[Mesa-dev] [PATCH] Revert "nir: Make nir_opt_remove_phis see through moves."

[Kenneth Graunke]

This reverts commit 144cbf89879103c45f79b7c5b923ebad63f08c55.

It doesn't work.  Given a phi after if/else blocks where both phi
sources are identical MOVs, it rewrites the phi destination to use
the first def it encounters...namely the result of the mov in the
then block.  This results in the else branch's value being thrown
out entirely, which is quite bogus.

Fixes 12 CTS tests:
ES31-CTS.functional.tessellation.invariance.outer_edge_symmetry.quads*

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/compiler/nir/nir_opt_remove_phis.c | 24 +-----------------------
 1 file changed, 1 insertion(+), 23 deletions(-)

diff --git a/src/compiler/nir/nir_opt_remove_phis.c b/src/compiler/nir/nir_opt_remove_phis.c
index ee92fbe..f1e7bb0 100644
--- a/src/compiler/nir/nir_opt_remove_phis.c
+++ b/src/compiler/nir/nir_opt_remove_phis.c
@@ -27,26 +27,6 @@
 
 #include "nir.h"
 
-static nir_alu_instr *
-get_parent_mov(nir_ssa_def *ssa)
-{
-   if (ssa->parent_instr->type != nir_instr_type_alu)
-      return NULL;
-
-   nir_alu_instr *alu = nir_instr_as_alu(ssa->parent_instr);
-   return (alu->op == nir_op_imov || alu->op == nir_op_fmov) ? alu : NULL;
-}
-
-static bool
-matching_mov(nir_alu_instr *mov1, nir_ssa_def *ssa)
-{
-   if (!mov1)
-      return false;
-
-   nir_alu_instr *mov2 = get_parent_mov(ssa);
-   return mov2 && nir_alu_srcs_equal(mov1, mov2, 0, 0);
-}
-
 /*
  * This is a pass for removing phi nodes that look like:
  * a = phi(b, b, b, ...)
@@ -74,7 +54,6 @@ remove_phis_block(nir_block *block)
       nir_phi_instr *phi = nir_instr_as_phi(instr);
 
       nir_ssa_def *def = NULL;
-      nir_alu_instr *mov = NULL;
       bool srcs_same = true;
 
       nir_foreach_phi_src(src, phi) {
@@ -96,9 +75,8 @@ remove_phis_block(nir_block *block)
          
          if (def == NULL) {
             def  = src->src.ssa;
-            mov = get_parent_mov(def);
          } else {
-            if (src->src.ssa != def && !matching_mov(mov, src->src.ssa)) {
+            if (src->src.ssa != def) {
                srcs_same = false;
                break;
             }
-- 
2.9.3