From: Francisco Jerez <currojerez@riseup.net>
Date: Fri, 2 Sep 2016 05:08:29 +0000 (-0700)
Subject: i965/vec4: Don't coalesce registers with overlapping writes not matching the MOV... 
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=3a74e437fdec02c28749c94bc1bcf21c3c4b48d7;p=mesa.git

i965/vec4: Don't coalesce registers with overlapping writes not matching the MOV source.

In preparation for adding support for sub-GRF offsets to the VEC4 IR.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
---

diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index d9dbc4c8543..8f8d2623416 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1181,8 +1181,11 @@ vec4_visitor::opt_register_coalesce()
                break;
             }
 
-            /* This doesn't handle coalescing of multiple registers. */
-            if (scan_inst->size_written > REG_SIZE)
+            /* This only handles coalescing of a single register starting at
+             * the source offset of the copy instruction.
+             */
+            if (scan_inst->size_written > REG_SIZE ||
+                scan_inst->dst.offset != inst->src[0].offset)
                break;
 
 	    /* Mark which channels we found unconditional writes for. */
@@ -1246,8 +1249,7 @@ vec4_visitor::opt_register_coalesce()
 	 while (scan_inst != inst) {
 	    if (scan_inst->dst.file == VGRF &&
                 scan_inst->dst.nr == inst->src[0].nr &&
-		scan_inst->dst.offset / REG_SIZE ==
-                 inst->src[0].offset / REG_SIZE) {
+		scan_inst->dst.offset == inst->src[0].offset) {
                scan_inst->reswizzle(inst->dst.writemask,
                                     inst->src[0].swizzle);
 	       scan_inst->dst.file = inst->dst.file;