[Mesa-dev] [PATCH 88/95] i965/vec4: split instructions that read 64-bit attrs in TessEval

[Iago Toral Quiroga]

The tessellation evaluation stage generates source regions with a vstride=0
for these so they hit the gen7 hardware decompression bug. Split them to
prevent this.
---
 src/mesa/drivers/dri/i965/brw_vec4.cpp | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index 9b5d048..7ea94cd 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -2029,6 +2029,7 @@ vec4_visitor::convert_to_hw_regs()
  */
 static unsigned
 get_lowered_simd_width(const struct brw_device_info *devinfo,
+                       unsigned stage,
                        const vec4_instruction *inst)
 {
    /* For now we only need to split some cases of double-precision instructions
@@ -2064,8 +2065,17 @@ get_lowered_simd_width(const struct brw_device_info *devinfo,
    for (unsigned i = 0; i < 3; i++) {
       if (inst->src[i].file == BAD_FILE)
          continue;
+
       if (inst->regs_read(i) < 2)
          lowered_width = MIN2(lowered_width, 4);
+
+      /* The tessellation evaluation stage generates code with source regions
+       * that use a vstride 0 for all attributes, which makes them hit
+       * the associated instruction decompression bug in gen7. Split them
+       * to prevent this.
+       */
+      if (stage == MESA_SHADER_TESS_EVAL && inst->src[i].file == ATTR)
+         lowered_width = MIN2(lowered_width, 4);
    }
 
    return lowered_width;
@@ -2077,7 +2087,8 @@ vec4_visitor::lower_simd_width()
    bool progress = false;
 
    foreach_block_and_inst_safe(block, vec4_instruction, inst, cfg) {
-      const unsigned lowered_width = get_lowered_simd_width(devinfo, inst);
+      const unsigned lowered_width =
+         get_lowered_simd_width(devinfo, stage, inst);
       assert(lowered_width <= inst->exec_size);
       if (lowered_width == inst->exec_size)
          continue;
-- 
2.7.4