radeonsi: fix Gather4 with integer formats

The closed compiler does the same thing.

This fixes: GL45-CTS.texture_gather.*-int-* (18 tests)

Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index 1ef3b70..0b7de18 100644 (file)
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -4724,16 +4724,86 @@ static void tex_fetch_args(
                           samp_ptr, address, count, dmask);
 }
 
+/* Gather4 should follow the same rules as bilinear filtering, but the hardware
+ * incorrectly forces nearest filtering if the texture format is integer.
+ * The only effect it has on Gather4, which always returns 4 texels for
+ * bilinear filtering, is that the final coordinates are off by 0.5 of
+ * the texel size.
+ *
+ * The workaround is to subtract 0.5 from the unnormalized coordinates,
+ * or (0.5 / size) from the normalized coordinates.
+ */
+static void si_lower_gather4_integer(struct si_shader_context *ctx,
+                                    struct lp_build_emit_data *emit_data,
+                                    const char *intr_name,
+                                    unsigned coord_vgpr_index)
+{
+       LLVMBuilderRef builder = ctx->radeon_bld.gallivm.builder;
+       LLVMValueRef coord = emit_data->args[0];
+       LLVMValueRef half_texel[2];
+       int c;
+
+       if (emit_data->inst->Texture.Texture == TGSI_TEXTURE_RECT ||
+           emit_data->inst->Texture.Texture == TGSI_TEXTURE_SHADOWRECT) {
+               half_texel[0] = half_texel[1] = LLVMConstReal(ctx->f32, -0.5);
+       } else {
+               struct tgsi_full_instruction txq_inst = {};
+               struct lp_build_emit_data txq_emit_data = {};
+
+               /* Query the texture size. */
+               txq_inst.Texture.Texture = emit_data->inst->Texture.Texture;
+               txq_emit_data.inst = &txq_inst;
+               txq_emit_data.dst_type = ctx->v4i32;
+               set_tex_fetch_args(ctx, &txq_emit_data, TGSI_OPCODE_TXQ,
+                                  txq_inst.Texture.Texture,
+                                  emit_data->args[1], NULL,
+                                  &ctx->radeon_bld.soa.bld_base.uint_bld.zero,
+                                  1, 0xf);
+               txq_emit(NULL, &ctx->radeon_bld.soa.bld_base, &txq_emit_data);
+
+               /* Compute -0.5 / size. */
+               for (c = 0; c < 2; c++) {
+                       half_texel[c] =
+                               LLVMBuildExtractElement(builder, txq_emit_data.output[0],
+                                                       LLVMConstInt(ctx->i32, c, 0), "");
+                       half_texel[c] = LLVMBuildUIToFP(builder, half_texel[c], ctx->f32, "");
+                       half_texel[c] =
+                               lp_build_emit_llvm_unary(&ctx->radeon_bld.soa.bld_base,
+                                                        TGSI_OPCODE_RCP, half_texel[c]);
+                       half_texel[c] = LLVMBuildFMul(builder, half_texel[c],
+                                                     LLVMConstReal(ctx->f32, -0.5), "");
+               }
+       }
+
+       for (c = 0; c < 2; c++) {
+               LLVMValueRef tmp;
+               LLVMValueRef index = LLVMConstInt(ctx->i32, coord_vgpr_index + c, 0);
+
+               tmp = LLVMBuildExtractElement(builder, coord, index, "");
+               tmp = LLVMBuildBitCast(builder, tmp, ctx->f32, "");
+               tmp = LLVMBuildFAdd(builder, tmp, half_texel[c], "");
+               tmp = LLVMBuildBitCast(builder, tmp, ctx->i32, "");
+               coord = LLVMBuildInsertElement(builder, coord, tmp, index, "");
+       }
+
+       emit_data->args[0] = coord;
+       emit_data->output[emit_data->chan] =
+               lp_build_intrinsic(builder, intr_name, emit_data->dst_type,
+                                  emit_data->args, emit_data->arg_count,
+                                  LLVMReadNoneAttribute);
+}
+
 static void build_tex_intrinsic(const struct lp_build_tgsi_action *action,
                                struct lp_build_tgsi_context *bld_base,
                                struct lp_build_emit_data *emit_data)
 {
        struct si_shader_context *ctx = si_shader_context(bld_base);
        struct lp_build_context *base = &bld_base->base;
-       unsigned opcode = emit_data->inst->Instruction.Opcode;
-       unsigned target = emit_data->inst->Texture.Texture;
+       const struct tgsi_full_instruction *inst = emit_data->inst;
+       unsigned opcode = inst->Instruction.Opcode;
+       unsigned target = inst->Texture.Texture;
        char intr_name[127];
-       bool has_offset = emit_data->inst->Texture.NumOffsets > 0;
+       bool has_offset = inst->Texture.NumOffsets > 0;
        bool is_shadow = tgsi_is_shadow_target(target);
        char type[64];
        const char *name = "llvm.SI.image.sample";
@@ -4795,6 +4865,29 @@ static void build_tex_intrinsic(const struct lp_build_tgsi_action *action,
                name, is_shadow ? ".c" : "", infix,
                has_offset ? ".o" : "", type);
 
+       /* The hardware needs special lowering for Gather4 with integer formats. */
+       if (opcode == TGSI_OPCODE_TG4) {
+               struct tgsi_shader_info *info = &ctx->shader->selector->info;
+               /* This will also work with non-constant indexing because of how
+                * glsl_to_tgsi works and we intent to preserve that behavior.
+                */
+               const unsigned src_idx = 2;
+               unsigned sampler = inst->Src[src_idx].Register.Index;
+
+               assert(inst->Src[src_idx].Register.File == TGSI_FILE_SAMPLER);
+
+               if (info->sampler_type[sampler] == TGSI_RETURN_TYPE_SINT ||
+                   info->sampler_type[sampler] == TGSI_RETURN_TYPE_UINT) {
+                       /* Texture coordinates start after:
+                        *   {offset, bias, z-compare, derivatives}
+                        * Only the offset and z-compare can occur here.
+                        */
+                       si_lower_gather4_integer(ctx, emit_data, intr_name,
+                                                (int)has_offset + (int)is_shadow);
+                       return;
+               }
+       }
+
        emit_data->output[emit_data->chan] = lp_build_intrinsic(
                base->gallivm->builder, intr_name, emit_data->dst_type,
                emit_data->args, emit_data->arg_count,