Module: Mesa Branch: master Commit: 8dcbca59572a856ca554af9ab3f52120b6f2a929 URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=8dcbca59572a856ca554af9ab3f52120b6f2a929
Author: Jason Ekstrand <[email protected]> Date: Tue Sep 22 21:32:06 2015 -0700 nir/lower_vec_to_movs: Don't emit unneeded movs It's possible that, if a vecN operation is involved in a phi node, that we could end up moving from a register to itself. If swizzling is involved, we need to emit the move but. However, if there is no swizzling, then the mov is a no-op and we might as well not bother emitting it. Shader-db results on Haswell: total instructions in shared programs: 6262536 -> 6259558 (-0.05%) instructions in affected programs: 184780 -> 181802 (-1.61%) helped: 838 HURT: 0 Reviewed-by: Eduardo Lima Mitev <[email protected]> Reviewed-by: Matt Turner <[email protected]> --- src/glsl/nir/nir_lower_vec_to_movs.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/src/glsl/nir/nir_lower_vec_to_movs.c b/src/glsl/nir/nir_lower_vec_to_movs.c index 287f2bf..c08b721 100644 --- a/src/glsl/nir/nir_lower_vec_to_movs.c +++ b/src/glsl/nir/nir_lower_vec_to_movs.c @@ -83,7 +83,25 @@ insert_mov(nir_alu_instr *vec, unsigned start_idx, nir_shader *shader) } } - nir_instr_insert_before(&vec->instr, &mov->instr); + /* In some situations (if the vecN is involved in a phi-web), we can end + * up with a mov from a register to itself. Some of those channels may end + * up doing nothing and there's no reason to have them as part of the mov. + */ + if (src_matches_dest_reg(&mov->dest.dest, &mov->src[0].src) && + !mov->src[0].abs && !mov->src[0].negate) { + for (unsigned i = 0; i < 4; i++) { + if (mov->src[0].swizzle[i] == i) { + mov->dest.write_mask &= ~(1 << i); + } + } + } + + /* Only emit the instruction if it actually does something */ + if (mov->dest.write_mask) { + nir_instr_insert_before(&vec->instr, &mov->instr); + } else { + ralloc_free(mov); + } return mov->dest.write_mask; } _______________________________________________ mesa-commit mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/mesa-commit
