[Mesa-dev] [PATCH v3 1/2] r600: correct texture offset for array index lookup

[Gert Wollny]

From: Gert Wollny <gw.fossdev at gmail.com>

For texture array lookup the slice index is evaluated according to
  idx = floor(z + 0.5)

This patch implements the first part by adding 0.5 to the according
texture coordinate when appropriate.

Fixes multi-sample tests out of:
  dEQP-GLES3.functional.texture.shadow.2d_array.*
  dEQP-GLES3.functional.texture.vertex.2d_array.*
  dEQP-GLES3.functional.texture.filtering.2d_array.*
(In the multi-sample case the rounding accuracy is not tested.)

v2: - Don't apply texture offset correction for GATHER*O (corrects piglit
      failures reported by Dave Airlie)
    - unconditionally set the texture offset to 1 (=0.5) because the shader
      can't set an offset for the array index (Roland Scheidegger)

v3: - Set texture offset also for GATHER*0 via SET_TEXTURE_OFFSET to be
      consistent for all GATHER operations (thanks Roland Scheidegger for
      pointing out this inconsistency).
    - Don't set the offset for GET_TEXTURE_RESINFO operations
    - correct typos (Roland)

Acked-by: Roland Scheidegger <sroland at vmware.com> (v2)
Signed-off-by: Gert Wollny <gert.wollny at collabora.com>
---
 src/gallium/drivers/r600/r600_shader.c | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/r600/r600_shader.c b/src/gallium/drivers/r600/r600_shader.c
index c466a48262..ffc272cf6f 100644
--- a/src/gallium/drivers/r600/r600_shader.c
+++ b/src/gallium/drivers/r600/r600_shader.c
@@ -7456,6 +7456,7 @@ static int tgsi_tex(struct r600_shader_ctx *ctx)
 	int8_t offset_x = 0, offset_y = 0, offset_z = 0;
 	boolean has_txq_cube_array_z = false;
 	unsigned sampler_index_mode;
+	int *array_index_offset = NULL;
 
 	if (inst->Instruction.Opcode == TGSI_OPCODE_TXQ &&
 	    ((inst->Texture.Texture == TGSI_TEXTURE_CUBE_ARRAY ||
@@ -8251,7 +8252,15 @@ static int tgsi_tex(struct r600_shader_ctx *ctx)
 		tex.src_gpr = ctx->file_offset[inst->TexOffsets[0].File] + inst->TexOffsets[0].Index;
 		tex.src_sel_x = inst->TexOffsets[0].SwizzleX;
 		tex.src_sel_y = inst->TexOffsets[0].SwizzleY;
-		tex.src_sel_z = inst->TexOffsets[0].SwizzleZ;
+
+		if (inst->Texture.Texture == TGSI_TEXTURE_2D_ARRAY ||
+		    inst->Texture.Texture == TGSI_TEXTURE_SHADOW2D_ARRAY ||
+		    inst->Texture.Texture == TGSI_TEXTURE_CUBE_ARRAY ||
+		    inst->Texture.Texture == TGSI_TEXTURE_SHADOWCUBE_ARRAY)
+			tex.src_sel_z = PIPE_SWIZZLE_1;
+		else
+			tex.src_sel_z = inst->TexOffsets[0].SwizzleZ;
+		
 		tex.src_sel_w = 4;
 
 		tex.dst_sel_x = 7;
@@ -8411,18 +8420,34 @@ static int tgsi_tex(struct r600_shader_ctx *ctx)
 		    opcode == FETCH_OP_SAMPLE_C_LB) {
 			/* the array index is read from Y */
 			tex.coord_type_y = 0;
+			array_index_offset = &tex.offset_y;
 		} else {
 			/* the array index is read from Z */
 			tex.coord_type_z = 0;
 			tex.src_sel_z = tex.src_sel_y;
+			array_index_offset = &tex.offset_z;
+
 		}
 	} else if (inst->Texture.Texture == TGSI_TEXTURE_2D_ARRAY ||
 		   inst->Texture.Texture == TGSI_TEXTURE_SHADOW2D_ARRAY ||
 		   ((inst->Texture.Texture == TGSI_TEXTURE_CUBE_ARRAY ||
 		    inst->Texture.Texture == TGSI_TEXTURE_SHADOWCUBE_ARRAY) &&
-		    (ctx->bc->chip_class >= EVERGREEN)))
+		    (ctx->bc->chip_class >= EVERGREEN))) {
 		/* the array index is read from Z */
 		tex.coord_type_z = 0;
+		array_index_offset = &tex.offset_z;
+	}
+
+	/* We have array access, the coordinates are not int and we use the
+	 * offset registers -> add 0.5 to the array index to adjust it according
+	 * to floor(z + 0.5). The floor operation is set as TRUNC in the texture
+	 * state.
+	 */
+	if (array_index_offset &&
+	    opcode != FETCH_OP_LD && opcode != FETCH_OP_GET_TEXTURE_RESINFO &&
+	    opcode != FETCH_OP_GATHER4_C_O && opcode != FETCH_OP_GATHER4_O) {
+		*array_index_offset = 1;
+	}
 
 	/* mask unused source components */
 	if (opcode == FETCH_OP_SAMPLE || opcode == FETCH_OP_GATHER4) {
-- 
2.16.4