Mesa (master): i965/fs: Check for interference after finding all channels.

[Matt Turner]

Module: Mesa
Branch: master
Commit: 99437b730f53dfa5d74f601415d8e2b66b68a3fd
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=99437b730f53dfa5d74f601415d8e2b66b68a3fd

Author: Matt Turner <mattst88 at gmail.com>
Date:   Thu Mar 27 10:15:19 2014 -0700

i965/fs: Check for interference after finding all channels.

It's more likely that we won't find writes to all channels than one will
interfere, and calculating interference is more expensive. This change
will also help prepare for coalescing load_payload instructions'
operands.

Also update the live intervals for all channels, and not just the last
that we saw.

Reviewed-by: Eric Anholt <eric at anholt.net>

---

 .../drivers/dri/i965/brw_fs_register_coalesce.cpp  |   37 ++++++++++++++------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
index 5c16798..c71fd47 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
@@ -122,6 +122,8 @@ fs_visitor::register_coalesce()
    int reg_from = -1, reg_to = -1;
    int reg_to_offset[MAX_SAMPLER_MESSAGE_SIZE];
    fs_inst *mov[MAX_SAMPLER_MESSAGE_SIZE];
+   int var_to[MAX_SAMPLER_MESSAGE_SIZE];
+   int var_from[MAX_SAMPLER_MESSAGE_SIZE];
 
    foreach_list(node, &this->instructions) {
       fs_inst *inst = (fs_inst *)node;
@@ -129,12 +131,6 @@ fs_visitor::register_coalesce()
       if (!is_coalesce_candidate(inst, virtual_grf_sizes))
          continue;
 
-      int var_from = live_intervals->var_from_reg(&inst->src[0]);
-      int var_to = live_intervals->var_from_reg(&inst->dst);
-
-      if (!can_coalesce_vars(live_intervals, &instructions, inst, var_to, var_from))
-         continue;
-
       if (reg_from != inst->src[0].reg) {
          reg_from = inst->src[0].reg;
 
@@ -158,6 +154,21 @@ fs_visitor::register_coalesce()
       if (channels_remaining)
          continue;
 
+      bool can_coalesce = true;
+      for (int i = 0; i < src_size; i++) {
+         var_to[i] = live_intervals->var_from_vgrf[reg_to] + reg_to_offset[i];
+         var_from[i] = live_intervals->var_from_vgrf[reg_from] + i;
+
+         if (!can_coalesce_vars(live_intervals, &instructions, inst,
+                                var_to[i], var_from[i])) {
+            can_coalesce = false;
+            break;
+         }
+      }
+
+      if (!can_coalesce)
+         continue;
+
       bool removed = false;
       for (int i = 0; i < src_size; i++) {
          if (mov[i]) {
@@ -196,11 +207,15 @@ fs_visitor::register_coalesce()
       }
 
       if (removed) {
-         live_intervals->start[var_to] = MIN2(live_intervals->start[var_to],
-                                              live_intervals->start[var_from]);
-         live_intervals->end[var_to] = MAX2(live_intervals->end[var_to],
-                                            live_intervals->end[var_from]);
-         reg_from = -1;
+         for (int i = 0; i < src_size; i++) {
+            live_intervals->start[var_to[i]] =
+               MIN2(live_intervals->start[var_to[i]],
+                    live_intervals->start[var_from[i]]);
+            live_intervals->end[var_to[i]] =
+               MAX2(live_intervals->end[var_to[i]],
+                    live_intervals->end[var_from[i]]);
+            reg_from = -1;
+         }
       }
    }