gallium: add a a new cap for changing the TGSI TG4 instruction encoding

Accessing the TG4 component via immediates in the llvmpipe backend is quite
messy (like really messy). Roland suggested we change the instruction encoding,
so introduce a cap to allow the component to be selected to be store in the
sampler swizzle, which should be otherwise unused.

I could probably switch all drivers over, but virgl would need some work that
I'd prefer not to rush it.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>

diff --git a/src/gallium/auxiliary/util/u_screen.c b/src/gallium/auxiliary/util/u_screen.c
index ba99ec0615dad5f5998b406dcedbae4f012cf64a..bf5b9daad7ed4daf37eae515724daeeed3d63ec8 100644 (file)
--- a/src/gallium/auxiliary/util/u_screen.c
+++ b/src/gallium/auxiliary/util/u_screen.c
@@ -341,6 +341,7 @@ u_pipe_screen_get_param_defaults(struct pipe_screen *pscreen,
    case PIPE_CAP_ATOMIC_FLOAT_MINMAX:
    case PIPE_CAP_SHADER_SAMPLES_IDENTICAL:
    case PIPE_CAP_TGSI_ATOMINC_WRAP:
+   case PIPE_CAP_TGSI_TG4_COMPONENT_IN_SWIZZLE:
       return 0;
 
    case PIPE_CAP_MAX_GS_INVOCATIONS:

diff --git a/src/gallium/docs/source/screen.rst b/src/gallium/docs/source/screen.rst
index 9acab6fafc5bc69f104167fd29dacfbfe2a32492..1c402b033919c93e1c4204078cc62d90dc70c269 100644 (file)
--- a/src/gallium/docs/source/screen.rst
+++ b/src/gallium/docs/source/screen.rst
@@ -558,6 +558,7 @@ The integer capabilities:
 * ``PIPE_CAP_GL_SPIRV``: True if the driver supports ARB_gl_spirv extension.
 * ``PIPE_CAP_GL_SPIRV_VARIABLE_POINTERS``: True if the driver supports Variable Pointers in SPIR-V shaders.
 * ``PIPE_CAP_DEMOTE_TO_HELPER_INVOCATION``: True if driver supports demote keyword in GLSL programs.
+* ``PIPE_CAP_TGSI_TG4_COMPONENT_IN_SWIZZLE``: True if driver wants the TG4 component encoded in sampler swizzle rather than as a separate source.
 
 .. _pipe_capf:
 

diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index d58b23f024b3998d11476b49d03c8175670bac8b..e053e821ecd54abfea2c7f1d4a14e5dbe01870a2 100644 (file)
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -962,14 +962,22 @@ XXX doesn't look like most of the opcodes really belong here.
   require another CAP is hw can do it natively. For now we lower that before
   TGSI.
 
+  PIPE_CAP_TGSI_TG4_COMPONENT_IN_SWIZZLE changes the encoding so that component
+  is stored in the sampler source swizzle x.
+
 .. math::
 
    coord = src0
 
+   (without TGSI_TG4_COMPONENT_IN_SWIZZLE)
    component = src1
 
    dst = texture\_gather4 (unit, coord, component)
 
+   (with TGSI_TG4_COMPONENT_IN_SWIZZLE)
+   dst = texture\_gather4 (unit, coord)
+   component is encoded in sampler swizzle.
+
 (with SM5 - cube array shadow)
 
 .. math::

diff --git a/src/gallium/include/pipe/p_defines.h b/src/gallium/include/pipe/p_defines.h
index 564f37dd1b578312c785b59f45ffc1f1a20d111e..6657271cbf673131c4809d1056c770cdbda1b223 100644 (file)
--- a/src/gallium/include/pipe/p_defines.h
+++ b/src/gallium/include/pipe/p_defines.h
@@ -903,6 +903,7 @@ enum pipe_cap
    PIPE_CAP_GL_SPIRV,
    PIPE_CAP_GL_SPIRV_VARIABLE_POINTERS,
    PIPE_CAP_DEMOTE_TO_HELPER_INVOCATION,
+   PIPE_CAP_TGSI_TG4_COMPONENT_IN_SWIZZLE,
 };
 
 /**