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Additional comments for lowering if

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This commit is contained in:
Zalathar 2024-03-06 15:22:39 +11:00
parent 3402f39bcb
commit 250e697834
1 changed files with 8 additions and 0 deletions
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8
compiler/rustc_mir_build/src/build/expr/into.rs
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@ -66,6 +66,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
(if_then_scope, then_source_info), (if_then_scope, then_source_info),
LintLevel::Inherited, LintLevel::Inherited,
|this| { |this| {
// FIXME: Does this need extra logic to handle let-chains?
let source_info = if this.is_let(cond) { let source_info = if this.is_let(cond) {
let variable_scope = let variable_scope =
this.new_source_scope(then_span, LintLevel::Inherited, None); this.new_source_scope(then_span, LintLevel::Inherited, None);
@ -74,6 +75,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
} else { } else {
this.source_info(then_span) this.source_info(then_span)
}; };
// Lower the condition, and have it branch into `then` and `else` blocks.
let (then_block, else_block) = let (then_block, else_block) =
this.in_if_then_scope(condition_scope, then_span, |this| { this.in_if_then_scope(condition_scope, then_span, |this| {
let then_blk = unpack!(this.then_else_break( let then_blk = unpack!(this.then_else_break(
@ -85,8 +88,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
true, // Declare `let` bindings normally true, // Declare `let` bindings normally
)); ));
// Lower the `then` arm into its block.
this.expr_into_dest(destination, then_blk, then) this.expr_into_dest(destination, then_blk, then)
}); });
// Pack `(then_block, else_block)` into `BlockAnd<BasicBlock>`.
then_block.and(else_block) then_block.and(else_block)
}, },
); );
@ -105,6 +111,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
this.cfg.push_assign_unit(else_blk, correct_si, destination, this.tcx); this.cfg.push_assign_unit(else_blk, correct_si, destination, this.tcx);
} }
// The `then` and `else` arms have been lowered into their respective
// blocks, so make both of them meet up in a new block.
let join_block = this.cfg.start_new_block(); let join_block = this.cfg.start_new_block();
this.cfg.goto(then_blk, source_info, join_block); this.cfg.goto(then_blk, source_info, join_block);
this.cfg.goto(else_blk, source_info, join_block); this.cfg.goto(else_blk, source_info, join_block);