i965/fs: Simplify instruction rewrite loop in the register coalesce pass.

For some reason the loop that rewrites all occurrences of the
coalesced register was iterating over all possible offsets until it
would find one that compares equal to the offset of a source or
destination of any instruction in the program.  Since the mapping
between old and new offsets is already available in the regs_to_offset
array and we know that the whole register has been coalesced we can
just look it up.

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>

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 20a548000996cf4193266a39fc20d40fe2de4cbd..72e873857ced950272a885b15db2914b50ba3e2c 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
@@ -241,20 +241,19 @@ fs_visitor::register_coalesce()
       }
 
       foreach_block_and_inst(block, fs_inst, scan_inst, cfg) {
-         for (int i = 0; i < src_size; i++) {
-            if (scan_inst->dst.file == GRF &&
-                scan_inst->dst.reg == reg_from &&
-                scan_inst->dst.reg_offset == i) {
-               scan_inst->dst.reg = reg_to;
-               scan_inst->dst.reg_offset = reg_to_offset[i];
-            }
-            for (int j = 0; j < scan_inst->sources; j++) {
-               if (scan_inst->src[j].file == GRF &&
-                   scan_inst->src[j].reg == reg_from &&
-                   scan_inst->src[j].reg_offset == i) {
-                  scan_inst->src[j].reg = reg_to;
-                  scan_inst->src[j].reg_offset = reg_to_offset[i];
-               }
+         if (scan_inst->dst.file == GRF &&
+             scan_inst->dst.reg == reg_from) {
+            scan_inst->dst.reg = reg_to;
+            scan_inst->dst.reg_offset =
+               reg_to_offset[scan_inst->dst.reg_offset];
+         }
+
+         for (int j = 0; j < scan_inst->sources; j++) {
+            if (scan_inst->src[j].file == GRF &&
+                scan_inst->src[j].reg == reg_from) {
+               scan_inst->src[j].reg = reg_to;
+               scan_inst->src[j].reg_offset =
+                  reg_to_offset[scan_inst->src[j].reg_offset];
             }
          }
       }