Merge commit 'origin/master' into gallium-0.2

Conflicts:

	progs/glsl/Makefile

1 files changed, 477 insertions, 541 deletions

diff --git a/src/mesa/swrast/s_texfilter.c b/src/mesa/swrast/s_texfilter.c
index 9e44fba3da..6b1dfd5d50 100644
--- a/src/mesa/swrast/s_texfilter.c
+++ b/src/mesa/swrast/s_texfilter.c
@@ -1,8 +1,8 @@
 /*
  * Mesa 3-D graphics library
- * Version:  7.0.3
+ * Version:  7.3
  *
- * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
+ * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -33,6 +33,16 @@
 #include "s_texfilter.h"
 
 
+/*
+ * Note, the FRAC macro has to work perfectly.  Otherwise you'll sometimes
+ * see 1-pixel bands of improperly weighted linear-filtered textures.
+ * The tests/texwrap.c demo is a good test.
+ * Also note, FRAC(x) doesn't truly return the fractional part of x for x < 0.
+ * Instead, if x < 0 then FRAC(x) = 1 - true_frac(x).
+ */
+#define FRAC(f)  ((f) - IFLOOR(f))
+
+
 /**
  * Constants for integer linear interpolation.
  */
@@ -223,257 +233,271 @@ lerp_rgba_3d(GLchan result[4], GLfloat a, GLfloat b, GLfloat c,
  * Used to compute texel locations for linear sampling.
  * Input:
  *    wrapMode = GL_REPEAT, GL_CLAMP, GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER
- *    S = texcoord in [0,1]
- *    SIZE = width (or height or depth) of texture
+ *    s = texcoord in [0,1]
+ *    size = width (or height or depth) of texture
  * Output:
- *    U = texcoord in [0, width]
- *    I0, I1 = two nearest texel indexes
+ *    i0, i1 = returns two nearest texel indexes
+ *    weight = returns blend factor between texels
  */
-#define COMPUTE_LINEAR_TEXEL_LOCATIONS(wrapMode, S, U, SIZE, I0, I1)	\
-{									\
-   switch (wrapMode) {							\
-   case GL_REPEAT:							\
-      U = S * SIZE - 0.5F;						\
-      if (img->_IsPowerOfTwo) {						\
-         I0 = IFLOOR(U) & (SIZE - 1);					\
-         I1 = (I0 + 1) & (SIZE - 1);					\
-      }									\
-      else {								\
-         I0 = REMAINDER(IFLOOR(U), SIZE);				\
-         I1 = REMAINDER(I0 + 1, SIZE);					\
-      }									\
-      break;								\
-   case GL_CLAMP_TO_EDGE:						\
-      if (S <= 0.0F)							\
-         U = 0.0F;							\
-      else if (S >= 1.0F)						\
-         U = (GLfloat) SIZE;						\
-      else								\
-         U = S * SIZE;							\
-      U -= 0.5F;							\
-      I0 = IFLOOR(U);							\
-      I1 = I0 + 1;							\
-      if (I0 < 0)							\
-         I0 = 0;							\
-      if (I1 >= (GLint) SIZE)						\
-         I1 = SIZE - 1;							\
-      break;								\
-   case GL_CLAMP_TO_BORDER:						\
-      {									\
-         const GLfloat min = -1.0F / (2.0F * SIZE);			\
-         const GLfloat max = 1.0F - min;				\
-         if (S <= min)							\
-            U = min * SIZE;						\
-         else if (S >= max)						\
-            U = max * SIZE;						\
-         else								\
-            U = S * SIZE;						\
-         U -= 0.5F;							\
-         I0 = IFLOOR(U);						\
-         I1 = I0 + 1;							\
-      }									\
-      break;								\
-   case GL_MIRRORED_REPEAT:						\
-      {									\
-         const GLint flr = IFLOOR(S);					\
-         if (flr & 1)							\
-            U = 1.0F - (S - (GLfloat) flr);	/* flr is odd */	\
-         else								\
-            U = S - (GLfloat) flr;		/* flr is even */	\
-         U = (U * SIZE) - 0.5F;						\
-         I0 = IFLOOR(U);						\
-         I1 = I0 + 1;							\
-         if (I0 < 0)							\
-            I0 = 0;							\
-         if (I1 >= (GLint) SIZE)					\
-            I1 = SIZE - 1;						\
-      }									\
-      break;								\
-   case GL_MIRROR_CLAMP_EXT:						\
-      U = FABSF(S);							\
-      if (U >= 1.0F)							\
-         U = (GLfloat) SIZE;						\
-      else								\
-         U *= SIZE;							\
-      U -= 0.5F;							\
-      I0 = IFLOOR(U);							\
-      I1 = I0 + 1;							\
-      break;								\
-   case GL_MIRROR_CLAMP_TO_EDGE_EXT:					\
-      U = FABSF(S);							\
-      if (U >= 1.0F)							\
-         U = (GLfloat) SIZE;						\
-      else								\
-         U *= SIZE;							\
-      U -= 0.5F;							\
-      I0 = IFLOOR(U);							\
-      I1 = I0 + 1;							\
-      if (I0 < 0)							\
-         I0 = 0;							\
-      if (I1 >= (GLint) SIZE)						\
-         I1 = SIZE - 1;							\
-      break;								\
-   case GL_MIRROR_CLAMP_TO_BORDER_EXT:					\
-      {									\
-         const GLfloat min = -1.0F / (2.0F * SIZE);			\
-         const GLfloat max = 1.0F - min;				\
-         U = FABSF(S);							\
-         if (U <= min)							\
-            U = min * SIZE;						\
-         else if (U >= max)						\
-            U = max * SIZE;						\
-         else								\
-            U *= SIZE;							\
-         U -= 0.5F;							\
-         I0 = IFLOOR(U);						\
-         I1 = I0 + 1;							\
-      }									\
-      break;								\
-   case GL_CLAMP:							\
-      if (S <= 0.0F)							\
-         U = 0.0F;							\
-      else if (S >= 1.0F)						\
-         U = (GLfloat) SIZE;						\
-      else								\
-         U = S * SIZE;							\
-      U -= 0.5F;							\
-      I0 = IFLOOR(U);							\
-      I1 = I0 + 1;							\
-      break;								\
-   default:								\
-      _mesa_problem(ctx, "Bad wrap mode");				\
-      return;								\
-   }									\
+static INLINE void
+linear_texel_locations(GLenum wrapMode,
+                       const struct gl_texture_image *img,
+                       GLint size, GLfloat s,
+                       GLint *i0, GLint *i1, GLfloat *weight)
+{
+   GLfloat u;
+   switch (wrapMode) {
+   case GL_REPEAT:
+      u = s * size - 0.5F;
+      if (img->_IsPowerOfTwo) {
+         *i0 = IFLOOR(u) & (size - 1);
+         *i1 = (*i0 + 1) & (size - 1);
+      }
+      else {
+         *i0 = REMAINDER(IFLOOR(u), size);
+         *i1 = REMAINDER(*i0 + 1, size);
+      }
+      break;
+   case GL_CLAMP_TO_EDGE:
+      if (s <= 0.0F)
+         u = 0.0F;
+      else if (s >= 1.0F)
+         u = (GLfloat) size;
+      else
+         u = s * size;
+      u -= 0.5F;
+      *i0 = IFLOOR(u);
+      *i1 = *i0 + 1;
+      if (*i0 < 0)
+         *i0 = 0;
+      if (*i1 >= (GLint) size)
+         *i1 = size - 1;
+      break;
+   case GL_CLAMP_TO_BORDER:
+      {
+         const GLfloat min = -1.0F / (2.0F * size);
+         const GLfloat max = 1.0F - min;
+         if (s <= min)
+            u = min * size;
+         else if (s >= max)
+            u = max * size;
+         else
+            u = s * size;
+         u -= 0.5F;
+         *i0 = IFLOOR(u);
+         *i1 = *i0 + 1;
+      }
+      break;
+   case GL_MIRRORED_REPEAT:
+      {
+         const GLint flr = IFLOOR(s);
+         if (flr & 1)
+            u = 1.0F - (s - (GLfloat) flr);
+         else
+            u = s - (GLfloat) flr;
+         u = (u * size) - 0.5F;
+         *i0 = IFLOOR(u);
+         *i1 = *i0 + 1;
+         if (*i0 < 0)
+            *i0 = 0;
+         if (*i1 >= (GLint) size)
+            *i1 = size - 1;
+      }
+      break;
+   case GL_MIRROR_CLAMP_EXT:
+      u = FABSF(s);
+      if (u >= 1.0F)
+         u = (GLfloat) size;
+      else
+         u *= size;
+      u -= 0.5F;
+      *i0 = IFLOOR(u);
+      *i1 = *i0 + 1;
+      break;
+   case GL_MIRROR_CLAMP_TO_EDGE_EXT:
+      u = FABSF(s);
+      if (u >= 1.0F)
+         u = (GLfloat) size;
+      else
+         u *= size;
+      u -= 0.5F;
+      *i0 = IFLOOR(u);
+      *i1 = *i0 + 1;
+      if (*i0 < 0)
+         *i0 = 0;
+      if (*i1 >= (GLint) size)
+         *i1 = size - 1;
+      break;
+   case GL_MIRROR_CLAMP_TO_BORDER_EXT:
+      {
+         const GLfloat min = -1.0F / (2.0F * size);
+         const GLfloat max = 1.0F - min;
+         u = FABSF(s);
+         if (u <= min)
+            u = min * size;
+         else if (u >= max)
+            u = max * size;
+         else
+            u *= size;
+         u -= 0.5F;
+         *i0 = IFLOOR(u);
+         *i1 = *i0 + 1;
+      }
+      break;
+   case GL_CLAMP:
+      if (s <= 0.0F)
+         u = 0.0F;
+      else if (s >= 1.0F)
+         u = (GLfloat) size;
+      else
+         u = s * size;
+      u -= 0.5F;
+      *i0 = IFLOOR(u);
+      *i1 = *i0 + 1;
+      break;
+   default:
+      _mesa_problem(NULL, "Bad wrap mode");
+      u = 0.0F;
+   }
+   *weight = FRAC(u);
 }
 
 
 /**
  * Used to compute texel location for nearest sampling.
  */
-#define COMPUTE_NEAREST_TEXEL_LOCATION(wrapMode, S, SIZE, I)		\
-{									\
-   switch (wrapMode) {							\
-   case GL_REPEAT:							\
-      /* s limited to [0,1) */						\
-      /* i limited to [0,size-1] */					\
-      I = IFLOOR(S * SIZE);						\
-      if (img->_IsPowerOfTwo)						\
-         I &= (SIZE - 1);						\
-      else								\
-         I = REMAINDER(I, SIZE);					\
-      break;								\
-   case GL_CLAMP_TO_EDGE:						\
-      {									\
-         /* s limited to [min,max] */					\
-         /* i limited to [0, size-1] */					\
-         const GLfloat min = 1.0F / (2.0F * SIZE);			\
-         const GLfloat max = 1.0F - min;				\
-         if (S < min)							\
-            I = 0;							\
-         else if (S > max)						\
-            I = SIZE - 1;						\
-         else								\
-            I = IFLOOR(S * SIZE);					\
-      }									\
-      break;								\
-   case GL_CLAMP_TO_BORDER:						\
-      {									\
-         /* s limited to [min,max] */					\
-         /* i limited to [-1, size] */					\
-         const GLfloat min = -1.0F / (2.0F * SIZE);			\
-         const GLfloat max = 1.0F - min;				\
-         if (S <= min)							\
-            I = -1;							\
-         else if (S >= max)						\
-            I = SIZE;							\
-         else								\
-            I = IFLOOR(S * SIZE);					\
-      }									\
-      break;								\
-   case GL_MIRRORED_REPEAT:						\
-      {									\
-         const GLfloat min = 1.0F / (2.0F * SIZE);			\
-         const GLfloat max = 1.0F - min;				\
-         const GLint flr = IFLOOR(S);					\
-         GLfloat u;							\
-         if (flr & 1)							\
-            u = 1.0F - (S - (GLfloat) flr);	/* flr is odd */	\
-         else								\
-            u = S - (GLfloat) flr;		/* flr is even */	\
-         if (u < min)							\
-            I = 0;							\
-         else if (u > max)						\
-            I = SIZE - 1;						\
-         else								\
-            I = IFLOOR(u * SIZE);					\
-      }									\
-      break;								\
-   case GL_MIRROR_CLAMP_EXT:						\
-      {									\
-         /* s limited to [0,1] */					\
-         /* i limited to [0,size-1] */					\
-         const GLfloat u = FABSF(S);					\
-         if (u <= 0.0F)							\
-            I = 0;							\
-         else if (u >= 1.0F)						\
-            I = SIZE - 1;						\
-         else								\
-            I = IFLOOR(u * SIZE);					\
-      }									\
-      break;								\
-   case GL_MIRROR_CLAMP_TO_EDGE_EXT:					\
-      {									\
-         /* s limited to [min,max] */					\
-         /* i limited to [0, size-1] */					\
-         const GLfloat min = 1.0F / (2.0F * SIZE);			\
-         const GLfloat max = 1.0F - min;				\
-         const GLfloat u = FABSF(S);					\
-         if (u < min)							\
-            I = 0;							\
-         else if (u > max)						\
-            I = SIZE - 1;						\
-         else								\
-            I = IFLOOR(u * SIZE);					\
-      }									\
-      break;								\
-   case GL_MIRROR_CLAMP_TO_BORDER_EXT:					\
-      {									\
-         /* s limited to [min,max] */					\
-         /* i limited to [0, size-1] */					\
-         const GLfloat min = -1.0F / (2.0F * SIZE);			\
-         const GLfloat max = 1.0F - min;				\
-         const GLfloat u = FABSF(S);					\
-         if (u < min)							\
-            I = -1;							\
-         else if (u > max)						\
-            I = SIZE;							\
-         else								\
-            I = IFLOOR(u * SIZE);					\
-      }									\
-      break;								\
-   case GL_CLAMP:							\
-      /* s limited to [0,1] */						\
-      /* i limited to [0,size-1] */					\
-      if (S <= 0.0F)							\
-         I = 0;								\
-      else if (S >= 1.0F)						\
-         I = SIZE - 1;							\
-      else								\
-         I = IFLOOR(S * SIZE);						\
-      break;								\
-   default:								\
-      _mesa_problem(ctx, "Bad wrap mode");				\
-      return;								\
-   }									\
+static INLINE GLint
+nearest_texel_location(GLenum wrapMode,
+                       const struct gl_texture_image *img,
+                       GLint size, GLfloat s)
+{
+   GLint i;
+
+   switch (wrapMode) {
+   case GL_REPEAT:
+      /* s limited to [0,1) */
+      /* i limited to [0,size-1] */
+      i = IFLOOR(s * size);
+      if (img->_IsPowerOfTwo)
+         i &= (size - 1);
+      else
+         i = REMAINDER(i, size);
+      return i;
+   case GL_CLAMP_TO_EDGE:
+      {
+         /* s limited to [min,max] */
+         /* i limited to [0, size-1] */
+         const GLfloat min = 1.0F / (2.0F * size);
+         const GLfloat max = 1.0F - min;
+         if (s < min)
+            i = 0;
+         else if (s > max)
+            i = size - 1;
+         else
+            i = IFLOOR(s * size);
+      }
+      return i;
+   case GL_CLAMP_TO_BORDER:
+      {
+         /* s limited to [min,max] */
+         /* i limited to [-1, size] */
+         const GLfloat min = -1.0F / (2.0F * size);
+         const GLfloat max = 1.0F - min;
+         if (s <= min)
+            i = -1;
+         else if (s >= max)
+            i = size;
+         else
+            i = IFLOOR(s * size);
+      }
+      return i;
+   case GL_MIRRORED_REPEAT:
+      {
+         const GLfloat min = 1.0F / (2.0F * size);
+         const GLfloat max = 1.0F - min;
+         const GLint flr = IFLOOR(s);
+         GLfloat u;
+         if (flr & 1)
+            u = 1.0F - (s - (GLfloat) flr);
+         else
+            u = s - (GLfloat) flr;
+         if (u < min)
+            i = 0;
+         else if (u > max)
+            i = size - 1;
+         else
+            i = IFLOOR(u * size);
+      }
+      return i;
+   case GL_MIRROR_CLAMP_EXT:
+      {
+         /* s limited to [0,1] */
+         /* i limited to [0,size-1] */
+         const GLfloat u = FABSF(s);
+         if (u <= 0.0F)
+            i = 0;
+         else if (u >= 1.0F)
+            i = size - 1;
+         else
+            i = IFLOOR(u * size);
+      }
+      return i;
+   case GL_MIRROR_CLAMP_TO_EDGE_EXT:
+      {
+         /* s limited to [min,max] */
+         /* i limited to [0, size-1] */
+         const GLfloat min = 1.0F / (2.0F * size);
+         const GLfloat max = 1.0F - min;
+         const GLfloat u = FABSF(s);
+         if (u < min)
+            i = 0;
+         else if (u > max)
+            i = size - 1;
+         else
+            i = IFLOOR(u * size);
+      }
+      return i;
+   case GL_MIRROR_CLAMP_TO_BORDER_EXT:
+      {
+         /* s limited to [min,max] */
+         /* i limited to [0, size-1] */
+         const GLfloat min = -1.0F / (2.0F * size);
+         const GLfloat max = 1.0F - min;
+         const GLfloat u = FABSF(s);
+         if (u < min)
+            i = -1;
+         else if (u > max)
+            i = size;
+         else
+            i = IFLOOR(u * size);
+      }
+      return i;
+   case GL_CLAMP:
+      /* s limited to [0,1] */
+      /* i limited to [0,size-1] */
+      if (s <= 0.0F)
+         i = 0;
+      else if (s >= 1.0F)
+         i = size - 1;
+      else
+         i = IFLOOR(s * size);
+      return i;
+   default:
+      _mesa_problem(NULL, "Bad wrap mode");
+      return 0;
+   }
 }
 
 
 /* Power of two image sizes only */
-#define COMPUTE_LINEAR_REPEAT_TEXEL_LOCATION(S, U, SIZE, I0, I1)	\
-{									\
-   U = S * SIZE - 0.5F;							\
-   I0 = IFLOOR(U) & (SIZE - 1);						\
-   I1 = (I0 + 1) & (SIZE - 1);						\
+static INLINE void
+linear_repeat_texel_location(GLuint size, GLfloat s,
+                             GLint *i0, GLint *i1, GLfloat *weight)
+{
+   GLfloat u = s * size - 0.5F;
+   *i0 = IFLOOR(u) & (size - 1);
+   *i1 = (*i0 + 1) & (size - 1);
+   *weight = FRAC(u);
 }
 
 
@@ -516,17 +540,6 @@ nearest_mipmap_level(const struct gl_texture_object *tObj, GLfloat lambda)
 
 
 /*
- * Note, the FRAC macro has to work perfectly.  Otherwise you'll sometimes
- * see 1-pixel bands of improperly weighted linear-filtered textures.
- * The tests/texwrap.c demo is a good test.
- * Also note, FRAC(x) doesn't truly return the fractional part of x for x < 0.
- * Instead, if x < 0 then FRAC(x) = 1 - true_frac(x).
- */
-#define FRAC(f)  ((f) - IFLOOR(f))
-
-
-
-/*
  * Bitflags for texture border color sampling.
  */
 #define I0BIT   1
@@ -538,7 +551,7 @@ nearest_mipmap_level(const struct gl_texture_object *tObj, GLfloat lambda)
 
 
 
-/*
+/**
  * The lambda[] array values are always monotonic.  Either the whole span
  * will be minified, magnified, or split between the two.  This function
  * determines the subranges in [0, n-1] that are to be minified or magnified.
@@ -651,10 +664,10 @@ compute_min_mag_ranges(const struct gl_texture_object *tObj,
 /*                    1-D Texture Sampling Functions                  */
 /**********************************************************************/
 
-/*
+/**
  * Return the texture sample for coordinate (s) using GL_NEAREST filter.
  */
-static void
+static INLINE void
 sample_1d_nearest(GLcontext *ctx,
                   const struct gl_texture_object *tObj,
                   const struct gl_texture_image *img,
@@ -662,7 +675,7 @@ sample_1d_nearest(GLcontext *ctx,
 {
    const GLint width = img->Width2;  /* without border, power of two */
    GLint i;
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoord[0], width, i);
+   i = nearest_texel_location(tObj->WrapS, img, width, texcoord[0]);
    /* skip over the border, if any */
    i += img->Border;
    if (i < 0 || i >= (GLint) img->Width) {
@@ -675,10 +688,10 @@ sample_1d_nearest(GLcontext *ctx,
 }
 
 
-/*
+/**
  * Return the texture sample for coordinate (s) using GL_LINEAR filter.
  */
-static void
+static INLINE void
 sample_1d_linear(GLcontext *ctx,
                  const struct gl_texture_object *tObj,
                  const struct gl_texture_image *img,
@@ -686,12 +699,11 @@ sample_1d_linear(GLcontext *ctx,
 {
    const GLint width = img->Width2;
    GLint i0, i1;
-   GLfloat u;
    GLbitfield useBorderColor = 0x0;
    GLfloat a;
    GLchan t0[4], t1[4];  /* texels */
 
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoord[0], u, width, i0, i1);
+   linear_texel_locations(tObj->WrapS, img, width, texcoord[0], &i0, &i1, &a);
 
    if (img->Border) {
       i0 += img->Border;
@@ -716,7 +728,6 @@ sample_1d_linear(GLcontext *ctx,
       img->FetchTexelc(img, i1, 0, 0, t1);
    }
 
-   a = FRAC(u);
    lerp_rgba(rgba, a, t0, t1);
 }
 
@@ -776,7 +787,6 @@ sample_1d_nearest_mipmap_linear(GLcontext *ctx,
 }
 
 
-
 static void
 sample_1d_linear_mipmap_linear(GLcontext *ctx,
                                const struct gl_texture_object *tObj,
@@ -802,7 +812,7 @@ sample_1d_linear_mipmap_linear(GLcontext *ctx,
 }
 
 
-
+/** Sample 1D texture, nearest filtering for both min/magnification */
 static void
 sample_nearest_1d( GLcontext *ctx,
                    const struct gl_texture_object *tObj, GLuint n,
@@ -812,13 +822,13 @@ sample_nearest_1d( GLcontext *ctx,
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_1d_nearest(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-
+/** Sample 1D texture, linear filtering for both min/magnification */
 static void
 sample_linear_1d( GLcontext *ctx,
                   const struct gl_texture_object *tObj, GLuint n,
@@ -828,17 +838,13 @@ sample_linear_1d( GLcontext *ctx,
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_1d_linear(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-/*
- * Given an (s) texture coordinate and lambda (level of detail) value,
- * return a texture sample.
- *
- */
+/** Sample 1D texture, using lambda to choose between min/magnification */
 static void
 sample_lambda_1d( GLcontext *ctx,
                   const struct gl_texture_object *tObj, GLuint n,
@@ -915,7 +921,7 @@ sample_lambda_1d( GLcontext *ctx,
 /**********************************************************************/
 
 
-/*
+/**
  * Return the texture sample for coordinate (s,t) using GL_NEAREST filter.
  */
 static INLINE void
@@ -930,8 +936,8 @@ sample_2d_nearest(GLcontext *ctx,
    GLint i, j;
    (void) ctx;
 
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoord[0], width,  i);
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapT, texcoord[1], height, j);
+   i = nearest_texel_location(tObj->WrapS, img, width, texcoord[0]);
+   j = nearest_texel_location(tObj->WrapT, img, height, texcoord[1]);
 
    /* skip over the border, if any */
    i += img->Border;
@@ -947,7 +953,6 @@ sample_2d_nearest(GLcontext *ctx,
 }
 
 
-
 /**
  * Return the texture sample for coordinate (s,t) using GL_LINEAR filter.
  * New sampling code contributed by Lynn Quam <quam@ai.sri.com>.
@@ -963,12 +968,11 @@ sample_2d_linear(GLcontext *ctx,
    const GLint height = img->Height2;
    GLint i0, j0, i1, j1;
    GLbitfield useBorderColor = 0x0;
-   GLfloat u, v;
    GLfloat a, b;
    GLchan t00[4], t10[4], t01[4], t11[4]; /* sampled texel colors */
 
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoord[0], u, width,  i0, i1);
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapT, texcoord[1], v, height, j0, j1);
+   linear_texel_locations(tObj->WrapS, img, width, texcoord[0],  &i0, &i1, &a);
+   linear_texel_locations(tObj->WrapT, img, height, texcoord[1], &j0, &j1, &b);
 
    if (img->Border) {
       i0 += img->Border;
@@ -1009,13 +1013,11 @@ sample_2d_linear(GLcontext *ctx,
       img->FetchTexelc(img, i1, j1, 0, t11);
    }
 
-   a = FRAC(u);
-   b = FRAC(v);
    lerp_rgba_2d(rgba, a, b, t00, t10, t01, t11);
 }
 
 
-/*
+/**
  * As above, but we know WRAP_S == REPEAT and WRAP_T == REPEAT.
  * We don't have to worry about the texture border.
  */
@@ -1029,8 +1031,7 @@ sample_2d_linear_repeat(GLcontext *ctx,
    const GLint width = img->Width2;
    const GLint height = img->Height2;
    GLint i0, j0, i1, j1;
-   GLfloat u, v;
-   GLfloat a, b;
+   GLfloat wi, wj;
    GLchan t00[4], t10[4], t01[4], t11[4]; /* sampled texel colors */
 
    (void) ctx;
@@ -1041,21 +1042,18 @@ sample_2d_linear_repeat(GLcontext *ctx,
    ASSERT(img->TexFormat->BaseFormat != GL_COLOR_INDEX);
    ASSERT(img->_IsPowerOfTwo);
 
-   COMPUTE_LINEAR_REPEAT_TEXEL_LOCATION(texcoord[0], u, width,  i0, i1);
-   COMPUTE_LINEAR_REPEAT_TEXEL_LOCATION(texcoord[1], v, height, j0, j1);
+   linear_repeat_texel_location(width,  texcoord[0], &i0, &i1, &wi);
+   linear_repeat_texel_location(height, texcoord[1], &j0, &j1, &wj);
 
    img->FetchTexelc(img, i0, j0, 0, t00);
    img->FetchTexelc(img, i1, j0, 0, t10);
    img->FetchTexelc(img, i0, j1, 0, t01);
    img->FetchTexelc(img, i1, j1, 0, t11);
 
-   a = FRAC(u);
-   b = FRAC(v);
-   lerp_rgba_2d(rgba, a, b, t00, t10, t01, t11);
+   lerp_rgba_2d(rgba, wi, wj, t00, t10, t01, t11);
 }
 
 
-
 static void
 sample_2d_nearest_mipmap_nearest(GLcontext *ctx,
                                  const struct gl_texture_object *tObj,
@@ -1070,7 +1068,6 @@ sample_2d_nearest_mipmap_nearest(GLcontext *ctx,
 }
 
 
-
 static void
 sample_2d_linear_mipmap_nearest(GLcontext *ctx,
                                 const struct gl_texture_object *tObj,
@@ -1086,7 +1083,6 @@ sample_2d_linear_mipmap_nearest(GLcontext *ctx,
 }
 
 
-
 static void
 sample_2d_nearest_mipmap_linear(GLcontext *ctx,
                                 const struct gl_texture_object *tObj,
@@ -1112,8 +1108,6 @@ sample_2d_nearest_mipmap_linear(GLcontext *ctx,
 }
 
 
-
-/* Trilinear filtering */
 static void
 sample_2d_linear_mipmap_linear( GLcontext *ctx,
                                 const struct gl_texture_object *tObj,
@@ -1140,10 +1134,10 @@ sample_2d_linear_mipmap_linear( GLcontext *ctx,
 
 
 static void
-sample_2d_linear_mipmap_linear_repeat( GLcontext *ctx,
-                                       const struct gl_texture_object *tObj,
-                                       GLuint n, const GLfloat texcoord[][4],
-                                       const GLfloat lambda[], GLchan rgba[][4] )
+sample_2d_linear_mipmap_linear_repeat(GLcontext *ctx,
+                                      const struct gl_texture_object *tObj,
+                                      GLuint n, const GLfloat texcoord[][4],
+                                      const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    ASSERT(lambda != NULL);
@@ -1158,35 +1152,38 @@ sample_2d_linear_mipmap_linear_repeat( GLcontext *ctx,
       else {
          GLchan t0[4], t1[4];  /* texels */
          const GLfloat f = FRAC(lambda[i]);
-         sample_2d_linear_repeat(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
-         sample_2d_linear_repeat(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
+         sample_2d_linear_repeat(ctx, tObj, tObj->Image[0][level  ],
+                                 texcoord[i], t0);
+         sample_2d_linear_repeat(ctx, tObj, tObj->Image[0][level+1],
+                                 texcoord[i], t1);
          lerp_rgba(rgba[i], f, t0, t1);
       }
    }
 }
 
 
+/** Sample 2D texture, nearest filtering for both min/magnification */
 static void
-sample_nearest_2d( GLcontext *ctx,
-                   const struct gl_texture_object *tObj, GLuint n,
-                   const GLfloat texcoords[][4],
-                   const GLfloat lambda[], GLchan rgba[][4] )
+sample_nearest_2d(GLcontext *ctx,
+                  const struct gl_texture_object *tObj, GLuint n,
+                  const GLfloat texcoords[][4],
+                  const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_2d_nearest(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-
+/** Sample 2D texture, linear filtering for both min/magnification */
 static void
-sample_linear_2d( GLcontext *ctx,
-                  const struct gl_texture_object *tObj, GLuint n,
-                  const GLfloat texcoords[][4],
-                  const GLfloat lambda[], GLchan rgba[][4] )
+sample_linear_2d(GLcontext *ctx,
+                 const struct gl_texture_object *tObj, GLuint n,
+                 const GLfloat texcoords[][4],
+                 const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
@@ -1195,19 +1192,19 @@ sample_linear_2d( GLcontext *ctx,
        tObj->WrapT == GL_REPEAT &&
        image->_IsPowerOfTwo &&
        image->Border == 0) {
-      for (i=0;i<n;i++) {
+      for (i = 0; i < n; i++) {
          sample_2d_linear_repeat(ctx, tObj, image, texcoords[i], rgba[i]);
       }
    }
    else {
-      for (i=0;i<n;i++) {
+      for (i = 0; i < n; i++) {
          sample_2d_linear(ctx, tObj, image, texcoords[i], rgba[i]);
       }
    }
 }
 
 
-/*
+/**
  * Optimized 2-D texture sampling:
  *    S and T wrap mode == GL_REPEAT
  *    GL_NEAREST min/mag filter
@@ -1216,10 +1213,10 @@ sample_linear_2d( GLcontext *ctx,
  *    Format = GL_RGB
  */
 static void
-opt_sample_rgb_2d( GLcontext *ctx,
-                   const struct gl_texture_object *tObj,
-                   GLuint n, const GLfloat texcoords[][4],
-                   const GLfloat lambda[], GLchan rgba[][4] )
+opt_sample_rgb_2d(GLcontext *ctx,
+                  const struct gl_texture_object *tObj,
+                  GLuint n, const GLfloat texcoords[][4],
+                  const GLfloat lambda[], GLchan rgba[][4])
 {
    const struct gl_texture_image *img = tObj->Image[0][tObj->BaseLevel];
    const GLfloat width = (GLfloat) img->Width;
@@ -1248,7 +1245,7 @@ opt_sample_rgb_2d( GLcontext *ctx,
 }
 
 
-/*
+/**
  * Optimized 2-D texture sampling:
  *    S and T wrap mode == GL_REPEAT
  *    GL_NEAREST min/mag filter
@@ -1257,10 +1254,10 @@ opt_sample_rgb_2d( GLcontext *ctx,
  *    Format = GL_RGBA
  */
 static void
-opt_sample_rgba_2d( GLcontext *ctx,
-                    const struct gl_texture_object *tObj,
-                    GLuint n, const GLfloat texcoords[][4],
-                    const GLfloat lambda[], GLchan rgba[][4] )
+opt_sample_rgba_2d(GLcontext *ctx,
+                   const struct gl_texture_object *tObj,
+                   GLuint n, const GLfloat texcoords[][4],
+                   const GLfloat lambda[], GLchan rgba[][4])
 {
    const struct gl_texture_image *img = tObj->Image[0][tObj->BaseLevel];
    const GLfloat width = (GLfloat) img->Width;
@@ -1287,15 +1284,12 @@ opt_sample_rgba_2d( GLcontext *ctx,
 }
 
 
-/*
- * Given an array of texture coordinate and lambda (level of detail)
- * values, return an array of texture sample.
- */
+/** Sample 2D texture, using lambda to choose between min/magnification */
 static void
-sample_lambda_2d( GLcontext *ctx,
-                  const struct gl_texture_object *tObj,
-                  GLuint n, const GLfloat texcoords[][4],
-                  const GLfloat lambda[], GLchan rgba[][4] )
+sample_lambda_2d(GLcontext *ctx,
+                 const struct gl_texture_object *tObj,
+                 GLuint n, const GLfloat texcoords[][4],
+                 const GLfloat lambda[], GLchan rgba[][4])
 {
    const struct gl_texture_image *tImg = tObj->Image[0][tObj->BaseLevel];
    GLuint minStart, minEnd;  /* texels with minification */
@@ -1409,10 +1403,10 @@ sample_lambda_2d( GLcontext *ctx,
 /*                    3-D Texture Sampling Functions                  */
 /**********************************************************************/
 
-/*
+/**
  * Return the texture sample for coordinate (s,t,r) using GL_NEAREST filter.
  */
-static void
+static INLINE void
 sample_3d_nearest(GLcontext *ctx,
                   const struct gl_texture_object *tObj,
                   const struct gl_texture_image *img,
@@ -1425,9 +1419,9 @@ sample_3d_nearest(GLcontext *ctx,
    GLint i, j, k;
    (void) ctx;
 
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoord[0], width,  i);
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapT, texcoord[1], height, j);
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapR, texcoord[2], depth,  k);
+   i = nearest_texel_location(tObj->WrapS, img, width, texcoord[0]);
+   j = nearest_texel_location(tObj->WrapT, img, height, texcoord[1]);
+   k = nearest_texel_location(tObj->WrapR, img, depth, texcoord[2]);
 
    if (i < 0 || i >= (GLint) img->Width ||
        j < 0 || j >= (GLint) img->Height ||
@@ -1441,8 +1435,7 @@ sample_3d_nearest(GLcontext *ctx,
 }
 
 
-
-/*
+/**
  * Return the texture sample for coordinate (s,t,r) using GL_LINEAR filter.
  */
 static void
@@ -1457,14 +1450,13 @@ sample_3d_linear(GLcontext *ctx,
    const GLint depth = img->Depth2;
    GLint i0, j0, k0, i1, j1, k1;
    GLbitfield useBorderColor = 0x0;
-   GLfloat u, v, w;
    GLfloat a, b, c;
    GLchan t000[4], t010[4], t001[4], t011[4];
    GLchan t100[4], t110[4], t101[4], t111[4];
 
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoord[0], u, width,  i0, i1);
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapT, texcoord[1], v, height, j0, j1);
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapR, texcoord[2], w, depth,  k0, k1);
+   linear_texel_locations(tObj->WrapS, img, width, texcoord[0],  &i0, &i1, &a);
+   linear_texel_locations(tObj->WrapT, img, height, texcoord[1], &j0, &j1, &b);
+   linear_texel_locations(tObj->WrapR, img, depth, texcoord[2],  &k0, &k1, &c);
 
    if (img->Border) {
       i0 += img->Border;
@@ -1536,14 +1528,10 @@ sample_3d_linear(GLcontext *ctx,
    }
 
    /* trilinear interpolation of samples */
-   a = FRAC(u);
-   b = FRAC(v);
-   c = FRAC(w);
    lerp_rgba_3d(rgba, a, b, c, t000, t100, t010, t110, t001, t101, t011, t111);
 }
 
 
-
 static void
 sample_3d_nearest_mipmap_nearest(GLcontext *ctx,
                                  const struct gl_texture_object *tObj,
@@ -1623,6 +1611,7 @@ sample_3d_linear_mipmap_linear(GLcontext *ctx,
 }
 
 
+/** Sample 3D texture, nearest filtering for both min/magnification */
 static void
 sample_nearest_3d(GLcontext *ctx,
                   const struct gl_texture_object *tObj, GLuint n,
@@ -1632,37 +1621,34 @@ sample_nearest_3d(GLcontext *ctx,
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_3d_nearest(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-
+/** Sample 3D texture, linear filtering for both min/magnification */
 static void
-sample_linear_3d( GLcontext *ctx,
-                  const struct gl_texture_object *tObj, GLuint n,
-                  const GLfloat texcoords[][4],
-		  const GLfloat lambda[], GLchan rgba[][4] )
+sample_linear_3d(GLcontext *ctx,
+                 const struct gl_texture_object *tObj, GLuint n,
+                 const GLfloat texcoords[][4],
+		 const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_3d_linear(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-/*
- * Given an (s,t,r) texture coordinate and lambda (level of detail) value,
- * return a texture sample.
- */
+/** Sample 3D texture, using lambda to choose between min/magnification */
 static void
-sample_lambda_3d( GLcontext *ctx,
-                  const struct gl_texture_object *tObj, GLuint n,
-                  const GLfloat texcoords[][4], const GLfloat lambda[],
-                  GLchan rgba[][4] )
+sample_lambda_3d(GLcontext *ctx,
+                 const struct gl_texture_object *tObj, GLuint n,
+                 const GLfloat texcoords[][4], const GLfloat lambda[],
+                 GLchan rgba[][4])
 {
    GLuint minStart, minEnd;  /* texels with minification */
    GLuint magStart, magEnd;  /* texels with magnification */
@@ -1951,11 +1937,12 @@ sample_cube_linear_mipmap_linear(GLcontext *ctx,
 }
 
 
+/** Sample cube texture, using lambda to choose between min/magnification */
 static void
-sample_lambda_cube( GLcontext *ctx,
-		    const struct gl_texture_object *tObj, GLuint n,
-		    const GLfloat texcoords[][4], const GLfloat lambda[],
-		    GLchan rgba[][4])
+sample_lambda_cube(GLcontext *ctx,
+		   const struct gl_texture_object *tObj, GLuint n,
+		   const GLfloat texcoords[][4], const GLfloat lambda[],
+		   GLchan rgba[][4])
 {
    GLuint minStart, minEnd;  /* texels with minification */
    GLuint magStart, magEnd;  /* texels with magnification */
@@ -2031,50 +2018,56 @@ sample_lambda_cube( GLcontext *ctx,
 static INLINE GLint
 clamp_rect_coord_nearest(GLenum wrapMode, GLfloat coord, GLint max)
 {
-   if (wrapMode == GL_CLAMP) {
+   switch (wrapMode) {
+   case GL_CLAMP:
       return IFLOOR( CLAMP(coord, 0.0F, max - 1) );
-   }
-   else if (wrapMode == GL_CLAMP_TO_EDGE) {
+   case GL_CLAMP_TO_EDGE:
       return IFLOOR( CLAMP(coord, 0.5F, max - 0.5F) );
-   }
-   else {
+   case GL_CLAMP_TO_BORDER:
       return IFLOOR( CLAMP(coord, -0.5F, max + 0.5F) );
+   default:
+      _mesa_problem(NULL, "bad wrapMode in clamp_rect_coord_nearest");
+      return 0;
    }
 }
 
 
-/*
+/**
  * As above, but GL_LINEAR filtering.
  */
 static INLINE void
 clamp_rect_coord_linear(GLenum wrapMode, GLfloat coord, GLint max,
-                        GLint *i0out, GLint *i1out)
+                        GLint *i0out, GLint *i1out, GLfloat *weight)
 {
    GLfloat fcol;
    GLint i0, i1;
-   if (wrapMode == GL_CLAMP) {
+   switch (wrapMode) {
+   case GL_CLAMP:
       /* Not exactly what the spec says, but it matches NVIDIA output */
       fcol = CLAMP(coord - 0.5F, 0.0, max-1);
       i0 = IFLOOR(fcol);
       i1 = i0 + 1;
-   }
-   else if (wrapMode == GL_CLAMP_TO_EDGE) {
+      break;
+   case GL_CLAMP_TO_EDGE:
       fcol = CLAMP(coord, 0.5F, max - 0.5F);
       fcol -= 0.5F;
       i0 = IFLOOR(fcol);
       i1 = i0 + 1;
       if (i1 > max - 1)
          i1 = max - 1;
-   }
-   else {
-      ASSERT(wrapMode == GL_CLAMP_TO_BORDER);
+      break;
+   case GL_CLAMP_TO_BORDER:
       fcol = CLAMP(coord, -0.5F, max + 0.5F);
       fcol -= 0.5F;
       i0 = IFLOOR(fcol);
       i1 = i0 + 1;
+   default:
+      _mesa_problem(NULL, "bad wrapMode in clamp_rect_coord_linear");
+      i0 = i1 = 0;
    }
    *i0out = i0;
    *i1out = i1;
+   *weight = FRAC(fcol);
 }
 
 
@@ -2085,10 +2078,8 @@ sample_nearest_rect(GLcontext *ctx,
                     GLchan rgba[][4])
 {
    const struct gl_texture_image *img = tObj->Image[0][0];
-   const GLfloat width = (GLfloat) img->Width;
-   const GLfloat height = (GLfloat) img->Height;
-   const GLint width_minus_1 = img->Width - 1;
-   const GLint height_minus_1 = img->Height - 1;
+   const GLint width = img->Width;
+   const GLint height = img->Height;
    GLuint i;
 
    (void) ctx;
@@ -2106,7 +2097,7 @@ sample_nearest_rect(GLcontext *ctx,
       GLint row, col;
       col = clamp_rect_coord_nearest(tObj->WrapS, texcoords[i][0], width);
       row = clamp_rect_coord_nearest(tObj->WrapT, texcoords[i][1], height);
-      if (col < 0 || col > width_minus_1 || row < 0 || row > height_minus_1)
+      if (col < 0 || col >= width || row < 0 || row >= height)
          COPY_CHAN4(rgba[i], tObj->_BorderChan);
       else
          img->FetchTexelc(img, col, row, 0, rgba[i]);
@@ -2121,10 +2112,8 @@ sample_linear_rect(GLcontext *ctx,
 		   const GLfloat lambda[], GLchan rgba[][4])
 {
    const struct gl_texture_image *img = tObj->Image[0][0];
-   const GLfloat width = (GLfloat) img->Width;
-   const GLfloat height = (GLfloat) img->Height;
-   const GLint width_minus_1 = img->Width - 1;
-   const GLint height_minus_1 = img->Height - 1;
+   const GLint width = img->Width;
+   const GLint height = img->Height;
    GLuint i;
 
    (void) ctx;
@@ -2138,64 +2127,22 @@ sample_linear_rect(GLcontext *ctx,
           tObj->WrapT == GL_CLAMP_TO_BORDER);
    ASSERT(img->TexFormat->BaseFormat != GL_COLOR_INDEX);
 
-   /* XXX lots of opportunity for optimization in this loop */
    for (i = 0; i < n; i++) {
-      GLfloat frow, fcol;
       GLint i0, j0, i1, j1;
       GLchan t00[4], t01[4], t10[4], t11[4];
       GLfloat a, b;
       GLbitfield useBorderColor = 0x0;
 
-      /* NOTE: we DO NOT use [0, 1] texture coordinates! */
-      if (tObj->WrapS == GL_CLAMP) {
-         /* Not exactly what the spec says, but it matches NVIDIA output */
-         fcol = CLAMP(texcoords[i][0] - 0.5F, 0.0, width_minus_1);
-         i0 = IFLOOR(fcol);
-         i1 = i0 + 1;
-      }
-      else if (tObj->WrapS == GL_CLAMP_TO_EDGE) {
-         fcol = CLAMP(texcoords[i][0], 0.5F, width - 0.5F);
-         fcol -= 0.5F;
-         i0 = IFLOOR(fcol);
-         i1 = i0 + 1;
-         if (i1 > width_minus_1)
-            i1 = width_minus_1;
-      }
-      else {
-         ASSERT(tObj->WrapS == GL_CLAMP_TO_BORDER);
-         fcol = CLAMP(texcoords[i][0], -0.5F, width + 0.5F);
-         fcol -= 0.5F;
-         i0 = IFLOOR(fcol);
-         i1 = i0 + 1;
-      }
-
-      if (tObj->WrapT == GL_CLAMP) {
-         /* Not exactly what the spec says, but it matches NVIDIA output */
-         frow = CLAMP(texcoords[i][1] - 0.5F, 0.0, width_minus_1);
-         j0 = IFLOOR(frow);
-         j1 = j0 + 1;
-      }
-      else if (tObj->WrapT == GL_CLAMP_TO_EDGE) {
-         frow = CLAMP(texcoords[i][1], 0.5F, height - 0.5F);
-         frow -= 0.5F;
-         j0 = IFLOOR(frow);
-         j1 = j0 + 1;
-         if (j1 > height_minus_1)
-            j1 = height_minus_1;
-      }
-      else {
-         ASSERT(tObj->WrapT == GL_CLAMP_TO_BORDER);
-         frow = CLAMP(texcoords[i][1], -0.5F, height + 0.5F);
-         frow -= 0.5F;
-         j0 = IFLOOR(frow);
-         j1 = j0 + 1;
-      }
+      clamp_rect_coord_linear(tObj->WrapS, texcoords[i][0], width,
+                              &i0, &i1, &a);
+      clamp_rect_coord_linear(tObj->WrapT, texcoords[i][1], height,
+                              &j0, &j1, &b);
 
       /* compute integer rows/columns */
-      if (i0 < 0 || i0 > width_minus_1)   useBorderColor |= I0BIT;
-      if (i1 < 0 || i1 > width_minus_1)   useBorderColor |= I1BIT;
-      if (j0 < 0 || j0 > height_minus_1)  useBorderColor |= J0BIT;
-      if (j1 < 0 || j1 > height_minus_1)  useBorderColor |= J1BIT;
+      if (i0 < 0 || i0 >= width)   useBorderColor |= I0BIT;
+      if (i1 < 0 || i1 >= width)   useBorderColor |= I1BIT;
+      if (j0 < 0 || j0 >= height)  useBorderColor |= J0BIT;
+      if (j1 < 0 || j1 >= height)  useBorderColor |= J1BIT;
 
       /* get four texel samples */
       if (useBorderColor & (I0BIT | J0BIT))
@@ -2218,20 +2165,17 @@ sample_linear_rect(GLcontext *ctx,
       else
          img->FetchTexelc(img, i1, j1, 0, t11);
 
-      /* compute interpolants */
-      a = FRAC(fcol);
-      b = FRAC(frow);
-
       lerp_rgba_2d(rgba[i], a, b, t00, t10, t01, t11);
    }
 }
 
 
+/** Sample Rect texture, using lambda to choose between min/magnification */
 static void
-sample_lambda_rect( GLcontext *ctx,
-		    const struct gl_texture_object *tObj, GLuint n,
-		    const GLfloat texcoords[][4], const GLfloat lambda[],
-		    GLchan rgba[][4])
+sample_lambda_rect(GLcontext *ctx,
+		   const struct gl_texture_object *tObj, GLuint n,
+		   const GLfloat texcoords[][4], const GLfloat lambda[],
+		   GLchan rgba[][4])
 {
    GLuint minStart, minEnd, magStart, magEnd;
 
@@ -2243,22 +2187,22 @@ sample_lambda_rect( GLcontext *ctx,
 
    if (minStart < minEnd) {
       if (tObj->MinFilter == GL_NEAREST) {
-         sample_nearest_rect( ctx, tObj, minEnd - minStart,
-                              texcoords + minStart, NULL, rgba + minStart);
+         sample_nearest_rect(ctx, tObj, minEnd - minStart,
+                             texcoords + minStart, NULL, rgba + minStart);
       }
       else {
-         sample_linear_rect( ctx, tObj, minEnd - minStart,
-                             texcoords + minStart, NULL, rgba + minStart);
+         sample_linear_rect(ctx, tObj, minEnd - minStart,
+                            texcoords + minStart, NULL, rgba + minStart);
       }
    }
    if (magStart < magEnd) {
       if (tObj->MagFilter == GL_NEAREST) {
-         sample_nearest_rect( ctx, tObj, magEnd - magStart,
-                              texcoords + magStart, NULL, rgba + magStart);
+         sample_nearest_rect(ctx, tObj, magEnd - magStart,
+                             texcoords + magStart, NULL, rgba + magStart);
       }
       else {
-         sample_linear_rect( ctx, tObj, magEnd - magStart,
-                             texcoords + magStart, NULL, rgba + magStart);
+         sample_linear_rect(ctx, tObj, magEnd - magStart,
+                            texcoords + magStart, NULL, rgba + magStart);
       }
    }
 }
@@ -2269,7 +2213,7 @@ sample_lambda_rect( GLcontext *ctx,
 /*                2D Texture Array Sampling Functions                 */
 /**********************************************************************/
 
-/*
+/**
  * Return the texture sample for coordinate (s,t,r) using GL_NEAREST filter.
  */
 static void
@@ -2286,8 +2230,8 @@ sample_2d_array_nearest(GLcontext *ctx,
    GLint array;
    (void) ctx;
 
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoord[0], width,  i);
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapT, texcoord[1], height, j);
+   i = nearest_texel_location(tObj->WrapS, img, width, texcoord[0]);
+   j = nearest_texel_location(tObj->WrapT, img, height, texcoord[1]);
    array = clamp_rect_coord_nearest(tObj->WrapR, texcoord[2], depth);
 
    if (i < 0 || i >= (GLint) img->Width ||
@@ -2302,8 +2246,7 @@ sample_2d_array_nearest(GLcontext *ctx,
 }
 
 
-
-/*
+/**
  * Return the texture sample for coordinate (s,t,r) using GL_LINEAR filter.
  */
 static void
@@ -2319,12 +2262,11 @@ sample_2d_array_linear(GLcontext *ctx,
    GLint i0, j0, i1, j1;
    GLint array;
    GLbitfield useBorderColor = 0x0;
-   GLfloat u, v;
    GLfloat a, b;
    GLchan t00[4], t01[4], t10[4], t11[4];
 
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoord[0], u, width,  i0, i1);
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapT, texcoord[1], v, height, j0, j1);
+   linear_texel_locations(tObj->WrapS, img, width,  texcoord[0], &i0, &i1, &a);
+   linear_texel_locations(tObj->WrapT, img, height, texcoord[1], &j0, &j1, &b);
    array = clamp_rect_coord_nearest(tObj->WrapR, texcoord[2], depth);
 
    if (array < 0 || array >= depth) {
@@ -2372,19 +2314,16 @@ sample_2d_array_linear(GLcontext *ctx,
       }
       
       /* trilinear interpolation of samples */
-      a = FRAC(u);
-      b = FRAC(v);
       lerp_rgba_2d(rgba, a, b, t00, t10, t01, t11);
    }
 }
 
 
-
 static void
 sample_2d_array_nearest_mipmap_nearest(GLcontext *ctx,
                                        const struct gl_texture_object *tObj,
                                        GLuint n, const GLfloat texcoord[][4],
-                                       const GLfloat lambda[], GLchan rgba[][4] )
+                                       const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    for (i = 0; i < n; i++) {
@@ -2428,8 +2367,10 @@ sample_2d_array_nearest_mipmap_linear(GLcontext *ctx,
       else {
          GLchan t0[4], t1[4];  /* texels */
          const GLfloat f = FRAC(lambda[i]);
-         sample_2d_array_nearest(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
-         sample_2d_array_nearest(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
+         sample_2d_array_nearest(ctx, tObj, tObj->Image[0][level  ],
+                                 texcoord[i], t0);
+         sample_2d_array_nearest(ctx, tObj, tObj->Image[0][level+1],
+                                 texcoord[i], t1);
          lerp_rgba(rgba[i], f, t0, t1);
       }
    }
@@ -2438,9 +2379,9 @@ sample_2d_array_nearest_mipmap_linear(GLcontext *ctx,
 
 static void
 sample_2d_array_linear_mipmap_linear(GLcontext *ctx,
-                               const struct gl_texture_object *tObj,
-                               GLuint n, const GLfloat texcoord[][4],
-                               const GLfloat lambda[], GLchan rgba[][4])
+                                     const struct gl_texture_object *tObj,
+                                     GLuint n, const GLfloat texcoord[][4],
+                                     const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    ASSERT(lambda != NULL);
@@ -2453,30 +2394,34 @@ sample_2d_array_linear_mipmap_linear(GLcontext *ctx,
       else {
          GLchan t0[4], t1[4];  /* texels */
          const GLfloat f = FRAC(lambda[i]);
-         sample_2d_array_linear(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
-         sample_2d_array_linear(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
+         sample_2d_array_linear(ctx, tObj, tObj->Image[0][level  ],
+                                texcoord[i], t0);
+         sample_2d_array_linear(ctx, tObj, tObj->Image[0][level+1],
+                                texcoord[i], t1);
          lerp_rgba(rgba[i], f, t0, t1);
       }
    }
 }
 
 
+/** Sample 2D Array texture, nearest filtering for both min/magnification */
 static void
 sample_nearest_2d_array(GLcontext *ctx,
-                  const struct gl_texture_object *tObj, GLuint n,
-                  const GLfloat texcoords[][4], const GLfloat lambda[],
-                  GLchan rgba[][4])
+                        const struct gl_texture_object *tObj, GLuint n,
+                        const GLfloat texcoords[][4], const GLfloat lambda[],
+                        GLchan rgba[][4])
 {
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_2d_array_nearest(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
 
+/** Sample 2D Array texture, linear filtering for both min/magnification */
 static void
 sample_linear_2d_array(GLcontext *ctx,
                        const struct gl_texture_object *tObj, GLuint n,
@@ -2486,16 +2431,13 @@ sample_linear_2d_array(GLcontext *ctx,
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_2d_array_linear(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-/*
- * Given an (s,t,r) texture coordinate and lambda (level of detail) value,
- * return a texture sample.
- */
+/** Sample 2D Array texture, using lambda to choose between min/magnification */
 static void
 sample_lambda_2d_array(GLcontext *ctx,
                        const struct gl_texture_object *tObj, GLuint n,
@@ -2525,8 +2467,10 @@ sample_lambda_2d_array(GLcontext *ctx,
                                    texcoords[i], rgba[i]);
          break;
       case GL_NEAREST_MIPMAP_NEAREST:
-         sample_2d_array_nearest_mipmap_nearest(ctx, tObj, m, texcoords + minStart,
-                                                lambda + minStart, rgba + minStart);
+         sample_2d_array_nearest_mipmap_nearest(ctx, tObj, m,
+                                                texcoords + minStart,
+                                                lambda + minStart,
+                                                rgba + minStart);
          break;
       case GL_LINEAR_MIPMAP_NEAREST:
          sample_2d_array_linear_mipmap_nearest(ctx, tObj, m, 
@@ -2535,8 +2479,10 @@ sample_lambda_2d_array(GLcontext *ctx,
                                                rgba + minStart);
          break;
       case GL_NEAREST_MIPMAP_LINEAR:
-         sample_2d_array_nearest_mipmap_linear(ctx, tObj, m, texcoords + minStart,
-                                               lambda + minStart, rgba + minStart);
+         sample_2d_array_nearest_mipmap_linear(ctx, tObj, m,
+                                               texcoords + minStart,
+                                               lambda + minStart,
+                                               rgba + minStart);
          break;
       case GL_LINEAR_MIPMAP_LINEAR:
          sample_2d_array_linear_mipmap_linear(ctx, tObj, m, 
@@ -2577,7 +2523,7 @@ sample_lambda_2d_array(GLcontext *ctx,
 /*                1D Texture Array Sampling Functions                 */
 /**********************************************************************/
 
-/*
+/**
  * Return the texture sample for coordinate (s,t,r) using GL_NEAREST filter.
  */
 static void
@@ -2593,7 +2539,7 @@ sample_1d_array_nearest(GLcontext *ctx,
    GLint array;
    (void) ctx;
 
-   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoord[0], width,  i);
+   i = nearest_texel_location(tObj->WrapS, img, width, texcoord[0]);
    array = clamp_rect_coord_nearest(tObj->WrapT, texcoord[1], height);
 
    if (i < 0 || i >= (GLint) img->Width ||
@@ -2607,8 +2553,7 @@ sample_1d_array_nearest(GLcontext *ctx,
 }
 
 
-
-/*
+/**
  * Return the texture sample for coordinate (s,t,r) using GL_LINEAR filter.
  */
 static void
@@ -2623,11 +2568,10 @@ sample_1d_array_linear(GLcontext *ctx,
    GLint i0, i1;
    GLint array;
    GLbitfield useBorderColor = 0x0;
-   GLfloat u;
    GLfloat a;
    GLchan t0[4], t1[4];
 
-   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoord[0], u, width,  i0, i1);
+   linear_texel_locations(tObj->WrapS, img, width, texcoord[0], &i0, &i1, &a);
    array = clamp_rect_coord_nearest(tObj->WrapT, texcoord[1], height);
 
    if (img->Border) {
@@ -2657,17 +2601,15 @@ sample_1d_array_linear(GLcontext *ctx,
    }
 
    /* bilinear interpolation of samples */
-   a = FRAC(u);
    lerp_rgba(rgba, a, t0, t1);
 }
 
 
-
 static void
 sample_1d_array_nearest_mipmap_nearest(GLcontext *ctx,
                                        const struct gl_texture_object *tObj,
                                        GLuint n, const GLfloat texcoord[][4],
-                                       const GLfloat lambda[], GLchan rgba[][4] )
+                                       const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    for (i = 0; i < n; i++) {
@@ -2721,9 +2663,9 @@ sample_1d_array_nearest_mipmap_linear(GLcontext *ctx,
 
 static void
 sample_1d_array_linear_mipmap_linear(GLcontext *ctx,
-                               const struct gl_texture_object *tObj,
-                               GLuint n, const GLfloat texcoord[][4],
-                               const GLfloat lambda[], GLchan rgba[][4])
+                                     const struct gl_texture_object *tObj,
+                                     GLuint n, const GLfloat texcoord[][4],
+                                     const GLfloat lambda[], GLchan rgba[][4])
 {
    GLuint i;
    ASSERT(lambda != NULL);
@@ -2744,22 +2686,23 @@ sample_1d_array_linear_mipmap_linear(GLcontext *ctx,
 }
 
 
+/** Sample 1D Array texture, nearest filtering for both min/magnification */
 static void
 sample_nearest_1d_array(GLcontext *ctx,
-                  const struct gl_texture_object *tObj, GLuint n,
-                  const GLfloat texcoords[][4], const GLfloat lambda[],
-                  GLchan rgba[][4])
+                        const struct gl_texture_object *tObj, GLuint n,
+                        const GLfloat texcoords[][4], const GLfloat lambda[],
+                        GLchan rgba[][4])
 {
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_1d_array_nearest(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-
+/** Sample 1D Array texture, linear filtering for both min/magnification */
 static void
 sample_linear_1d_array(GLcontext *ctx,
                        const struct gl_texture_object *tObj, GLuint n,
@@ -2769,16 +2712,13 @@ sample_linear_1d_array(GLcontext *ctx,
    GLuint i;
    struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
    (void) lambda;
-   for (i=0;i<n;i++) {
+   for (i = 0; i < n; i++) {
       sample_1d_array_linear(ctx, tObj, image, texcoords[i], rgba[i]);
    }
 }
 
 
-/*
- * Given an (s,t,r) texture coordinate and lambda (level of detail) value,
- * return a texture sample.
- */
+/** Sample 1D Array texture, using lambda to choose between min/magnification */
 static void
 sample_lambda_1d_array(GLcontext *ctx,
                        const struct gl_texture_object *tObj, GLuint n,
@@ -2854,9 +2794,7 @@ sample_lambda_1d_array(GLcontext *ctx,
 }
 
 
-
-
-/*
+/**
  * Sample a shadow/depth texture.
  */
 static void
@@ -2906,31 +2844,32 @@ sample_depth_texture( GLcontext *ctx,
             break;
             
          case GL_TEXTURE_1D:
-            COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoords[i][0],
-                                           width, col);
+            col = nearest_texel_location(tObj->WrapS, img, width,
+                                         texcoords[i][0]);
             row = 0;
             slice = 0;
             break;
 
          case GL_TEXTURE_2D:
-            COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoords[i][0],
-                                           width, col);
-            COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapT, texcoords[i][1],
-                                           height, row);
+            col = nearest_texel_location(tObj->WrapS, img, width,
+                                         texcoords[i][0]);
+            row = nearest_texel_location(tObj->WrapT, img, height,
+                                         texcoords[i][1]);
             slice = 0;
             break;
 
          case GL_TEXTURE_1D_ARRAY_EXT:
-            COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoords[i][0],
-                                           width, col);
+            col = nearest_texel_location(tObj->WrapS, img, width,
+                                         texcoords[i][0]);
             row = clamp_rect_coord_nearest(tObj->WrapT, texcoords[i][1], height);
             slice = 0;
+            break;
 
          case GL_TEXTURE_2D_ARRAY_EXT:
-            COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoords[i][0],
-                                           width, col);
-            COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapT, texcoords[i][1],
-                                           height, row);
+            col = nearest_texel_location(tObj->WrapS, img, width,
+                                         texcoords[i][0]);
+            row = nearest_texel_location(tObj->WrapT, img, height,
+                                         texcoords[i][1]);
             slice = clamp_rect_coord_nearest(tObj->WrapR, texcoords[i][2], depth);
             break;
          }
@@ -3007,39 +2946,40 @@ sample_depth_texture( GLcontext *ctx,
          GLfloat depth00, depth01, depth10, depth11;
          GLint i0, i1, j0, j1;
          GLint slice;
-         GLfloat u, v;
+         GLfloat a, b;
          GLuint useBorderTexel;
 
          switch (tObj->Target) {
          case GL_TEXTURE_RECTANGLE_ARB:
             clamp_rect_coord_linear(tObj->WrapS, texcoords[i][0],
-                                    width, &i0, &i1);
+                                    width, &i0, &i1, &a);
             clamp_rect_coord_linear(tObj->WrapT, texcoords[i][1],
-                                    height, &j0, &j1);
+                                    height, &j0, &j1, &b);
             slice = 0;
             break;
 
          case GL_TEXTURE_1D:
          case GL_TEXTURE_2D:
-            COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoords[i][0],
-                                           u, width, i0, i1);
-            COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapT, texcoords[i][1],
-                                           v, height,j0, j1);
+            linear_texel_locations(tObj->WrapS, img, width,
+                                   texcoords[i][0], &i0, &i1, &a);
+            linear_texel_locations(tObj->WrapT, img, height,
+                                   texcoords[i][1], &j0, &j1, &b);
             slice = 0;
             break;
 
          case GL_TEXTURE_1D_ARRAY_EXT:
-            COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoords[i][0],
-                                           u, width, i0, i1);
+            linear_texel_locations(tObj->WrapS, img, width,
+                                   texcoords[i][0], &i0, &i1, &a);
             j0 = clamp_rect_coord_nearest(tObj->WrapT, texcoords[i][1], height);
             j1 = j0;
             slice = 0;
+            break;
 
          case GL_TEXTURE_2D_ARRAY_EXT:
-            COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoords[i][0],
-                                           u, width, i0, i1);
-            COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapT, texcoords[i][1],
-                                           v, height,j0, j1);
+            linear_texel_locations(tObj->WrapS, img, width,
+                                   texcoords[i][0], &i0, &i1, &a);
+            linear_texel_locations(tObj->WrapT, img, height,
+                                   texcoords[i][1], &j0, &j1, &b);
             slice = clamp_rect_coord_nearest(tObj->WrapR, texcoords[i][2], depth);
             break;
          }
@@ -3103,8 +3043,6 @@ sample_depth_texture( GLcontext *ctx,
 
          if (0) {
             /* compute a single weighted depth sample and do one comparison */
-            const GLfloat a = FRAC(u + 1.0F);
-            const GLfloat b = FRAC(v + 1.0F);
             const GLfloat depthSample
                = lerp_2d(a, b, depth00, depth10, depth01, depth11);
             if ((depthSample <= texcoords[i][compare_coord] && function == GL_LEQUAL) ||
@@ -3175,8 +3113,6 @@ sample_depth_texture( GLcontext *ctx,
             case GL_NONE:
                /* ordinary bilinear filtering */
                {
-                  const GLfloat a = FRAC(u + 1.0F);
-                  const GLfloat b = FRAC(v + 1.0F);
                   const GLfloat depthSample
                      = lerp_2d(a, b, depth00, depth10, depth01, depth11);
                   CLAMPED_FLOAT_TO_CHAN(result, depthSample);
@@ -3270,10 +3206,10 @@ sample_depth_texture2(const GLcontext *ctx,
          GLint col, row, ii, jj, imin, imax, jmin, jmax, samples, count;
          GLfloat w;
          GLchan lum;
-         COMPUTE_NEAREST_TEXEL_LOCATION(texObj->WrapS, texcoords[i][0],
-					width, col);
-         COMPUTE_NEAREST_TEXEL_LOCATION(texObj->WrapT, texcoords[i][1],
-					height, row);
+         col = nearest_texel_location(texObj->WrapS, img, width,
+                                      texcoords[i][0]);
+         row = nearest_texel_location(texObj->WrapT, img, height,
+                                      texcoords[i][1]);
 
          imin = col - K;
          imax = col + K;