[Mesa-dev] [PATCH 2/2] i965: Make brw_reg_from_fs_reg() halve exec_size when compressed.

[Kenneth Graunke]

In a5d7e144eaf43fee37e6ff9e2de194407087632b, Connor generalized the
exec_size halving code to handle more cases.  As part of this, he made
it not halve anything if the region accessed falls completely in a
single register.

Unfortunately, it started producing some invalid regions:

-add(16)  g6<1>F  g10<8,8,1>UW    -g1<0,1,0>F    { align1 compr };
-add(16)  g8<1>F  g12<8,8,1>UW    -g1.1<0,1,0>F  { align1 compr };
+add(16)  g6<1>F  g10<16,16,1>UW  -g1<0,1,0>F    { align1 compr };
+add(16)  g8<1>F  g12<16,16,1>UW  -g1.1<0,1,0>F  { align1 compr };

Here, the UW source region completely fits within a register.  However,
we have to use instruction compression because the destination region
spans two registers.  <16,16,1> is invalid because it's compressed.

To handle this, skip the "everything fits in one register" case and
fall through to the exec_size halving case when compressed.

Fixes hundreds of Piglit regressions on GM965.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95370
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Cc: Connor Abbott <cwabbott0 at gmail.com>
Cc: Francisco Jerez <currojerez at riseup.net>
Cc: Matt Turner <mattst88 at gmail.com>
---
 src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index 4b85aaa..b9000d6 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -54,7 +54,8 @@ brw_file_from_reg(fs_reg *reg)
 }
 
 static struct brw_reg
-brw_reg_from_fs_reg(fs_inst *inst, fs_reg *reg, unsigned gen)
+brw_reg_from_fs_reg(const struct brw_codegen *p,
+                    fs_inst *inst, fs_reg *reg, unsigned gen)
 {
    struct brw_reg brw_reg;
 
@@ -65,7 +66,8 @@ 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 * reg->stride * type_sz(reg->type) <= 32) {
+      } else if (!p->compressed &&
+                 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,
@@ -1763,7 +1765,7 @@ fs_generator::generate_code(const cfg_t *cfg, int dispatch_width)
       }
 
       for (unsigned int i = 0; i < inst->sources; i++) {
-	 src[i] = brw_reg_from_fs_reg(inst, &inst->src[i], devinfo->gen);
+	 src[i] = brw_reg_from_fs_reg(p, inst, &inst->src[i], devinfo->gen);
 
 	 /* The accumulator result appears to get used for the
 	  * conditional modifier generation.  When negating a UD
@@ -1775,7 +1777,7 @@ fs_generator::generate_code(const cfg_t *cfg, int dispatch_width)
 		inst->src[i].type != BRW_REGISTER_TYPE_UD ||
 		!inst->src[i].negate);
       }
-      dst = brw_reg_from_fs_reg(inst, &inst->dst, devinfo->gen);
+      dst = brw_reg_from_fs_reg(p, inst, &inst->dst, devinfo->gen);
 
       brw_set_default_predicate_control(p, inst->predicate);
       brw_set_default_predicate_inverse(p, inst->predicate_inverse);
-- 
2.8.2