Commit bc073585 authored by Jason Ekstrand's avatar Jason Ekstrand
Browse files

nir/lower_variables: Use a real dominance DFS for variable renaming



Previously, we were just iterating over the program "in order" which
kind-of approximates a DFS, but not really.  In particular, we got the
following case wrong:

loop {
   a = 3;
   if (foo) {
      a = 5;
   } else {
      break;
   }
   use(a);
}

where use(a) would get 3 instead of 5 because of premature popping of the
SSA def stack.  Now, since we do an actaul DFS, we should evaluate use(a)
immediately after a = 5 and we should be ok.
Reviewed-by: default avatarConnor Abbott <cwabbott0@gmail.com>
parent dfb3abba
......@@ -725,10 +725,8 @@ add_phi_sources(nir_block *block, nir_block *pred,
}
static bool
lower_deref_to_ssa_block(nir_block *block, void *void_state)
rename_variables_block(nir_block *block, struct lower_variables_state *state)
{
struct lower_variables_state *state = void_state;
nir_foreach_instr_safe(block, instr) {
if (instr->type == nir_instr_type_phi) {
nir_phi_instr *phi = nir_instr_as_phi(instr);
......@@ -856,6 +854,9 @@ lower_deref_to_ssa_block(nir_block *block, void *void_state)
if (block->successors[1])
add_phi_sources(block->successors[1], block, state);
for (unsigned i = 0; i < block->num_dom_children; ++i)
rename_variables_block(block->dom_children[i], state);
return true;
}
......@@ -996,7 +997,7 @@ nir_lower_variables_impl(nir_function_impl *impl)
nir_metadata_require(impl, nir_metadata_dominance);
insert_phi_nodes(&state);
nir_foreach_block(impl, lower_deref_to_ssa_block, &state);
rename_variables_block(impl->start_block, &state);
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment