On Haswell, we implement "discard" via predicated SEND messages, using
f0.1 instead of f0.0. To accomplish this, we set inst->flag_subreg to 1
on the FS_OPCODE_FB_WRITE.
Most instructions using fs_inst::flag_subreg expand to a single assembly
instruction. However, FS_OPCODE_FB_WRITE can generate several MOVs for
setting up header information. We don't want to set flag_subreg on
those, so override the default state back to 0.
Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
Reviewed-by: Matt Turner <matts...@gmail.com>
---
src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index d3509a0..208b54f 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -154,6 +154,7 @@ fs_generator::generate_fb_write(fs_inst *inst)
brw_set_default_mask_control(p, BRW_MASK_DISABLE);
brw_set_default_predicate_control(p, BRW_PREDICATE_NONE);
brw_set_default_compression_control(p, BRW_COMPRESSION_NONE);
+ brw_set_default_flag_reg(p, 0, 0);
/* On HSW, the GPU will use the predicate on SENDC, unless the header is
* present.
--
2.0.2
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