[Mesa-dev] [PATCH] i965/fs: Properly patch special values during VGRF compaction.

[Kenneth Graunke]

In addition to registers used by instructions, fs_visitor maintains
direct references to certain "special" values used for inputs/outputs.

When I added VGRF compaction, I overlooked these, believing that these
direct references weren't used once instructions were generated.  That
was wrong.  For example, pixel_x/y are used in virtual_grf_interferes(),
which is called by optimization passes and register allocation.

This patch treats all of them as used and patches them after compacting.
While it's not strictly necessary to patch all of them (as some aren't
used after emitting code), it seems safer to simply fix them all.

Fixes oglconform's textureswizzle/advanced.shader.targets, piglit's
glsl-fs-lots-of-tex, and glean's texCombine on pre-Gen6 hardware.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=56790
---
 src/mesa/drivers/dri/i965/brw_fs.cpp | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index dc2e5a6..fb772bc 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1130,6 +1130,27 @@ fs_visitor::compact_virtual_grfs()
       }
    }
 
+   /* In addition to registers used in instructions, fs_visitor keeps
+    * direct references to certain special values which must be patched:
+    */
+   fs_reg *special[] = {
+      &frag_depth, &pixel_x, &pixel_y, &pixel_w, &wpos_w, &dual_src_output,
+      &outputs[0], &outputs[1], &outputs[2], &outputs[3],
+      &outputs[4], &outputs[5], &outputs[6], &outputs[7],
+      &delta_x[0], &delta_x[1], &delta_x[2],
+      &delta_x[3], &delta_x[4], &delta_x[5],
+      &delta_y[0], &delta_y[1], &delta_y[2],
+      &delta_y[3], &delta_y[4], &delta_y[5],
+   };
+   STATIC_ASSERT(BRW_WM_BARYCENTRIC_INTERP_MODE_COUNT == 6);
+   STATIC_ASSERT(BRW_MAX_DRAW_BUFFERS == 8);
+
+   /* Treat all special values as used, to be conservative */
+   for (unsigned i = 0; i < ARRAY_SIZE(special); i++) {
+      if (special[i]->file == GRF)
+	 remap_table[special[i]->reg] = 0;
+   }
+
    /* Compact the GRF arrays. */
    int new_index = 0;
    for (int i = 0; i < this->virtual_grf_count; i++) {
@@ -1158,6 +1179,12 @@ fs_visitor::compact_virtual_grfs()
             inst->src[i].reg = remap_table[inst->src[i].reg];
       }
    }
+
+   /* Patch all the references to special values */
+   for (unsigned i = 0; i < ARRAY_SIZE(special); i++) {
+      if (special[i]->file == GRF && remap_table[special[i]->reg] != -1)
+	 special[i]->reg = remap_table[special[i]->reg];
+   }
 }
 
 bool
-- 
1.8.0