radeonsi: implement SAMPLEPOS fragment shader input

The sample positions are read from a constant buffer.

2 files changed, 48 insertions, 0 deletions

diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index d021caaa6c4..6818106ece7 100644
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -557,6 +557,8 @@ static void declare_system_value(
 {
 	struct si_shader_context *si_shader_ctx =
 		si_shader_context(&radeon_bld->soa.bld_base);
+	struct lp_build_context *uint_bld = &radeon_bld->soa.bld_base.uint_bld;
+	struct gallivm_state *gallivm = &radeon_bld->gallivm;
 	LLVMValueRef value = 0;
 
 	switch (decl->Semantic.Name) {
@@ -574,6 +576,27 @@ static void declare_system_value(
 		value = get_sample_id(radeon_bld);
 		break;
 
+	case TGSI_SEMANTIC_SAMPLEPOS:
+	{
+		LLVMBuilderRef builder = gallivm->builder;
+		LLVMValueRef desc = LLVMGetParam(si_shader_ctx->radeon_bld.main_fn, SI_PARAM_CONST);
+		LLVMValueRef buf_index = lp_build_const_int32(gallivm, NUM_PIPE_CONST_BUFFERS);
+		LLVMValueRef resource = build_indexed_load(si_shader_ctx, desc, buf_index);
+
+		/* offset = sample_id * 8  (8 = 2 floats containing samplepos.xy) */
+		LLVMValueRef offset0 = lp_build_mul_imm(uint_bld, get_sample_id(radeon_bld), 8);
+		LLVMValueRef offset1 = LLVMBuildAdd(builder, offset0, lp_build_const_int32(gallivm, 4), "");
+
+		LLVMValueRef pos[4] = {
+			load_const(builder, resource, offset0, radeon_bld->soa.bld_base.base.elem_type),
+			load_const(builder, resource, offset1, radeon_bld->soa.bld_base.base.elem_type),
+			lp_build_const_float(gallivm, 0),
+			lp_build_const_float(gallivm, 0)
+		};
+		value = lp_build_gather_values(gallivm, pos, 4);
+		break;
+	}
+
 	default:
 		assert(!"unknown system value");
 		return;
diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
index c08d7034c55..b85a4594156 100644
--- a/src/gallium/drivers/radeonsi/si_state.c
+++ b/src/gallium/drivers/radeonsi/si_state.c
@@ -1859,6 +1859,7 @@ static void si_set_framebuffer_state(struct pipe_context *ctx,
 				     const struct pipe_framebuffer_state *state)
 {
 	struct si_context *sctx = (struct si_context *)ctx;
+	struct pipe_constant_buffer constbuf = {0};
 	struct r600_surface *surf = NULL;
 	struct r600_texture *rtex;
 	int i;
@@ -1924,6 +1925,30 @@ static void si_set_framebuffer_state(struct pipe_context *ctx,
 	sctx->framebuffer.atom.num_dw += 18; /* MSAA sample locations */
 	sctx->framebuffer.atom.dirty = true;
 	sctx->msaa_config.dirty = true;
+
+	/* Set sample locations as fragment shader constants. */
+	switch (sctx->framebuffer.nr_samples) {
+	case 1:
+		constbuf.user_buffer = sctx->b.sample_locations_1x;
+		break;
+	case 2:
+		constbuf.user_buffer = sctx->b.sample_locations_2x;
+		break;
+	case 4:
+		constbuf.user_buffer = sctx->b.sample_locations_4x;
+		break;
+	case 8:
+		constbuf.user_buffer = sctx->b.sample_locations_8x;
+		break;
+	case 16:
+		constbuf.user_buffer = sctx->b.sample_locations_16x;
+		break;
+	default:
+		assert(0);
+	}
+	constbuf.buffer_size = sctx->framebuffer.nr_samples * 2 * 4;
+	ctx->set_constant_buffer(ctx, PIPE_SHADER_FRAGMENT,
+				 NUM_PIPE_CONST_BUFFERS, &constbuf);
 }
 
 static void si_emit_framebuffer_state(struct si_context *sctx, struct r600_atom *atom)