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Compute reachable locals as part of non_ssa_locals

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This commit is contained in:
Ben Kimock 2024-08-24 21:03:38 -04:00
parent 0ea5dc506f
commit 523f8f8398
6 changed files with 79 additions and 112 deletions
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12
compiler/rustc_codegen_ssa/src/mir/mod.rs
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@ -192,9 +192,6 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
})
.collect();
let (traversal_order, reachable_locals) =
traversal::mono_reachable_reverse_postorder(mir, cx.tcx(), instance);
let mut fx = FunctionCx {
instance,
mir,
@ -221,7 +218,8 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info(&mut start_bx);
let memory_locals = analyze::non_ssa_locals(&fx, &traversal_order, &reachable_locals);
let traversal_order = traversal::mono_reachable_reverse_postorder(mir, cx.tcx(), instance);
let memory_locals = analyze::non_ssa_locals(&fx, &traversal_order);
// Allocate variable and temp allocas
let local_values = {
@ -286,6 +284,12 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
fx.codegen_block(bb);
unreached_blocks.remove(bb);
}
// FIXME: These empty unreachable blocks are *mostly* a waste. They are occasionally
// targets for a SwitchInt terminator, but the reimplementation of the mono-reachable
// simplification in SwitchInt lowering sometimes misses cases that
// mono_reachable_reverse_postorder manages to figure out.
// The solution is to do something like post-mono GVN. But for now we have this hack.
for bb in unreached_blocks.iter() {
fx.codegen_block_as_unreachable(bb);
}