[Mesa-dev] [PATCH 38/59] i965/fs: extend exec_size halving in the generator

[Samuel Iglesias Gonsálvez]

From: Connor Abbott <connor.w.abbott at intel.com>

The HW has a restriction that only vertical stride may cross register
boundaries. Previously, this only mattered for SIMD16 instructions where
we needed to use the same regioning parameters as the equivalent SIMD8
instruction but double the exec size. But we need to do the same
splitting for 64-bit instructions as well as instructions with a stride
of 2 (which effectively consume 64 bits per element). Fix up the code to
do the right thing instead of special-casing SIMD16.
---
 src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index 8654ca4..0743e74 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -65,8 +65,9 @@ brw_reg_from_fs_reg(fs_inst *inst, fs_reg *reg, unsigned gen)
    case VGRF:
       if (reg->stride == 0) {
          brw_reg = brw_vec1_reg(brw_file_from_reg(reg), reg->nr, 0);
-      } else if (inst->exec_size < 8) {
-         brw_reg = brw_vec8_reg(brw_file_from_reg(reg), reg->nr, 0);
+      } else if (inst->exec_size * reg->stride * type_sz(reg->type) <= 32) {
+         brw_reg = brw_vecn_reg(inst->exec_size, brw_file_from_reg(reg),
+                                reg->nr, 0);
          brw_reg = stride(brw_reg, inst->exec_size * reg->stride,
                           inst->exec_size, reg->stride);
       } else {
@@ -76,11 +77,14 @@ brw_reg_from_fs_reg(fs_inst *inst, fs_reg *reg, unsigned gen)
           * rule implies that elements within a 'Width' cannot cross GRF
           * boundaries.
           *
-          * So, for registers with width > 8, we have to use a width of 8
-          * and trust the compression state to sort out the exec size.
+          * So, for registers that are large enough, we have to split the exec
+          * size in two and trust the compression state to sort it out.
           */
-         brw_reg = brw_vec8_reg(brw_file_from_reg(reg), reg->nr, 0);
-         brw_reg = stride(brw_reg, 8 * reg->stride, 8, reg->stride);
+         assert(inst->exec_size / 2 * reg->stride * type_sz(reg->type) <= 32);
+         brw_reg = brw_vecn_reg(inst->exec_size / 2, brw_file_from_reg(reg),
+                                reg->nr, 0);
+         brw_reg = stride(brw_reg, inst->exec_size / 2 * reg->stride,
+                          inst->exec_size / 2, reg->stride);
       }
 
       brw_reg = retype(brw_reg, reg->type);
-- 
2.5.0