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>

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 5c16798d68bc139158bd41a94413dc850608da5f..c71fd47bbe7b497a6445606271992c6b28977644 100644 (file)
--- 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;
+         }
       }
    }