gallium: Add PIPE_SHADER_CAP_DOUBLES

This is for reporting whether or not double precision floating-point
operations are supported.

Reviewed-by: Francisco Jerez <currojerez@riseup.net>

src/gallium/auxiliary/gallivm/lp_bld_limits.h

@@ -126,6 +126,8 @@ gallivm_get_shader_param(enum pipe_shader_cap param)
       return PIPE_SHADER_IR_TGSI;
    case PIPE_SHADER_CAP_TGSI_SQRT_SUPPORTED:
       return 1;
+   case PIPE_SHADER_CAP_DOUBLES:
+      return 0;
    }
    /* if we get here, we missed a shader cap above (and should have seen
     * a compiler warning.)

src/gallium/auxiliary/tgsi/tgsi_exec.h

@@ -456,6 +456,8 @@ tgsi_exec_get_shader_param(enum pipe_shader_cap param)
       return PIPE_SHADER_IR_TGSI;
    case PIPE_SHADER_CAP_TGSI_SQRT_SUPPORTED:
       return 1;
+   case PIPE_SHADER_CAP_DOUBLES:
+      return 0;
    }
    /* if we get here, we missed a shader cap above (and should have seen
     * a compiler warning.)

src/gallium/docs/source/screen.rst

@@ -288,6 +288,8 @@ to be 0.
   program.  It should be one of the ``pipe_shader_ir`` enum values.
 * ``PIPE_SHADER_CAP_MAX_SAMPLER_VIEWS``: The maximum number of texture
   sampler views. Must not be lower than PIPE_SHADER_CAP_MAX_TEXTURE_SAMPLERS.
+* ``PIPE_SHADER_CAP_DOUBLES``: Whether double precision floating-point
+  operations are supported.
 
 
 .. _pipe_compute_cap:

src/gallium/drivers/r600/r600_pipe.c

@@ -447,6 +447,8 @@ static int r600_get_shader_param(struct pipe_screen* pscreen, unsigned shader, e
 		} else {
 			return PIPE_SHADER_IR_TGSI;
 		}
+	case PIPE_SHADER_CAP_DOUBLES:
+		return 0;
 	}
 	return 0;
 }

src/gallium/drivers/radeonsi/si_pipe.c

@@ -327,6 +327,9 @@ static int si_get_shader_param(struct pipe_screen* pscreen, unsigned shader, enu
 		switch (param) {
 		case PIPE_SHADER_CAP_PREFERRED_IR:
 			return PIPE_SHADER_IR_LLVM;
+		case PIPE_SHADER_CAP_DOUBLES:
+			return 0; /* XXX: Enable doubles once the compiler can
+			             handle them. */
 		default:
 			return 0;
 		}
@@ -378,6 +381,8 @@ static int si_get_shader_param(struct pipe_screen* pscreen, unsigned shader, enu
 		return 16;
 	case PIPE_SHADER_CAP_PREFERRED_IR:
 		return PIPE_SHADER_IR_TGSI;
+	case PIPE_SHADER_CAP_DOUBLES:
+		return 0;
 	}
 	return 0;
 }

src/gallium/include/pipe/p_defines.h

@@ -620,7 +620,8 @@ enum pipe_shader_cap
    PIPE_SHADER_CAP_MAX_TEXTURE_SAMPLERS,
    PIPE_SHADER_CAP_PREFERRED_IR,
    PIPE_SHADER_CAP_TGSI_SQRT_SUPPORTED,
-   PIPE_SHADER_CAP_MAX_SAMPLER_VIEWS
+   PIPE_SHADER_CAP_MAX_SAMPLER_VIEWS,
+   PIPE_SHADER_CAP_DOUBLES
 };
 
 /**