nir: Do opt_algebraic in reverse order.

Walking the SSA definitions in order means that we consider the smallest
algebraic optimizations before larger optimizations. So if a smaller
rule is part of a larger rule, the smaller one will happen first,
preventing the larger one from happening.

instructions in affected programs: 32721 -> 32611 (-0.34%)
helped: 106

In programs whose nir_optimize loop count changes (129 of them):

   before:  1164 optimization loops
   after:   1071 optimization loops

Of the 129 affected, 16 programs' optimization loop counts increased.

Prevents regressions and annoyances in the next commits.

Reviewed-by: Eduardo Lima Mitev <elima@igalia.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>

diff --git a/src/compiler/nir/nir_algebraic.py b/src/compiler/nir/nir_algebraic.py
index a30652f..77ad35e 100644 (file)
--- a/src/compiler/nir/nir_algebraic.py
+++ b/src/compiler/nir/nir_algebraic.py
@@ -216,7 +216,7 @@ ${pass_name}_block(nir_block *block, void *void_state)
 {
    struct opt_state *state = void_state;
 
-   nir_foreach_instr_safe(block, instr) {
+   nir_foreach_instr_reverse_safe(block, instr) {
       if (instr->type != nir_instr_type_alu)
          continue;
 
@@ -255,7 +255,7 @@ ${pass_name}_impl(nir_function_impl *impl, const bool *condition_flags)
    state.progress = false;
    state.condition_flags = condition_flags;
 
-   nir_foreach_block(impl, ${pass_name}_block, &state);
+   nir_foreach_block_reverse(impl, ${pass_name}_block, &state);
 
    if (state.progress)
       nir_metadata_preserve(impl, nir_metadata_block_index |