nir: allow nir_lower_phis_to_scalar() on more src types

[mesa.git] / src / compiler / nir / nir_lower_phis_to_scalar.c

diff --git a/src/compiler/nir/nir_lower_phis_to_scalar.c b/src/compiler/nir/nir_lower_phis_to_scalar.c
index 16001f736852087e79acaa3ef54dcdfef1c2dd61..c58a67826cee614a62c64518e034ffed0e8bf82a 100644 (file)
--- a/src/compiler/nir/nir_lower_phis_to_scalar.c
+++ b/src/compiler/nir/nir_lower_phis_to_scalar.c
@@ -75,10 +75,15 @@ is_phi_src_scalarizable(nir_phi_src *src,
       return should_lower_phi(nir_instr_as_phi(src_instr), state);
 
    case nir_instr_type_load_const:
-   case nir_instr_type_ssa_undef:
       /* These are trivially scalarizable */
       return true;
 
+   case nir_instr_type_ssa_undef:
+      /* The caller of this function is going to OR the results and we don't
+       * want undefs to count so we return false.
+       */
+      return false;
+
    case nir_instr_type_intrinsic: {
       nir_intrinsic_instr *src_intrin = nir_instr_as_intrinsic(src_instr);
 
@@ -150,11 +155,16 @@ should_lower_phi(nir_phi_instr *phi, struct lower_phis_to_scalar_state *state)
     */
    entry = _mesa_hash_table_insert(state->phi_table, phi, (void *)(intptr_t)1);
 
-   bool scalarizable = true;
+   bool scalarizable = false;
 
    nir_foreach_phi_src(src, phi) {
+      /* This loop ignores srcs that are not scalarizable because its likely
+       * still worth copying to temps if another phi source is scalarizable.
+       * This reduces register spilling by a huge amount in the i965 driver for
+       * Deus Ex: MD.
+       */
       scalarizable = is_phi_src_scalarizable(src, state);
-      if (!scalarizable)
+      if (scalarizable)
          break;
    }