i965/fs: Remove broken optimization for live intervals in loops.

The theory here was to detect a temporary variable used within a loop,
and avoid considering it live across the entire loop.  However, it was
overeager and failed when the first definition of the variable
appeared within the loop but was only conditionally defined.

Fixes glsl-fs-loop-redundant-condition.

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index cada140..99cd8f8 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -2812,8 +2812,7 @@ fs_visitor::calculate_live_intervals()
            if (inst->src[i].file == GRF && inst->src[i].reg != 0) {
               int reg = inst->src[i].reg;
 
-              if (!loop_depth || (this->virtual_grf_sizes[reg] == 1 &&
-                                  def[reg] >= bb_header_ip)) {
+              if (!loop_depth) {
                  use[reg] = ip;
               } else {
                  def[reg] = MIN2(loop_start, def[reg]);
@@ -2829,8 +2828,7 @@ fs_visitor::calculate_live_intervals()
         if (inst->dst.file == GRF && inst->dst.reg != 0) {
            int reg = inst->dst.reg;
 
-           if (!loop_depth || (this->virtual_grf_sizes[reg] == 1 &&
-                               !inst->predicated)) {
+           if (!loop_depth) {
               def[reg] = MIN2(def[reg], ip);
            } else {
               def[reg] = MIN2(def[reg], loop_start);