On 4/16/25 8:32 AM, Paul-Antoine Arras wrote:
Please find attached an updated patch with an additional cost model. By
default, an instruction is 4 and the penalty for moving data from
floating-point to vector register is 2; thus, vfmadd.vf costs 6, which
still makes it cheaper than vec_duplicate + vfmadd.vv. Different tuning
parameters can alter this tradeoff though.
Thanks.
We recently received our own BPI board, so I was able to run
503.bwaves_r on it. Unfortunately, the DIC reduction does not translate
into similar execution time gains. The vector-scalar is only faster by
0.33% on average over 3 iterations.
That's disappointing, but not a huge surprise. Vector FP on the K1/M1
chip in those units is hard to do profitably -- your gains could well be
masked by the overall poor performance profile of those units.
diff --git gcc/config/riscv/riscv.cc gcc/config/riscv/riscv.cc
index 38f3ae7cd84..0f0cf04bdd9 100644
--- gcc/config/riscv/riscv.cc
+++ gcc/config/riscv/riscv.cc
@@ -3864,6 +3864,18 @@ riscv_rtx_costs (rtx x, machine_mode mode, int
outer_code, int opno ATTRIBUTE_UN
if (riscv_v_ext_mode_p (mode))
{
*total = COSTS_N_INSNS (1);
+ if ((GET_CODE (x) == PLUS || GET_CODE (x) == MINUS) && outer_code == SET)
+ {
+ rtx plus_op0 = XEXP (x, 0);
+ if (GET_CODE (plus_op0) == MULT)
+ {
+ rtx mult_op0 = XEXP (plus_op0, 0);
+ if (GET_CODE (mult_op0) == VEC_DUPLICATE)
+ {
+ *total += get_vector_costs ()->regmove->FR2VR;
+ }
+ }
+ }
return true;
}
So this probably needs minor updates now that Pan's code is in, though I
suspect combining your work and his in the costing code will be trivial.
Functionally, I would suggest one change:
if (FLOAT_MODE_P (mode))
*total += get_vector_costs ()->regmove->FR2VR;
else
*total += get_vector_costs ()->regmove->GR2VR;
That way costing ought to work for the vector integer multiply-add/sub
operations as well.
You'll need to double check if FLOAT_MODE_P works on a vector mode, if
not, you may need to get the inner mode.
Otherwise it looks pretty good to me.
Robin, any recommendations from your side?
jeff
