When using MRT on Gen4-5, we have to simulate GL's alpha test feature
by emitting discards in the fragment shader. In this case, it makes
sense to set prog_data->uses_kill, which means the fragment shader may
kill pixels via the discard mechanism.
This saves us from having to look an extra key value in a couple of
places, including in the generator.
Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
---
src/mesa/drivers/dri/i965/brw_fs.cpp | 2 +-
src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 2 +-
src/mesa/drivers/dri/i965/brw_wm.c | 5 ++++-
3 files changed, 6 insertions(+), 3 deletions(-)
This series was tested on 965, G45, Ironlake, Sandybridge, Ivybridge,
Baytrail, and Haswell. 965 had a few random changes that looked totally
unrelated, but everything else worked fine. Not tested on Broadwell.
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 0ffb07f..fdd1bb3 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -3601,7 +3601,7 @@ fs_visitor::run()
bool alpha_test_func =
(stage == MESA_SHADER_FRAGMENT) &&
((brw_wm_prog_key*) this->key)->alpha_test_func;
- if (uses_kill || alpha_test_func) {
+ if (uses_kill) {
fs_inst *discard_init = emit(FS_OPCODE_MOV_DISPATCH_TO_FLAGS);
discard_init->flag_subreg = 1;
}
diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index f61e7a1..67dfe81 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -179,7 +179,7 @@ fs_generator::generate_fb_write(fs_inst *inst, struct
brw_reg payload)
/* On HSW, the GPU will use the predicate on SENDC, unless the header is
* present.
*/
- if (prog_data->uses_kill || key->alpha_test_func) {
+ if (prog_data->uses_kill) {
struct brw_reg pixel_mask;
if (brw->gen >= 6)
diff --git a/src/mesa/drivers/dri/i965/brw_wm.c
b/src/mesa/drivers/dri/i965/brw_wm.c
index 5863573..34500e2 100644
--- a/src/mesa/drivers/dri/i965/brw_wm.c
+++ b/src/mesa/drivers/dri/i965/brw_wm.c
@@ -156,7 +156,10 @@ bool do_wm_prog(struct brw_context *brw,
fs = prog->_LinkedShaders[MESA_SHADER_FRAGMENT];
memset(&prog_data, 0, sizeof(prog_data));
- prog_data.uses_kill = fp->program.UsesKill;
+ /* 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;
/* Allocate the references to the uniforms that will end up in the
* prog_data associated with the compiled program, and which will be freed
--
2.1.3
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