From: Roland Scheidegger <srol...@vmware.com> We use 128bit vector interleave for untwiddling in the blend code (with 256bit vectors). llvm generates terrible code for this for some reason, so instead of generating a shuffle for 2 128bit vectors use a extract/insert shuffle instead (it only seems to matter we're not using 128bit wide vectors for the shuffle). This decreases instruction count of the blend code generated for a rgba8 render target without blending from 169 to 113 with llvm 3.1 and from 136 to 114 in llvm 3.2/3.3, and I got a ~8% (llvm 3.1) and ~5% (3.2/3.3) performance improvement in gears. (The generated code is still not terribly good as we could actually avoid the interleaving completely but llvm can't know this.) --- src/gallium/auxiliary/gallivm/lp_bld_pack.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_pack.c b/src/gallium/auxiliary/gallivm/lp_bld_pack.c index 14fcd38..f660165 100644 --- a/src/gallium/auxiliary/gallivm/lp_bld_pack.c +++ b/src/gallium/auxiliary/gallivm/lp_bld_pack.c @@ -271,6 +271,28 @@ lp_build_interleave2(struct gallivm_state *gallivm, { LLVMValueRef shuffle; + if (type.length == 2 && type.width == 128 && util_cpu_caps.has_avx) { + /* + * This is a workaround for llvm code generation deficiency. Strangely + * enough, while this needs vinsertf128/vextractf128 instructions (hence + * a natural match when using 2x128bit vectors) the "normal" unpack shuffle + * generates code ranging from atrocious (llvm 3.1) to terrible (llvm 3.2, 3.3). + * So use some different shuffles instead (the exact shuffles don't seem to + * matter, as long as not using 128bit wide vectors, works with 8x32 or 4x64). + */ + struct lp_type tmp_type = type; + LLVMValueRef srchalf[2], tmpdst; + tmp_type.length = 4; + tmp_type.width = 64; + a = LLVMBuildBitCast(gallivm->builder, a, lp_build_vec_type(gallivm, tmp_type), ""); + b = LLVMBuildBitCast(gallivm->builder, b, lp_build_vec_type(gallivm, tmp_type), ""); + srchalf[0] = lp_build_extract_range(gallivm, a, lo_hi * 2, 2); + srchalf[1] = lp_build_extract_range(gallivm, b, lo_hi * 2, 2); + tmp_type.length = 2; + tmpdst = lp_build_concat(gallivm, srchalf, tmp_type, 2); + return LLVMBuildBitCast(gallivm->builder, tmpdst, lp_build_vec_type(gallivm, type), ""); + + } shuffle = lp_build_const_unpack_shuffle(gallivm, type.length, lo_hi); return LLVMBuildShuffleVector(gallivm->builder, a, b, shuffle, ""); -- 1.7.9.5 _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev