Mesa (master): nir/search: Save/ restore the variables_seen bitmask when matching

[Jason Ekstrand]

Module: Mesa
Branch: master
Commit: fb5f411248d9c342ed249228f7dac713dcfd3d06
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=fb5f411248d9c342ed249228f7dac713dcfd3d06

Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Fri May  8 09:48:33 2015 -0700

nir/search: Save/restore the variables_seen bitmask when matching

Shader-db results on Broadwell:

   total instructions in shared programs: 7152330 -> 7137006 (-0.21%)
   instructions in affected programs:     1330548 -> 1315224 (-1.15%)
   helped:                                5797
   HURT:                                  76
   GAINED:                                0
   LOST:                                  8

Reviewed-by: Connor Abbott <cwabbott0 at gmail.com>

---

 src/glsl/nir/nir_search.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/glsl/nir/nir_search.c b/src/glsl/nir/nir_search.c
index 1c171f2..0c4e48c 100644
--- a/src/glsl/nir/nir_search.c
+++ b/src/glsl/nir/nir_search.c
@@ -207,6 +207,11 @@ match_expression(const nir_search_expression *expr, nir_alu_instr *instr,
       }
    }
 
+   /* Stash off the current variables_seen bitmask.  This way we can
+    * restore it prior to matching in the commutative case below.
+    */
+   unsigned variables_seen_stash = state->variables_seen;
+
    bool matched = true;
    for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
       if (!match_value(expr->srcs[i], instr, i, num_components,
@@ -221,6 +226,13 @@ match_expression(const nir_search_expression *expr, nir_alu_instr *instr,
 
    if (nir_op_infos[instr->op].algebraic_properties & NIR_OP_IS_COMMUTATIVE) {
       assert(nir_op_infos[instr->op].num_inputs == 2);
+
+      /* Restore the variables_seen bitmask.  If we don't do this, then we
+       * could end up with an erroneous failure due to variables found in the
+       * first match attempt above not matching those in the second.
+       */
+      state->variables_seen = variables_seen_stash;
+
       if (!match_value(expr->srcs[0], instr, 1, num_components,
                        swizzle, state))
          return false;