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rustc_codegen_ssa: only create backend BasicBlocks as-needed.

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This commit is contained in:
Eduard-Mihai Burtescu 2021-05-06 17:37:19 +03:00
parent 7dc9ff5c62
commit 402e9efc56
7 changed files with 50 additions and 51 deletions
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52
compiler/rustc_codegen_ssa/src/mir/mod.rs
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@ -40,8 +40,11 @@ pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
/// then later loaded when generating the DIVERGE_BLOCK.
personality_slot: Option<PlaceRef<'tcx, Bx::Value>>,
/// A `Block` for each MIR `BasicBlock`
blocks: IndexVec<mir::BasicBlock, Bx::BasicBlock>,
/// A backend `BasicBlock` for each MIR `BasicBlock`, created lazily
/// as-needed (e.g. RPO reaching it or another block branching to it).
// FIXME(eddyb) rename `llbbs` and other `ll`-prefixed things to use a
// more backend-agnostic prefix such as `cg` (i.e. this would be `cgbbs`).
cached_llbbs: IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>>,
/// The funclet status of each basic block
cleanup_kinds: IndexVec<mir::BasicBlock, analyze::CleanupKind>,
@ -151,17 +154,17 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
// 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 block_bxs: IndexVec<mir::BasicBlock, Bx::BasicBlock> = mir
.basic_blocks()
.indices()
.map(|bb| {
if bb == mir::START_BLOCK && !reentrant_start_block {
bx.llbb()
} else {
bx.build_sibling_block(&format!("{:?}", bb)).llbb()
}
})
.collect();
let cached_llbbs: IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>> =
mir.basic_blocks()
.indices()
.map(|bb| {
if bb == mir::START_BLOCK && !reentrant_start_block {
Some(bx.llbb())
} else {
None
}
})
.collect();
let mut fx = FunctionCx {
instance,
@ -170,7 +173,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
fn_abi,
cx,
personality_slot: None,
blocks: block_bxs,
cached_llbbs,
unreachable_block: None,
cleanup_kinds,
landing_pads: IndexVec::from_elem(None, mir.basic_blocks()),
@ -245,29 +248,14 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
// Branch to the START block, if it's not the entry block.
if reentrant_start_block {
bx.br(fx.blocks[mir::START_BLOCK]);
bx.br(fx.llbb(mir::START_BLOCK));
}
let rpo = traversal::reverse_postorder(&mir);
let mut visited = BitSet::new_empty(mir.basic_blocks().len());
// Codegen the body of each block using reverse postorder
for (bb, _) in rpo {
visited.insert(bb.index());
// FIXME(eddyb) reuse RPO iterator between `analysis` and this.
for (bb, _) in traversal::reverse_postorder(&mir) {
fx.codegen_block(bb);
}
// Remove blocks that haven't been visited, or have no
// predecessors.
for bb in mir.basic_blocks().indices() {
// Unreachable block
if !visited.contains(bb.index()) {
debug!("codegen_mir: block {:?} was not visited", bb);
unsafe {
bx.delete_basic_block(fx.blocks[bb]);
}
}
}
}
/// Produces, for each argument, a `Value` pointing at the