Roland was on PTO. IMO, the change makes sense from a numeric accuracy POV.
I fear this might cause some slowdown with llvmpipe (two muls intead of one), but hopefully it won't be significant. The accuracy issue could cause glitches to llvmpipe too.
Jose On 15/10/15 15:44, Marek Olšák wrote:
Any comment or is this okay with people? Given, "(1-t)*a + t*b", the original code didn't return b for t=1 because it's "floating-point". Marek On Sun, Oct 11, 2015 at 3:29 AM, Marek Olšák <mar...@gmail.com> wrote:From: Marek Olšák <marek.ol...@amd.com> The previous version has precision issues. This can be a problem with tessellation. Sadly, I can't find the article where I read it anymore. I'm not sure if the unsafe-fp-math flag would be enough to revert this. --- src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c index 0ad78b0..512558b 100644 --- a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c +++ b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c @@ -538,12 +538,13 @@ lrp_emit( struct lp_build_tgsi_context * bld_base, struct lp_build_emit_data * emit_data) { - LLVMValueRef tmp; - tmp = lp_build_emit_llvm_binary(bld_base, TGSI_OPCODE_SUB, - emit_data->args[1], - emit_data->args[2]); - emit_data->output[emit_data->chan] = lp_build_emit_llvm_ternary(bld_base, - TGSI_OPCODE_MAD, emit_data->args[0], tmp, emit_data->args[2]); + struct lp_build_context *bld = &bld_base->base; + LLVMValueRef inv, a, b; + + inv = lp_build_sub(bld, bld_base->base.one, emit_data->args[0]); + a = lp_build_mul(bld, emit_data->args[1], emit_data->args[0]); + b = lp_build_mul(bld, emit_data->args[2], inv); + emit_data->output[emit_data->chan] = lp_build_add(bld, a, b); } /* TGSI_OPCODE_MAD */ -- 2.1.4_______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
_______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
