From 9954f0149799b726b8d57d723328ee5bec2b5070 Mon Sep 17 00:00:00 2001 From: Roland Scheidegger Date: Sat, 15 Feb 2014 03:45:00 +0100 Subject: [PATCH] gallivm: use correct rounding for nearest wrap mode (in the aos int path) The previous code used coords which were calculated as (int) (f_coord * tex_size * 256) >> 8. This is not only unnecessarily complex but can give the wrong texel due to rounding for negative coords (as an example, after denormalization coords from -1.0 to 0.0 should give -1, but this will give -1 for numbers from -1.0-1/256 - 0.0-1/256. Instead, juse use ifloor, dropping the shift stuff. Unfortunately, this will most likely be slower - with arch rounding available it shouldn't be too bad (trades a int shift for a round but also saves an int mul (which is shared by all coords) but otherwise it's a mess. --- .../auxiliary/gallivm/lp_bld_sample_aos.c | 38 +++++-------------- 1 file changed, 9 insertions(+), 29 deletions(-) diff --git a/src/gallium/auxiliary/gallivm/lp_bld_sample_aos.c b/src/gallium/auxiliary/gallivm/lp_bld_sample_aos.c index 4649fa9b957..0d95e4fd787 100644 --- a/src/gallium/auxiliary/gallivm/lp_bld_sample_aos.c +++ b/src/gallium/auxiliary/gallivm/lp_bld_sample_aos.c @@ -567,10 +567,7 @@ lp_build_sample_image_nearest(struct lp_build_sample_context *bld, LLVMValueRef *colors) { const unsigned dims = bld->dims; - LLVMBuilderRef builder = bld->gallivm->builder; struct lp_build_context i32; - LLVMTypeRef i32_vec_type; - LLVMValueRef i32_c8; LLVMValueRef width_vec, height_vec, depth_vec; LLVMValueRef s_ipart, t_ipart = NULL, r_ipart = NULL; LLVMValueRef s_float, t_float = NULL, r_float = NULL; @@ -580,8 +577,6 @@ lp_build_sample_image_nearest(struct lp_build_sample_context *bld, lp_build_context_init(&i32, bld->gallivm, lp_type_int_vec(32, bld->vector_width)); - i32_vec_type = lp_build_vec_type(bld->gallivm, i32.type); - lp_build_extract_image_sizes(bld, &bld->int_size_bld, bld->int_coord_type, @@ -593,39 +588,24 @@ lp_build_sample_image_nearest(struct lp_build_sample_context *bld, s_float = s; t_float = t; r_float = r; if (bld->static_sampler_state->normalized_coords) { - LLVMValueRef scaled_size; LLVMValueRef flt_size; - /* scale size by 256 (8 fractional bits) */ - scaled_size = lp_build_shl_imm(&bld->int_size_bld, int_size, 8); - - flt_size = lp_build_int_to_float(&bld->float_size_bld, scaled_size); + flt_size = lp_build_int_to_float(&bld->float_size_bld, int_size); lp_build_unnormalized_coords(bld, flt_size, &s, &t, &r); } - else { - /* scale coords by 256 (8 fractional bits) */ - s = lp_build_mul_imm(&bld->coord_bld, s, 256); - if (dims >= 2) - t = lp_build_mul_imm(&bld->coord_bld, t, 256); - if (dims >= 3) - r = lp_build_mul_imm(&bld->coord_bld, r, 256); - } /* convert float to int */ - s = LLVMBuildFPToSI(builder, s, i32_vec_type, ""); - if (dims >= 2) - t = LLVMBuildFPToSI(builder, t, i32_vec_type, ""); - if (dims >= 3) - r = LLVMBuildFPToSI(builder, r, i32_vec_type, ""); - - /* compute floor (shift right 8) */ - i32_c8 = lp_build_const_int_vec(bld->gallivm, i32.type, 8); - s_ipart = LLVMBuildAShr(builder, s, i32_c8, ""); + /* For correct rounding, need floor, not truncation here. + * Note that in some cases (clamp to edge, no texel offsets) we + * could use a non-signed build context which would help archs + * greatly which don't have arch rounding. + */ + s_ipart = lp_build_ifloor(&bld->coord_bld, s); if (dims >= 2) - t_ipart = LLVMBuildAShr(builder, t, i32_c8, ""); + t_ipart = lp_build_ifloor(&bld->coord_bld, t); if (dims >= 3) - r_ipart = LLVMBuildAShr(builder, r, i32_c8, ""); + r_ipart = lp_build_ifloor(&bld->coord_bld, r); /* add texel offsets */ if (offsets[0]) { -- 2.30.2