mesa/st: Backport WPOS adjustment fixes from st_mesa_to_tgsi.c to st_glsl_to_tgsi.cpp.

This is a trivial verbatim copy of the code from Christoph Bumiller's commit
f986a6560f3ee9a79b89e9409e3a9ac52b53315c.

Fixes fdo 39939 and 39942.

1 files changed, 83 insertions, 51 deletions

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index 18e8a1db44e..35fd1ffc13a 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -4322,37 +4322,15 @@ compile_tgsi_instruction(struct st_translate *t,
 }
 
 /**
- * Emit the TGSI instructions to adjust the WPOS pixel center convention
- * Basically, add (adjX, adjY) to the fragment position.
- */
-static void
-emit_adjusted_wpos(struct st_translate *t,
-                   const struct gl_program *program,
-                   float adjX, float adjY)
-{
-   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]];
-
-   /* Note that we bias X and Y and pass Z and W through unchanged.
-    * The shader might also use gl_FragCoord.w and .z.
-    */
-   ureg_ADD(ureg, wpos_temp, wpos_input,
-            ureg_imm4f(ureg, adjX, adjY, 0.0f, 0.0f));
-
-   t->inputs[t->inputMapping[FRAG_ATTRIB_WPOS]] = ureg_src(wpos_temp);
-}
-
-
-/**
- * Emit the TGSI instructions for inverting the WPOS y coordinate.
+ * Emit the TGSI instructions for inverting and adjusting WPOS.
  * This code is unavoidable because it also depends on whether
  * a FBO is bound (STATE_FB_WPOS_Y_TRANSFORM).
  */
 static void
-emit_wpos_inversion(struct st_translate *t,
-                    const struct gl_program *program,
-                    bool invert)
+emit_wpos_adjustment( struct st_translate *t,
+                      const struct gl_program *program,
+                      boolean invert,
+                      GLfloat adjX, GLfloat adjY[2])
 {
    struct ureg_program *ureg = t->ureg;
 
@@ -4371,35 +4349,55 @@ emit_wpos_inversion(struct st_translate *t,
    unsigned wposTransConst = _mesa_add_state_reference(program->Parameters,
                                                        wposTransformState);
 
-   struct ureg_src wpostrans = ureg_DECL_constant(ureg, wposTransConst);
-   struct ureg_dst wpos_temp;
+   struct ureg_src wpostrans = ureg_DECL_constant( ureg, wposTransConst );
+   struct ureg_dst wpos_temp = ureg_DECL_temporary( ureg );
    struct ureg_src wpos_input = t->inputs[t->inputMapping[FRAG_ATTRIB_WPOS]];
 
-   /* MOV wpos_temp, input[wpos]
-    */
-   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);
+   /* First, apply the coordinate shift: */
+   if (adjX || adjY[0] || adjY[1]) {
+      if (adjY[0] != adjY[1]) {
+         /* Adjust the y coordinate by adjY[1] or adjY[0] respectively
+          * depending on whether inversion is actually going to be applied
+          * or not, which is determined by testing against the inversion
+          * state variable used below, which will be either +1 or -1.
+          */
+         struct ureg_dst adj_temp = ureg_DECL_temporary(ureg);
+
+         ureg_CMP(ureg, adj_temp,
+                  ureg_scalar(wpostrans, invert ? 2 : 0),
+                  ureg_imm4f(ureg, adjX, adjY[0], 0.0f, 0.0f),
+                  ureg_imm4f(ureg, adjX, adjY[1], 0.0f, 0.0f));
+         ureg_ADD(ureg, wpos_temp, wpos_input, ureg_src(adj_temp));
+      } else {
+         ureg_ADD(ureg, wpos_temp, wpos_input,
+                  ureg_imm4f(ureg, adjX, adjY[0], 0.0f, 0.0f));
+      }
+      wpos_input = ureg_src(wpos_temp);
+   } else {
+      /* MOV wpos_temp, input[wpos]
+       */
+      ureg_MOV( ureg, wpos_temp, wpos_input );
    }
 
+   /* Now the conditional y flip: STATE_FB_WPOS_Y_TRANSFORM.xy/zw will be
+    * inversion/identity, or the other way around if we're drawing to an FBO.
+    */
    if (invert) {
       /* MAD wpos_temp.y, wpos_input, wpostrans.xxxx, wpostrans.yyyy
        */
-      ureg_MAD(ureg,
-               ureg_writemask(wpos_temp, TGSI_WRITEMASK_Y),
-               wpos_input,
-               ureg_scalar(wpostrans, 0),
-               ureg_scalar(wpostrans, 1));
+      ureg_MAD( ureg,
+                ureg_writemask(wpos_temp, TGSI_WRITEMASK_Y ),
+                wpos_input,
+                ureg_scalar(wpostrans, 0),
+                ureg_scalar(wpostrans, 1));
    } else {
       /* MAD wpos_temp.y, wpos_input, wpostrans.zzzz, wpostrans.wwww
        */
-      ureg_MAD(ureg,
-               ureg_writemask(wpos_temp, TGSI_WRITEMASK_Y),
-               wpos_input,
-               ureg_scalar(wpostrans, 2),
-               ureg_scalar(wpostrans, 3));
+      ureg_MAD( ureg,
+                ureg_writemask(wpos_temp, TGSI_WRITEMASK_Y ),
+                wpos_input,
+                ureg_scalar(wpostrans, 2),
+                ureg_scalar(wpostrans, 3));
    }
 
    /* Use wpos_temp as position input from here on:
@@ -4420,8 +4418,37 @@ emit_wpos(struct st_context *st,
    const struct gl_fragment_program *fp =
       (const struct gl_fragment_program *) program;
    struct pipe_screen *pscreen = st->pipe->screen;
+   GLfloat adjX = 0.0f;
+   GLfloat adjY[2] = { 0.0f, 0.0f };
    boolean invert = FALSE;
 
+   /* Query the pixel center conventions supported by the pipe driver and set
+    * adjX, adjY to help out if it cannot handle the requested one internally.
+    *
+    * The bias of the y-coordinate depends on whether y-inversion takes place
+    * (adjY[1]) or not (adjY[0]), which is in turn dependent on whether we are
+    * drawing to an FBO (causes additional inversion), and whether the the pipe
+    * driver origin and the requested origin differ (the latter condition is
+    * stored in the 'invert' variable).
+    *
+    * For height = 100 (i = integer, h = half-integer, l = lower, u = upper):
+    *
+    * center shift only:
+    * i -> h: +0.5
+    * h -> i: -0.5
+    *
+    * inversion only:
+    * l,i -> u,i: ( 0.0 + 1.0) * -1 + 100 = 99
+    * l,h -> u,h: ( 0.5 + 0.0) * -1 + 100 = 99.5
+    * u,i -> l,i: (99.0 + 1.0) * -1 + 100 = 0
+    * u,h -> l,h: (99.5 + 0.0) * -1 + 100 = 0.5
+    *
+    * inversion and center shift:
+    * l,i -> u,h: ( 0.0 + 0.5) * -1 + 100 = 99.5
+    * l,h -> u,i: ( 0.5 + 0.5) * -1 + 100 = 99
+    * u,i -> l,h: (99.0 + 0.5) * -1 + 100 = 0.5
+    * u,h -> l,i: (99.5 + 0.5) * -1 + 100 = 0
+    */
    if (fp->OriginUpperLeft) {
       /* Fragment shader wants origin in upper-left */
       if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_UPPER_LEFT)) {
@@ -4449,12 +4476,17 @@ emit_wpos(struct st_context *st,
    
    if (fp->PixelCenterInteger) {
       /* Fragment shader wants pixel center integer */
-      if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER))
+      if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER)) {
          /* the driver supports pixel center integer */
+         adjY[1] = 1.0f;
          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))
+      }
+      else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER)) {
          /* the driver supports pixel center half integer, need to bias X,Y */
-         emit_adjusted_wpos(t, program, 0.5f, invert ? 0.5f : -0.5f);
+         adjX = -0.5f;
+         adjY[0] = -0.5f;
+         adjY[1] = 0.5f;
+      }
       else
          assert(0);
    }
@@ -4465,8 +4497,8 @@ emit_wpos(struct st_context *st,
       }
       else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER)) {
          /* the driver supports pixel center integer, need to bias X,Y */
+         adjX = adjY[0] = adjY[1] = 0.5f;
          ureg_property_fs_coord_pixel_center(ureg, TGSI_FS_COORD_PIXEL_CENTER_INTEGER);
-         emit_adjusted_wpos(t, program, 0.5f, invert ? -0.5f : 0.5f);
       }
       else
          assert(0);
@@ -4474,7 +4506,7 @@ emit_wpos(struct st_context *st,
 
    /* we invert after adjustment so that we avoid the MOV to temporary,
     * and reuse the adjustment ADD instead */
-   emit_wpos_inversion(t, program, invert);
+   emit_wpos_adjustment(t, program, invert, adjX, adjY);
 }
 
 /**