From 6ada4e3a69476ed086955fe4060b894559e1eb95 Mon Sep 17 00:00:00 2001
From: Brian <brian.paul@tungstengraphics.com>
Date: Sat, 27 Oct 2007 09:32:50 -0600
Subject: [PATCH] Comments about texture instructions and the src regs

---
 src/mesa/pipe/tgsi/exec/tgsi_exec.c      | 20 ++++++++++++--------
 src/mesa/state_tracker/st_mesa_to_tgsi.c | 13 ++++++++++---
 2 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/src/mesa/pipe/tgsi/exec/tgsi_exec.c b/src/mesa/pipe/tgsi/exec/tgsi_exec.c
index f577f00..d98f46c 100644
--- a/src/mesa/pipe/tgsi/exec/tgsi_exec.c
+++ b/src/mesa/pipe/tgsi/exec/tgsi_exec.c
@@ -1996,15 +1996,15 @@ exec_instruction(
 
    case TGSI_OPCODE_TEX:
       /* simple texture lookup */
-      /* src[0] is the texcoord */
-      /* src[1] is the sampler unit */
+      /* src[0] = texcoord */
+      /* src[1] = sampler unit */
       exec_tex(mach, inst, FALSE);
       break;
 
    case TGSI_OPCODE_TXB:
       /* Texture lookup with lod bias */
-      /* src[0] is the texcoord (src[0].w = load bias) */
-      /* src[1] is the sampler unit */
+      /* src[0] = texcoord (src[0].w = load bias) */
+      /* src[1] = sampler unit */
       exec_tex(mach, inst, TRUE);
       break;
 
@@ -2013,9 +2013,17 @@ exec_instruction(
       /* src[0] = texcoord */
       /* src[1] = d[strq]/dx */
       /* src[2] = d[strq]/dy */
+      /* src[3] = sampler unit */
       assert (0);
       break;
 
+   case TGSI_OPCODE_TXL:
+      /* Texture lookup with explit LOD */
+      /* src[0] = texcoord (src[0].w = load bias) */
+      /* src[1] = sampler unit */
+      exec_tex(mach, inst, TRUE);
+      break;
+
    case TGSI_OPCODE_UP2H:
       assert (0);
       break;
@@ -2157,10 +2165,6 @@ exec_instruction(
       }
       break;
 
-   case TGSI_OPCODE_TXL:
-      assert (0);
-      break;
-
    case TGSI_OPCODE_IF:
       /* push CondMask */
       assert(mach->CondStackTop < TGSI_EXEC_MAX_COND_NESTING);
diff --git a/src/mesa/state_tracker/st_mesa_to_tgsi.c b/src/mesa/state_tracker/st_mesa_to_tgsi.c
index 131e50b..621159e 100644
--- a/src/mesa/state_tracker/st_mesa_to_tgsi.c
+++ b/src/mesa/state_tracker/st_mesa_to_tgsi.c
@@ -459,6 +459,7 @@ compile_instruction(
       fullinst->Instruction.Opcode = TGSI_OPCODE_SWZ;
       break;
    case OPCODE_TEX:
+      /* ordinary texture lookup */
       fullinst->Instruction.Opcode = TGSI_OPCODE_TEX;
       fullinst->Instruction.NumSrcRegs = 2;
       fullinst->InstructionExtTexture.Texture = map_texture_target( inst->TexSrcTarget );
@@ -466,6 +467,7 @@ compile_instruction(
       fullinst->FullSrcRegisters[1].SrcRegister.Index = inst->TexSrcUnit;
       break;
    case OPCODE_TXB:
+      /* texture lookup with LOD bias */
       fullinst->Instruction.Opcode = TGSI_OPCODE_TXB;
       fullinst->Instruction.NumSrcRegs = 2;
       fullinst->InstructionExtTexture.Texture = map_texture_target( inst->TexSrcTarget );
@@ -473,13 +475,16 @@ compile_instruction(
       fullinst->FullSrcRegisters[1].SrcRegister.Index = inst->TexSrcUnit;
       break;
    case OPCODE_TXD:
+      /* texture lookup with explicit partial derivatives */
       fullinst->Instruction.Opcode = TGSI_OPCODE_TXD;
-      fullinst->Instruction.NumSrcRegs = 2;
+      fullinst->Instruction.NumSrcRegs = 4;
       fullinst->InstructionExtTexture.Texture = map_texture_target( inst->TexSrcTarget );
-      fullinst->FullSrcRegisters[1].SrcRegister.File = TGSI_FILE_SAMPLER;
-      fullinst->FullSrcRegisters[1].SrcRegister.Index = inst->TexSrcUnit;
+      /* src[0] = coord, src[1] = d[strq]/dx, src[2] = d[strq]/dy */
+      fullinst->FullSrcRegisters[3].SrcRegister.File = TGSI_FILE_SAMPLER;
+      fullinst->FullSrcRegisters[3].SrcRegister.Index = inst->TexSrcUnit;
       break;
    case OPCODE_TXL:
+      /* texture lookup with explicit LOD */
       fullinst->Instruction.Opcode = TGSI_OPCODE_TXL;
       fullinst->Instruction.NumSrcRegs = 2;
       fullinst->InstructionExtTexture.Texture = map_texture_target( inst->TexSrcTarget );
@@ -487,6 +492,8 @@ compile_instruction(
       fullinst->FullSrcRegisters[1].SrcRegister.Index = inst->TexSrcUnit;
       break;
    case OPCODE_TXP:
+      /* texture lookup with divide by Q component */
+      /* convert to TEX w/ special flag for division */
       fullinst->Instruction.Opcode = TGSI_OPCODE_TEX;
       fullinst->Instruction.NumSrcRegs = 2;
       fullinst->InstructionExtTexture.Texture = map_texture_target( inst->TexSrcTarget );
-- 
2.7.4