Xi Ruoyao <xry...@xry111.site> 于2024年2月5日周一 02:01写道：
>
> We expanded (neg x) to (minus const0 x) for MSA FP vectors, this is
> wrong because -0.0 is not 0 - 0.0. This causes some Python tests to
> fail when Python is built with MSA enabled.
>
> Use the bnegi.df instructions to simply reverse the sign bit instead.
>
> gcc/ChangeLog:
>
> * config/mips/mips-msa.md (elmsgnbit): New define_mode_attr.
> (neg<mode>2): Change the mode iterator from MSA to IMSA because
> in FP arithmetic we cannot use (0 - x) for -x.
> (neg<mode>2): New define_insn to implement FP vector negation,
> using a bnegi instruction to negate the sign bit.
> ---
>
> Bootstrapped and regtested on mips64el-linux-gnuabi64. Ok for trunk
> and/or release branches?
>
> gcc/config/mips/mips-msa.md | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
LGTM, while I guess that we also need a test case.
> diff --git a/gcc/config/mips/mips-msa.md b/gcc/config/mips/mips-msa.md
> index 83d9a08e360..920161ed1d8 100644
> --- a/gcc/config/mips/mips-msa.md
> +++ b/gcc/config/mips/mips-msa.md
> @@ -231,6 +231,10 @@ (define_mode_attr bitimm
> (V4SI "uimm5")
> (V2DI "uimm6")])
>
> +;; The index of sign bit in FP vector elements.
> +(define_mode_attr elmsgnbit [(V2DF "63") (V4DF "63")
> + (V4SF "31") (V8SF "31")])
> +
> (define_expand "vec_init<mode><unitmode>"
> [(match_operand:MSA 0 "register_operand")
> (match_operand:MSA 1 "")]
> @@ -597,9 +601,9 @@ (define_expand "abs<mode>2"
> })
>
> (define_expand "neg<mode>2"
> - [(set (match_operand:MSA 0 "register_operand")
> - (minus:MSA (match_dup 2)
> - (match_operand:MSA 1 "register_operand")))]
> + [(set (match_operand:IMSA 0 "register_operand")
> + (minus:IMSA (match_dup 2)
> + (match_operand:IMSA 1 "register_operand")))]
> "ISA_HAS_MSA"
> {
> rtx reg = gen_reg_rtx (<MODE>mode);
> @@ -607,6 +611,14 @@ (define_expand "neg<mode>2"
> operands[2] = reg;
> })
>
> +(define_insn "neg<mode>2"
> + [(set (match_operand:FMSA 0 "register_operand" "=f")
> + (neg (match_operand:FMSA 1 "register_operand" "f")))]
> + "ISA_HAS_MSA"
> + "bnegi.<msafmt>\t%w0,%w1,<elmsgnbit>"
> + [(set_attr "type" "simd_bit")
> + (set_attr "mode" "<MODE>")])
> +
> (define_expand "msa_ldi<mode>"
> [(match_operand:IMSA 0 "register_operand")
> (match_operand 1 "const_imm10_operand")]
> --
> 2.43.0
>
