在 2022/3/30 下午6:02, eop Chen 写道:
Weiwei Li <liwei...@iscas.ac.cn <mailto:liwei...@iscas.ac.cn>> 於
2022年3月30日 下午4:27 寫道：
在 2022/3/30 下午3:42, 陳約廷 写道:
Weiwei Li <liwei...@iscas.ac.cn <mailto:liwei...@iscas.ac.cn>> 於
2022年3月28日 下午7:56 寫道：
在 2022/3/7 下午3:10, ~eopxd 写道:
From: eopXD <eop.c...@sifive.com <mailto:eop.c...@sifive.com>>
Another question: max_elems is equal to total_elems when lmul >= 0.
So max_elems can be reused here instead of caculating total_elems again.
I don’t understand your second question though. If nf = 3, there
will be 3 registers
involved with the instruction (namely reg, reg+1, reg+2). Why do we
care about
(reg+3)?
I just consider register group here. Reg, reg+1, reg+2 and reg+3 may
belong to the same register group.
Regards,
Weiwei Li
According to v-spec (under section 7.8):
Each field will be held in successively numbered vector register
groups. When EMUL>1
each field will occupy a vector register group held in multiple
successively numbered
vector registers, and the vector register group for each field
must follow the usual vector
register alignment constraints (e.g., when EMUL=2 and NFIELDS=4,
each field’s vector
register group must start at an even vector register, but does not
have to start at a multiple
of 8 vector register number).
I think the spec has explained itself that NFIELDS represents the
number of register groups involved
in this instruction. Therefore in a register group of 4 (LMUL = m2),
NFIELD should be no more than 2.
The `vlmax` here would be (VLEN * 4 / EEW). In this sense, if the `vl`
provided for the vector instruction
is within the range 2 * vlmax / 4 <= vl <= 3 * vlmax / 4, the elements
in the 4th register (namely reg+3)
will all be counted as tail elements.
I hope this answers your question.
OK, Thanks a lot. This truly answers my question, even though what I
really want to know is the case for EMUL=1, and NFIELDS=3.
since NFIELDS represents the number of register groups, not take the
total of EMUL * NFIELDS into one register group ,
so reg+3 should not take into tail elements for my case.
Regards,
Weiwei Li
Regards,
eop Chen
