From 743700be1f583db28ff84104754f38bc6852668e Mon Sep 17 00:00:00 2001 From: Jason Ekstrand Date: Fri, 22 Feb 2019 17:06:39 -0600 Subject: [PATCH] nir/builder: Don't emit no-op swizzles The nir_swizzle helper is used some on it's own but it's also called by nir_channel and nir_channels which are used everywhere. It's pretty quick to check while we're walking the swizzle anyway whether or not it's an identity swizzle. If it is, we now don't bother emitting the instruction. Sure, copy-prop will clean it up for us but there's no sense making more work for the optimizer than we have to. Reviewed-by: Ian Romanick --- src/compiler/nir/nir_builder.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/src/compiler/nir/nir_builder.h b/src/compiler/nir/nir_builder.h index c6e80e729a8..253ca5941cb 100644 --- a/src/compiler/nir/nir_builder.h +++ b/src/compiler/nir/nir_builder.h @@ -497,8 +497,16 @@ nir_swizzle(nir_builder *build, nir_ssa_def *src, const unsigned *swiz, assert(num_components <= NIR_MAX_VEC_COMPONENTS); nir_alu_src alu_src = { NIR_SRC_INIT }; alu_src.src = nir_src_for_ssa(src); - for (unsigned i = 0; i < num_components && i < NIR_MAX_VEC_COMPONENTS; i++) + + bool is_identity_swizzle = true; + for (unsigned i = 0; i < num_components && i < NIR_MAX_VEC_COMPONENTS; i++) { + if (swiz[i] != i) + is_identity_swizzle = false; alu_src.swizzle[i] = swiz[i]; + } + + if (num_components == src->num_components && is_identity_swizzle) + return src; return use_fmov ? nir_fmov_alu(build, alu_src, num_components) : nir_imov_alu(build, alu_src, num_components); -- 2.30.2