[Mesa-dev] [PATCH] i965/fs: Clarify and optimize register coalescing interference check.

[Matt Turner]

With bblock_t::end_ip, we can skip entire blocks rather than checking
every instruction in them. Also by making the loops nested (explicitly,
it already was a nested loop), the continue seen at the end of the first
hunk (when viewed with git show -w) will do what the programmer expects.

No functional change.
---
 .../drivers/dri/i965/brw_fs_register_coalesce.cpp  | 28 +++++++++++-----------
 1 file changed, 14 insertions(+), 14 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 62788cd..9c8ca32 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
@@ -126,26 +126,26 @@ can_coalesce_vars(brw::fs_live_variables *live_intervals,
       return false;
 
    int start_ip = MIN2(start_to, start_from);
-   int scan_ip = -1;
 
-   foreach_block_and_inst(block, fs_inst, scan_inst, cfg) {
-      scan_ip++;
-
-      if (scan_ip < start_ip)
+   foreach_block(block, cfg) {
+      if (start_ip > block->end_ip)
          continue;
 
-      if (scan_inst->is_control_flow())
-         return false;
+      int scan_ip = block->start_ip - 1;
 
-      if (scan_ip <= live_intervals->start[var_to])
-         continue;
+      foreach_inst_in_block(fs_inst, scan_inst, block) {
+         scan_ip++;
+
+         if (scan_ip <= live_intervals->start[var_to])
+            continue;
 
-      if (scan_ip > live_intervals->end[var_to])
-         return true;
+         if (scan_ip > live_intervals->end[var_to])
+            return true;
 
-      if (scan_inst->dst.equals(inst->dst) ||
-          scan_inst->dst.equals(inst->src[0]))
-         return false;
+         if (scan_inst->dst.equals(inst->dst) ||
+             scan_inst->dst.equals(inst->src[0]))
+            return false;
+      }
    }
 
    return true;
-- 
2.0.4