st/mesa: Gallium support for ARB_fragment_coord_conventions (v4)

Changes in v4;
- Implemented Brian Paul's style suggestions

Changes in v3:
- Use positive caps instead of negative ones

Changes in v2:
- Updated formatting

The state tracker will use the TGSI convention properties if the hardware
exposes the appropriate capability, and otherwise adjust WPOS itself.

This will also fix some drivers that were previously broken due to their
incorrect, inadvertent, use of conventions other than upper_left+half_integer.

2 files changed, 72 insertions, 3 deletions

diff --git a/src/mesa/state_tracker/st_extensions.c b/src/mesa/state_tracker/st_extensions.c
index 31c03c07835..f2a62f9b690 100644
--- a/src/mesa/state_tracker/st_extensions.c
+++ b/src/mesa/state_tracker/st_extensions.c
@@ -147,6 +147,7 @@ void st_init_extensions(struct st_context *st)
     * Extensions that are supported by all Gallium drivers:
     */
    ctx->Extensions.ARB_copy_buffer = GL_TRUE;
+   ctx->Extensions.ARB_fragment_coord_conventions = GL_TRUE;
    ctx->Extensions.ARB_fragment_program = GL_TRUE;
    ctx->Extensions.ARB_map_buffer_range = GL_TRUE;
    ctx->Extensions.ARB_multisample = GL_TRUE;
diff --git a/src/mesa/state_tracker/st_mesa_to_tgsi.c b/src/mesa/state_tracker/st_mesa_to_tgsi.c
index 05b56c9b584..4aed2df8c31 100644
--- a/src/mesa/state_tracker/st_mesa_to_tgsi.c
+++ b/src/mesa/state_tracker/st_mesa_to_tgsi.c
@@ -34,8 +34,10 @@
 #include "pipe/p_compiler.h"
 #include "pipe/p_shader_tokens.h"
 #include "pipe/p_state.h"
+#include "pipe/p_context.h"
 #include "tgsi/tgsi_ureg.h"
 #include "st_mesa_to_tgsi.h"
+#include "st_context.h"
 #include "shader/prog_instruction.h"
 #include "shader/prog_parameter.h"
 #include "shader/prog_print.h"
@@ -665,6 +667,22 @@ compile_instruction(
    }
 }
 
+/**
+ * Emit the TGSI instructions to adjust the WPOS pixel center convention
+ */
+static void
+emit_adjusted_wpos( struct st_translate *t,
+                    const struct gl_program *program, GLfloat value)
+{
+   struct ureg_program *ureg = t->ureg;
+   struct ureg_dst wpos_temp = ureg_DECL_temporary(ureg);
+   struct ureg_src wpos_input = t->inputs[t->inputMapping[FRAG_ATTRIB_WPOS]];
+
+   ureg_ADD(ureg, ureg_writemask(wpos_temp, TGSI_WRITEMASK_X | TGSI_WRITEMASK_Y),
+		   wpos_input, ureg_imm1f(ureg, value));
+
+   t->inputs[t->inputMapping[FRAG_ATTRIB_WPOS]] = ureg_src(wpos_temp);
+}
 
 /**
  * Emit the TGSI instructions for inverting the WPOS y coordinate.
@@ -690,12 +708,17 @@ emit_inverted_wpos( struct st_translate *t,
                                                        winSizeState);
 
    struct ureg_src winsize = ureg_DECL_constant( ureg, winHeightConst );
-   struct ureg_dst wpos_temp = ureg_DECL_temporary( ureg );
+   struct ureg_dst wpos_temp;
    struct ureg_src wpos_input = t->inputs[t->inputMapping[FRAG_ATTRIB_WPOS]];
 
    /* MOV wpos_temp, input[wpos]
     */
-   ureg_MOV( ureg, wpos_temp, wpos_input );
+   if (wpos_input.File == TGSI_FILE_TEMPORARY)
+      wpos_temp = ureg_dst(wpos_input);
+   else {
+      wpos_temp = ureg_DECL_temporary( ureg );
+      ureg_MOV( ureg, wpos_temp, wpos_input );
+   }
 
    /* SUB wpos_temp.y, winsize_const, wpos_input
     */
@@ -801,6 +824,7 @@ st_translate_mesa_program(
     * Declare input attributes.
     */
    if (procType == TGSI_PROCESSOR_FRAGMENT) {
+      struct gl_fragment_program* fp = (struct gl_fragment_program*)program;
       for (i = 0; i < numInputs; i++) {
          t->inputs[i] = ureg_DECL_fs_input(ureg,
                                            inputSemanticName[i],
@@ -812,7 +836,51 @@ st_translate_mesa_program(
          /* Must do this after setting up t->inputs, and before
           * emitting constant references, below:
           */
-         emit_inverted_wpos( t, program );
+         struct pipe_screen* pscreen = st_context(ctx)->pipe->screen;
+         boolean invert = FALSE;
+
+         if (fp->OriginUpperLeft) {
+            if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_UPPER_LEFT)) {
+            }
+            else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT)) {
+               ureg_property_fs_coord_origin(ureg, TGSI_FS_COORD_ORIGIN_LOWER_LEFT);
+               invert = TRUE;
+            }
+            else
+               assert(0);
+         }
+         else {
+            if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT))
+               ureg_property_fs_coord_origin(ureg, TGSI_FS_COORD_ORIGIN_LOWER_LEFT);
+            else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_UPPER_LEFT))
+               invert = TRUE;
+            else
+               assert(0);
+         }
+
+         if (fp->PixelCenterInteger) {
+            if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER))
+               ureg_property_fs_coord_pixel_center(ureg, TGSI_FS_COORD_PIXEL_CENTER_INTEGER);
+            else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER))
+               emit_adjusted_wpos(t, program, invert ? 0.5f : -0.5f);
+            else
+               assert(0);
+         }
+         else {
+            if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER)) {
+            }
+            else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER)) {
+               ureg_property_fs_coord_pixel_center(ureg, TGSI_FS_COORD_PIXEL_CENTER_INTEGER);
+               emit_adjusted_wpos(t, program, invert ? -0.5f : 0.5f);
+            }
+            else
+               assert(0);
+         }
+
+         /* we invert after adjustment so that we avoid the MOV to temporary,
+          * and reuse the adjustment ADD instead */
+         if (invert)
+            emit_inverted_wpos(t, program);
       }
 
       if (program->InputsRead & FRAG_BIT_FACE) {