasicBlockId, ValueId};
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use crate::ast::{ASTNode, LiteralValue};
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impl super::MirBuilder {
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// Peek expression lowering
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pub(super) fn build_peek_expression(
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&mut self,
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scrutinee: ASTNode,
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arms: Vec<(LiteralValue, ASTNode)>,
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else_expr: ASTNode,
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) -> Result<ValueId, String> {
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let scr_val = self.build_expression_impl(scrutinee)?;
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let merge_block: BasicBlockId = self.block_gen.next();
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let result_val = self.value_gen.next();
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let mut phi_inputs: Vec<(BasicBlockId, ValueId)> = Vec::new();
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let mut next_block = self.block_gen.next();
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self.start_new_block(next_block)?;
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for (i, (label, arm_expr)) in arms.iter().cloned().enumerate() {
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let then_block = self.block_gen.next();
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// Only string labels handled here (behavior unchanged)
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if let LiteralValue::String(s) = label {
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let lit_id = self.value_gen.next();
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self.emit_instruction(super::MirInstruction::Const { dst: lit_id, value: super::ConstValue::String(s) })?;
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let cond_id = self.value_gen.next();
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self.emit_instruction(super::MirInstruction::Compare { dst: cond_id, op: super::CompareOp::Eq, lhs: scr_val, rhs: lit_id })?;
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self.emit_instruction(super::MirInstruction::Branch { condition: cond_id, then_bb: then_block, else_bb: next_block })?;
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self.start_new_block(then_block)?;
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let then_val = self.build_expression_impl(arm_expr)?;
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phi_inputs.push((then_block, then_val));
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self.emit_instruction(super::MirInstruction::Jump { target: merge_block })?;
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if i < arms.len() - 1 {
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let b = self.block_gen.next();
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self.start_new_block(b)?;
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next_block = b;
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}
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}
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}
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let else_block_id = next_block;
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self.start_new_block(else_block_id)?;
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let else_val = self.build_expression_impl(else_expr)?;
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phi_inputs.push((else_block_id, else_val));
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self.emit_instruction(super::MirInstruction::Jump { target: merge_block })?;
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self.start_new_block(merge_block)?;
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self.emit_instruction(super::MirInstruction::Phi { dst: result_val, inputs: phi_inputs })?;
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Ok(result_val)
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}
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}
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