Mesa (master): i965/vec4: Perform CSE on CMP(N) instructions.

[Matt Turner]

Module: Mesa
Branch: master
Commit: 6f7c4a8d05df0337a992ff485c9de86f8bf81e0a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=6f7c4a8d05df0337a992ff485c9de86f8bf81e0a

Author: Matt Turner <mattst88 at gmail.com>
Date:   Wed Jun 11 13:49:34 2014 -0700

i965/vec4: Perform CSE on CMP(N) instructions.

Port of commit b16b3c87 to the vec4 code.

No shader-db improvements, but might as well. The fs backend saw an
improvement because it's scalar and multiple identical CMP instructions
were generated by the SEL peepholes.

---

 src/mesa/drivers/dri/i965/brw_vec4_cse.cpp |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp b/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
index f3a69ed..eeaa743 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
@@ -56,6 +56,8 @@ is_expression(const vec4_instruction *const inst)
    case BRW_OPCODE_SHR:
    case BRW_OPCODE_SHL:
    case BRW_OPCODE_ASR:
+   case BRW_OPCODE_CMP:
+   case BRW_OPCODE_CMPN:
    case BRW_OPCODE_ADD:
    case BRW_OPCODE_MUL:
    case BRW_OPCODE_FRC:
@@ -135,7 +137,7 @@ vec4_visitor::opt_cse_local(bblock_t *block, exec_list *aeb)
 
       /* Skip some cases. */
       if (is_expression(inst) && !inst->predicate && inst->mlen == 0 &&
-          !inst->conditional_mod)
+          (inst->dst.file != HW_REG || inst->dst.is_null()))
       {
          bool found = false;
 
@@ -195,6 +197,19 @@ vec4_visitor::opt_cse_local(bblock_t *block, exec_list *aeb)
       }
 
       foreach_in_list_safe(aeb_entry, entry, aeb) {
+         /* Kill all AEB entries that write a different value to or read from
+          * the flag register if we just wrote it.
+          */
+         if (inst->writes_flag()) {
+            if (entry->generator->reads_flag() ||
+                (entry->generator->writes_flag() &&
+                 !instructions_match(inst, entry->generator))) {
+               entry->remove();
+               ralloc_free(entry);
+               continue;
+            }
+         }
+
          for (int i = 0; i < 3; i++) {
             src_reg *src = &entry->generator->src[i];