tgsi: add new tgsi_two_side.c utility code

This could be used by any driver where the device doesn't directly
support two-sided lighting.  This code modifies a fragment shader
to accecpt back-face colors and choose between the front/back colors
depending on the triangle's front-face sign.

3 files changed, 264 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/Makefile.sources b/src/gallium/auxiliary/Makefile.sources
index 3616d885b47..d5986b45e06 100644
--- a/src/gallium/auxiliary/Makefile.sources
+++ b/src/gallium/auxiliary/Makefile.sources
@@ -154,6 +154,8 @@ C_SOURCES := \
 	tgsi/tgsi_text.h \
 	tgsi/tgsi_transform.c \
 	tgsi/tgsi_transform.h \
+	tgsi/tgsi_two_side.c \
+	tgsi/tgsi_two_side.h \
 	tgsi/tgsi_ureg.c \
 	tgsi/tgsi_ureg.h \
 	tgsi/tgsi_util.c \
diff --git a/src/gallium/auxiliary/tgsi/tgsi_two_side.c b/src/gallium/auxiliary/tgsi/tgsi_two_side.c
new file mode 100644
index 00000000000..2406e2876f3
--- /dev/null
+++ b/src/gallium/auxiliary/tgsi/tgsi_two_side.c
@@ -0,0 +1,228 @@
+/*
+ * Copyright 2013 VMware, Inc.
+ * 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"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+/**
+ * This utility transforms fragment shaders to facilitate two-sided lighting.
+ *
+ * Basically, if the FS has any color inputs (TGSI_SEMANTIC_COLOR) we'll:
+ * 1. create corresponding back-color inputs (TGSI_SEMANTIC_BCOLOR)
+ * 2. use the FACE register to choose between front/back colors and put the
+ *    selected color in new temp regs.
+ * 3. replace reads of the original color inputs with the new temp regs.
+ *
+ * Then, the driver just needs to link the VS front/back output colors to
+ * the FS front/back input colors.
+ */
+
+#include "util/u_debug.h"
+#include "util/u_math.h"
+#include "tgsi_info.h"
+#include "tgsi_two_side.h"
+#include "tgsi_transform.h"
+
+
+#define INVALID_INDEX 9999
+
+
+struct two_side_transform_context
+{
+   struct tgsi_transform_context base;
+   uint num_temps;
+   uint num_inputs;
+   uint face_input;           /**< index of the FACE input */
+   uint front_color_input[2]; /**< INPUT regs */
+   uint front_color_interp[2];/**< TGSI_INTERPOLATE_x */
+   uint back_color_input[2];  /**< INPUT regs */
+   uint new_colors[2];        /**< TEMP regs */
+};
+
+
+static inline struct two_side_transform_context *
+two_side_transform_context(struct tgsi_transform_context *ctx)
+{
+   return (struct two_side_transform_context *) ctx;
+}
+
+
+static void
+xform_decl(struct tgsi_transform_context *ctx,
+           struct tgsi_full_declaration *decl)
+{
+   struct two_side_transform_context *ts = two_side_transform_context(ctx);
+
+   if (decl->Declaration.File == TGSI_FILE_INPUT) {
+      if (decl->Semantic.Name == TGSI_SEMANTIC_COLOR) {
+         /* found a front color */
+         assert(decl->Semantic.Index < 2);
+         ts->front_color_input[decl->Semantic.Index] = decl->Range.First;
+         ts->front_color_interp[decl->Semantic.Index] = decl->Interp.Interpolate;
+      }
+      else if (decl->Semantic.Name == TGSI_SEMANTIC_FACE) {
+         ts->face_input = decl->Range.First;
+      }
+      ts->num_inputs = MAX2(ts->num_inputs, decl->Range.Last + 1);
+   }
+   else if (decl->Declaration.File == TGSI_FILE_TEMPORARY) {
+      ts->num_temps = MAX2(ts->num_temps, decl->Range.Last + 1);
+   }
+
+   ctx->emit_declaration(ctx, decl);
+}
+
+
+static void
+emit_prolog(struct tgsi_transform_context *ctx)
+{
+   struct two_side_transform_context *ts = two_side_transform_context(ctx);
+   struct tgsi_full_declaration decl;
+   struct tgsi_full_instruction inst;
+   uint num_colors = 0;
+   uint i;
+
+   /* Declare 0, 1 or 2 new BCOLOR inputs */
+   for (i = 0; i < 2; i++) {
+      if (ts->front_color_input[i] != INVALID_INDEX) {
+         decl = tgsi_default_full_declaration();
+         decl.Declaration.File = TGSI_FILE_INPUT;
+         decl.Declaration.Interpolate = 1;
+         decl.Declaration.Semantic = 1;
+         decl.Semantic.Name = TGSI_SEMANTIC_BCOLOR;
+         decl.Semantic.Index = i;
+         decl.Range.First = decl.Range.Last = ts->num_inputs++;
+         decl.Interp.Interpolate = ts->front_color_interp[i];
+         ctx->emit_declaration(ctx, &decl);
+         ts->back_color_input[i] = decl.Range.First;
+         num_colors++;
+      }
+   }
+
+   if (num_colors > 0) {
+      /* Declare 1 or 2 temp registers */
+      decl = tgsi_default_full_declaration();
+      decl.Declaration.File = TGSI_FILE_TEMPORARY;
+      decl.Range.First = ts->num_temps;
+      decl.Range.Last = ts->num_temps + num_colors - 1;
+      ctx->emit_declaration(ctx, &decl);
+      ts->new_colors[0] = ts->num_temps;
+      ts->new_colors[1] = ts->num_temps + 1;
+
+      if (ts->face_input == INVALID_INDEX) {
+         /* declare FACE INPUT register */
+         decl = tgsi_default_full_declaration();
+         decl.Declaration.File = TGSI_FILE_INPUT;
+         decl.Declaration.Semantic = 1;
+         decl.Semantic.Name = TGSI_SEMANTIC_FACE;
+         decl.Semantic.Index = 0;
+         decl.Range.First = decl.Range.Last = ts->num_inputs++;
+         ctx->emit_declaration(ctx, &decl);
+         ts->face_input = decl.Range.First;
+      }
+
+      /* CMP temp[c0], face, bcolor[c0], fcolor[c0]
+       * temp[c0] = face < 0.0 ? bcolor[c0] : fcolor[c0]
+       */
+      for (i = 0; i < 2; i++) {
+         if (ts->front_color_input[i] != INVALID_INDEX) {
+            inst = tgsi_default_full_instruction();
+            inst.Instruction.Opcode = TGSI_OPCODE_CMP;
+            inst.Instruction.NumDstRegs = 1;
+            inst.Dst[0].Register.File = TGSI_FILE_TEMPORARY;
+            inst.Dst[0].Register.Index = ts->new_colors[i];
+            inst.Instruction.NumSrcRegs = 3;
+            inst.Src[0].Register.File = TGSI_FILE_INPUT;
+            inst.Src[0].Register.Index = ts->face_input;
+            inst.Src[1].Register.File = TGSI_FILE_INPUT;
+            inst.Src[1].Register.Index = ts->back_color_input[i];
+            inst.Src[2].Register.File = TGSI_FILE_INPUT;
+            inst.Src[2].Register.Index = ts->front_color_input[i];
+
+            ctx->emit_instruction(ctx, &inst);
+         }
+      }
+   }
+}
+
+
+static void
+xform_inst(struct tgsi_transform_context *ctx,
+           struct tgsi_full_instruction *inst)
+{
+   struct two_side_transform_context *ts = two_side_transform_context(ctx);
+   const struct tgsi_opcode_info *info =
+      tgsi_get_opcode_info(inst->Instruction.Opcode);
+   uint i, j;
+
+   /* Look for src regs which reference the input color and replace
+    * them with the temp color.
+    */
+   for (i = 0; i < info->num_src; i++) {
+      if (inst->Src[i].Register.File == TGSI_FILE_INPUT) {
+         for (j = 0; j < 2; j++) {
+            if (inst->Src[i].Register.Index == ts->front_color_input[j]) {
+               /* replace color input with temp reg */
+               inst->Src[i].Register.File = TGSI_FILE_TEMPORARY;
+               inst->Src[i].Register.Index = ts->new_colors[j];
+               break;
+            }
+         }
+      }
+   }
+
+   ctx->emit_instruction(ctx, inst);
+}
+
+
+struct tgsi_token *
+tgsi_add_two_side(const struct tgsi_token *tokens_in)
+{
+   struct two_side_transform_context transform;
+   const uint num_new_tokens = 100; /* should be enough */
+   const uint new_len = tgsi_num_tokens(tokens_in) + num_new_tokens;
+   struct tgsi_token *new_tokens;
+
+   /* setup transformation context */
+   memset(&transform, 0, sizeof(transform));
+   transform.base.transform_declaration = xform_decl;
+   transform.base.transform_instruction = xform_inst;
+   transform.base.prolog = emit_prolog;
+   transform.face_input = INVALID_INDEX;
+   transform.front_color_input[0] = INVALID_INDEX;
+   transform.front_color_input[1] = INVALID_INDEX;
+   transform.front_color_interp[0] = TGSI_INTERPOLATE_COLOR;
+   transform.front_color_interp[1] = TGSI_INTERPOLATE_COLOR;
+   transform.back_color_input[0] = INVALID_INDEX;
+   transform.back_color_input[1] = INVALID_INDEX;
+
+   /* allocate new tokens buffer */
+   new_tokens = tgsi_alloc_tokens(new_len);
+   if (!new_tokens)
+      return NULL;
+
+   /* transform the shader */
+   tgsi_transform_shader(tokens_in, new_tokens, new_len, &transform.base);
+
+   return new_tokens;
+}
diff --git a/src/gallium/auxiliary/tgsi/tgsi_two_side.h b/src/gallium/auxiliary/tgsi/tgsi_two_side.h
new file mode 100644
index 00000000000..bac239e41af
--- /dev/null
+++ b/src/gallium/auxiliary/tgsi/tgsi_two_side.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2013 VMware, Inc.
+ * 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"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef TGSI_TWO_SIDE_H
+#define TGSI_TWO_SIDE_H
+
+struct tgsi_token;
+
+struct tgsi_token *
+tgsi_add_two_side(const struct tgsi_token *tokens_in);
+
+#endif /* TGSI_TWO_SIDE_H */