i965/fs: Don't set flag_subreg_nr = 1 on predicated FB write setup.

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 <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>

diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index d3509a0f1dedfa06c9dfa4b954e0c224f7153510..208b54f7fddc1a0370fdabeb68b2b67879efb867 100644 (file)
--- 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.