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@anholt.net>

1 files 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;
+         }
       }
    }