Mesa (master): meta/blit: Write depth only when asked for

[Topi Pohjolainen]

Module: Mesa
Branch: master
Commit: 97caf5fa04dbd2148378a9e83c0e232f51552ee2
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=97caf5fa04dbd2148378a9e83c0e232f51552ee2

Author: Topi Pohjolainen <topi.pohjolainen at intel.com>
Date:   Wed Jan 28 16:36:11 2015 +0200

meta/blit: Write depth only when asked for

Implementing an idea from Ken, on i965 the shader program for 2D
blits becomes significantly simpler.

Before:

pln(8)   g6<1>F    g4<0,1,0>F    g2<8,8,1>F  { align1 1Q compacted };
pln(8)   g7<1>F    g4.4<0,1,0>F  g2<8,8,1>F  { align1 1Q compacted };
send(8)  g2<1>UW   g6<8,8,1>F
         sampler (1, 0, 0, 1) mlen 2 rlen 4  { align1 1Q };
mov(8)   g123<1>F  g2<8,8,1>F                { align1 1Q compacted };
mov(8)   g124<1>F  g3<8,8,1>F                { align1 1Q compacted };
mov(8)   g125<1>F  g4<8,8,1>F                { align1 1Q compacted };
mov(8)   g126<1>F  g5<8,8,1>F                { align1 1Q compacted };
mov(8)   g127<1>F  g2<8,8,1>F                { align1 1Q compacted };
nop                                                             ;
sendc(8) null        g123<8,8,1>F
    render RT write SIMD8 LastRT Surface = 0 mlen 5 rlen 0 { align1 1Q EOT };

After:

pln(8)   g6<1>F     g4<0,1,0>F    g2<8,8,1>F   { align1 1Q compacted };
pln(8)   g7<1>F     g4.4<0,1,0>F  g2<8,8,1>F   { align1 1Q compacted };
send(8)  g124<1>UW  g6<8,8,1>F
         sampler (1, 0, 0, 1) mlen 2 rlen 4    { align1 1Q };
sendc(8) null        g124<8,8,1>F
   render RT write SIMD8 LastRT Surface = 0 mlen 4 rlen 0 { align1 1Q EOT };

v2 (Matt): Removed unintended white-space change

Signed-off-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Matt Turner <mattst88 at gmail.com>

---

 src/mesa/drivers/common/meta.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
index ec7564a..84d6337 100644
--- a/src/mesa/drivers/common/meta.c
+++ b/src/mesa/drivers/common/meta.c
@@ -293,10 +293,11 @@ _mesa_meta_setup_blit_shader(struct gl_context *ctx,
                 "void main()\n"
                 "{\n"
                 "   gl_FragColor = %s(texSampler, %s);\n"
-                "   gl_FragDepth = gl_FragColor.x;\n"
+                "%s"
                 "}\n",
                 fs_preprocess, shader->type, fs_input,
-                shader->func, shader->texcoords);
+                shader->func, shader->texcoords,
+                do_depth ?  "   gl_FragDepth = gl_FragColor.x;\n" : "");
 
    _mesa_meta_compile_and_link_program(ctx, vs_source, fs_source,
                                        ralloc_asprintf(mem_ctx, "%s blit",