Mesa (master): i965/fs: Only emit FS_OPCODE_PLACEHOLDER_HALT if there are discards
Ben Widawsky
bwidawsk at kemper.freedesktop.org
Tue Apr 14 22:23:01 UTC 2015
Module: Mesa
Branch: master
Commit: 6866378cf42c86d03f38616804e6714a932ab70b
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=6866378cf42c86d03f38616804e6714a932ab70b
Author: Ben Widawsky <benjamin.widawsky at intel.com>
Date: Fri Apr 10 10:04:55 2015 -0700
i965/fs: Only emit FS_OPCODE_PLACEHOLDER_HALT if there are discards
Based originally on a patch from Ken in May 2014 of the same title. Things
changed enough that I didn't feel comfortable leaving his authorship.
v2: Replace fp->UsesKill with wm_prog_data->uses_kill. Since Ken took the time
to also explain the difference to me, here is his explanation for posterity:
"fp->UsesKill indicates that a ARB_fragment_program shader uses the KIL
instruction, or that a GLSL shader uses the "discard" insntruction
(which are analogous).
On Gen4-5, we sometimes have to simulate OpenGL's "Alpha Test" feature
by emitting shader code that implicitly does a "discard" instruction.
In the key setup, we do:
/* key->alpha_test_func means simulating alpha testing via discards,
* so the shader definitely kills pixels.
*/
prog_data.uses_kill = fp->program.UsesKill || key->alpha_test_func;
Even though the shader may not technically contain a "discard", we need
to act as if it does.
I've also been trying to move the i965 state setup code to use
brw_wm_prog_key for everything, rather than poking at core Mesa's
gl_program/gl_fragment_program/gl_shader/gl_shader_program structures.
--Ken"
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
Reviewed-by: Matt Turner <mattst88 at gmail.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
---
src/mesa/drivers/dri/i965/brw_fs.cpp | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index aea1ebb..f04fb59 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1699,6 +1699,8 @@ fs_visitor::emit_math(enum opcode opcode, fs_reg dst, fs_reg src0, fs_reg src1)
void
fs_visitor::emit_discard_jump()
{
+ assert(((brw_wm_prog_data*) this->prog_data)->uses_kill);
+
/* For performance, after a discard, jump to the end of the
* shader if all relevant channels have been discarded.
*/
@@ -3958,7 +3960,8 @@ fs_visitor::run_fs()
if (failed)
return false;
- emit(FS_OPCODE_PLACEHOLDER_HALT);
+ if (wm_prog_data->uses_kill)
+ emit(FS_OPCODE_PLACEHOLDER_HALT);
if (wm_key->alpha_test_func)
emit_alpha_test();
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