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Move default blocks into jump tables (#5756)

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Move the default block off of the br_table instrution, and into the JumpTable that it references.
This commit is contained in:
Trevor Elliott
2023-02-10 08:53:30 -08:00
committed by GitHub
parent 49613be393
commit d99783fc91
21 changed files with 118 additions and 175 deletions
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19
cranelift/frontend/src/ssa.rs
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@@ -591,27 +591,18 @@ impl SSABuilder {
}
None
}
InstructionData::BranchTable {
table: jt,
destination,
..
} => {
InstructionData::BranchTable { table: jt, .. } => {
// In the case of a jump table, the situation is tricky because br_table doesn't
// support arguments. We have to split the critical edge.
let middle_block = dfg.blocks.add();
func.stencil.layout.append_block(middle_block);
let table = &mut dfg.jump_tables[*jt];
for block in table.iter_mut() {
for block in dfg.jump_tables[*jt].all_branches_mut() {
if *block == dest_block {
*block = middle_block;
}
}
if *destination == dest_block {
*destination = middle_block;
}
let mut cur = FuncCursor::new(func).at_bottom(middle_block);
let middle_jump_inst = cur.ins().jump(dest_block, &[val]);
Some((middle_block, middle_jump_inst))
@@ -1001,9 +992,6 @@ mod tests {
let block0 = func.dfg.make_block();
let block1 = func.dfg.make_block();
let block2 = func.dfg.make_block();
let mut jump_table = JumpTableData::new();
jump_table.push_entry(block2);
jump_table.push_entry(block1);
{
let mut cur = FuncCursor::new(&mut func);
cur.insert_block(block0);
@@ -1022,9 +1010,10 @@ mod tests {
ssa.def_var(x_var, x1, block0);
ssa.use_var(&mut func, x_var, I32, block0).0;
let br_table = {
let jump_table = JumpTableData::new(block2, vec![block2, block1]);
let jt = func.create_jump_table(jump_table);
let mut cur = FuncCursor::new(&mut func).at_bottom(block0);
cur.ins().br_table(x1, block2, jt)
cur.ins().br_table(x1, jt)
};
// block1