svga: add/use new svga_sampler_format() function

This is important for the case of sampling from a depth texture.  In
that case, we need to sample the texture as if it were a single-channel
color texture.  For other/color formats, we can use the format as-is.

Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Reviewed-by: José Fonseca <jfonseca@vmware.com>

src/gallium/drivers/svga/svga_format.c

@@ -2098,3 +2098,26 @@ svga_typeless_format(SVGA3dSurfaceFormat format)
       return format;
    }
 }
+
+
+/**
+ * Given a surface format, return the corresponding format to use for
+ * a texture sampler.  In most cases, it's the format unchanged, but there
+ * are some special cases.
+ */
+SVGA3dSurfaceFormat
+svga_sampler_format(SVGA3dSurfaceFormat format)
+{
+   switch (format) {
+   case SVGA3D_D16_UNORM:
+      return SVGA3D_R16_UNORM;
+   case SVGA3D_D24_UNORM_S8_UINT:
+      return SVGA3D_R24_UNORM_X8_TYPELESS;
+   case SVGA3D_D32_FLOAT:
+      return SVGA3D_R32_FLOAT;
+   case SVGA3D_D32_FLOAT_S8X24_UINT:
+      return SVGA3D_R32_FLOAT_X8X24_TYPELESS;
+   default:
+      return format;
+   }
+}

src/gallium/drivers/svga/svga_format.h

@@ -93,4 +93,8 @@ SVGA3dSurfaceFormat
 svga_typeless_format(SVGA3dSurfaceFormat format);
 
 
+SVGA3dSurfaceFormat
+svga_sampler_format(SVGA3dSurfaceFormat format);
+
+
 #endif /* SVGA_FORMAT_H_ */

src/gallium/drivers/svga/svga_state_sampler.c

@@ -108,6 +108,9 @@ svga_validate_pipe_sampler_view(struct svga_context *svga,
                                      PIPE_BIND_SAMPLER_VIEW);
       assert(format != SVGA3D_FORMAT_INVALID);
 
+      /* Convert the format to a sampler-friendly format, if needed */
+      format = svga_sampler_format(format);
+
       if (texture->target == PIPE_BUFFER) {
          viewDesc.buffer.firstElement = sv->base.u.buf.first_element;
          viewDesc.buffer.numElements = (sv->base.u.buf.last_element -