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Remove support for reentrant start blocks from codegen

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The start block is guaranteed not to have any basic block predecessors.
This commit is contained in:
Tomasz Miąsko 2021-09-14 00:00:00 +00:00
parent 4d614e1d1f
commit 3489ba3bbb
1 changed files with 5 additions and 19 deletions
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20
compiler/rustc_codegen_ssa/src/mir/mod.rs
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@ -152,19 +152,10 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
}
let cleanup_kinds = analyze::cleanup_kinds(&mir);
// Allocate a `Block` for every basic block, except
// the start block, if nothing loops back to it.
let reentrant_start_block = !mir.predecessors()[mir::START_BLOCK].is_empty();
let cached_llbbs: IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>> =
mir.basic_blocks()
let cached_llbbs: IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>> = mir
.basic_blocks()
.indices()
.map(|bb| {
if bb == mir::START_BLOCK && !reentrant_start_block {
Some(start_llbb)
} else {
None
}
})
.map(|bb| if bb == mir::START_BLOCK { Some(start_llbb) } else { None })
.collect();
let mut fx = FunctionCx {
@ -247,11 +238,6 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
// Apply debuginfo to the newly allocated locals.
fx.debug_introduce_locals(&mut bx);
// Branch to the START block, if it's not the entry block.
if reentrant_start_block {
bx.br(fx.llbb(mir::START_BLOCK));
}
// Codegen the body of each block using reverse postorder
// FIXME(eddyb) reuse RPO iterator between `analysis` and this.
for (bb, _) in traversal::reverse_postorder(&mir) {