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Eliminate a temporary heap allocation when splitting a critical edge.

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This commit is contained in:
Dan Gohman
2017-09-01 12:50:51 -07:00
parent d4c53935b4
commit 8237893113
1 changed files with 4 additions and 13 deletions
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17
lib/frontend/src/ssa.rs
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@@ -539,24 +539,15 @@ where
// In the case of a jump table, the situation is tricky because br_table doesn't // In the case of a jump table, the situation is tricky because br_table doesn't
// support arguments. // support arguments.
// We have to split the critical edge // We have to split the critical edge
let indexes: Vec<usize> = jts[jt].entries().fold(
Vec::new(),
|mut acc, (index, dest)| if dest ==
dest_ebb
{
acc.push(index);
acc
} else {
acc
},
);
let middle_ebb = dfg.make_ebb(); let middle_ebb = dfg.make_ebb();
layout.append_ebb(middle_ebb); layout.append_ebb(middle_ebb);
let block = self.declare_ebb_header_block(middle_ebb); let block = self.declare_ebb_header_block(middle_ebb);
self.blocks[block].add_predecessor(jump_inst_block, jump_inst); self.blocks[block].add_predecessor(jump_inst_block, jump_inst);
self.seal_ebb_header_block(middle_ebb, dfg, layout, jts); self.seal_ebb_header_block(middle_ebb, dfg, layout, jts);
for index in indexes { for old_dest in jts[jt].as_mut_slice() {
jts[jt].set_entry(index, middle_ebb) if old_dest.unwrap() == dest_ebb {
*old_dest = PackedOption::from(middle_ebb);
}
} }
let mut cur = Cursor::new(layout); let mut cur = Cursor::new(layout);
cur.goto_bottom(middle_ebb); cur.goto_bottom(middle_ebb);