mesa: add/update comments in _mesa_copy_buffer_subdata()

[mesa.git] / src / mesa / drivers / dri / i965 / brw_vec4_copy_propagation.cpp

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
index 95aa30614b155c8c239e3031b6055b9ec2091273..4d27c53ddf390f8cbdb48bc1991b1eb2f0044f5a 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
@@ -297,30 +297,27 @@ vec4_visitor::opt_copy_propagation()
       }
 
       /* Track available source registers. */
-      if (is_direct_copy(inst)) {
-        int reg = virtual_grf_reg_map[inst->dst.reg] + inst->dst.reg_offset;
+      if (inst->dst.file == GRF) {
+        const int reg =
+           virtual_grf_reg_map[inst->dst.reg] + inst->dst.reg_offset;
+
+        /* Update our destination's current channel values.  For a direct copy,
+         * the value is the newly propagated source.  Otherwise, we don't know
+         * the new value, so clear it.
+         */
+        bool direct_copy = is_direct_copy(inst);
         for (int i = 0; i < 4; i++) {
            if (inst->dst.writemask & (1 << i)) {
-              cur_value[reg][i] = &inst->src[0];
+              cur_value[reg][i] = direct_copy ? &inst->src[0] : NULL;
            }
         }
-        continue;
-      }
 
-      /* For any updated channels, clear tracking of them as a source
-       * or destination.
-       */
-      if (inst->dst.file == GRF) {
+        /* Clear the records for any registers whose current value came from
+         * our destination's updated channels, as the two are no longer equal.
+         */
         if (inst->dst.reladdr)
            memset(cur_value, 0, sizeof(cur_value));
         else {
-           int reg = virtual_grf_reg_map[inst->dst.reg] + inst->dst.reg_offset;
-
-           for (int i = 0; i < 4; i++) {
-              if (inst->dst.writemask & (1 << i))
-                 cur_value[reg][i] = NULL;
-           }
-
            for (int i = 0; i < virtual_grf_reg_count; i++) {
               for (int j = 0; j < 4; j++) {
                  if (inst->dst.writemask & (1 << j) &&