From b1ed7202dfb64c01313e78bd4fe290ecd08bf5f7 Mon Sep 17 00:00:00 2001 From: Roland Scheidegger Date: Wed, 31 Jul 2013 16:57:50 +0200 Subject: [PATCH] gallivm: use nearest rounding for float->unorm24 conversion Previously we were using truncation, which gives the correct result only for numbers in [0.5-1.0] range (because there's no mantissa bits to do any rounding there). This is frequently hit (and probably only used there) when converting fragment depth to depth format (d24s8 etc.) or otherwise dealing with depth format. v2: as spotted by Jose, get rid of extra type (src_type is already unsigned). Reviewed-by: Jose Fonseca --- src/gallium/auxiliary/gallivm/lp_bld_conv.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/src/gallium/auxiliary/gallivm/lp_bld_conv.c b/src/gallium/auxiliary/gallivm/lp_bld_conv.c index ba51ff794f6..712ce5f92dc 100644 --- a/src/gallium/auxiliary/gallivm/lp_bld_conv.c +++ b/src/gallium/auxiliary/gallivm/lp_bld_conv.c @@ -266,17 +266,19 @@ lp_build_clamped_float_to_unsigned_norm(struct gallivm_state *gallivm, else if (dst_width == (mantissa + 1)) { /* * The destination width matches exactly what can be represented in - * floating point (i.e., mantissa + 1 bits). So do a straight - * multiplication followed by casting. No further rounding is necessary. + * floating point (i.e., mantissa + 1 bits). Even so correct rounding + * still needs to be applied (only for numbers in [0.5-1.0] would + * conversion using truncation after scaling be sufficient). */ - double scale; + struct lp_build_context uf32_bld; + lp_build_context_init(&uf32_bld, gallivm, src_type); scale = (double)((1ULL << dst_width) - 1); res = LLVMBuildFMul(builder, src, lp_build_const_vec(gallivm, src_type, scale), ""); - res = LLVMBuildFPToSI(builder, res, int_vec_type, ""); + res = lp_build_iround(&uf32_bld, res); } else { /* -- 2.30.2