[PATCH 3/5] amdgcn: Add clrsbsi2/clrsbdi2 implementation
Andrew Stubbs
ams@codesourcery.com
Fri Jun 18 15:01:55 GMT 2021
On 18/06/2021 15:19, Julian Brown wrote:
> This patch adds an open-coded implementation of the clrsb<mode>2
> (count leading redundant sign bit) standard names using the GCN flbit_i*
> instructions for SImode and DImode. Those don't count exactly as we need,
> so we need a couple of other instructions to fix up the result afterwards.
>
> These patterns are lost from libgcc if we build it for DImode/TImode
> rather than SImode/DImode, a change we make in a later patch in this
> series.
>
> I can probably self-approve this, but I'll give Andrew Stubbs a chance
> to comment.
>
> Thanks,
>
> Julian
>
> 2021-06-18 Julian Brown <julian@codesourcery.com>
>
> gcc/
> * config/gcn/gcn.md (UNSPEC_FLBIT_INT): New unspec constant.
> (s_mnemonic): Add clrsb.
> (gcn_flbit<mode>_int): Add insn pattern for SImode/DImode.
> (clrsb<mode>2): Add expander for SImode/DImode.
> ---
> gcc/config/gcn/gcn.md | 40 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 38 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/gcn/gcn.md b/gcc/config/gcn/gcn.md
> index 70655ca4b8b..0fa7f86702e 100644
> --- a/gcc/config/gcn/gcn.md
> +++ b/gcc/config/gcn/gcn.md
> @@ -81,7 +81,8 @@
> UNSPEC_MOV_FROM_LANE63
> UNSPEC_GATHER
> UNSPEC_SCATTER
> - UNSPEC_RCP])
> + UNSPEC_RCP
> + UNSPEC_FLBIT_INT])
>
> ;; }}}
> ;; {{{ Attributes
> @@ -338,7 +339,8 @@
> [(not "not%b")
> (popcount "bcnt1_i32%b")
> (clz "flbit_i32%b")
> - (ctz "ff1_i32%b")])
> + (ctz "ff1_i32%b")
> + (clrsb "flbit_i32%i")])
>
> (define_code_attr revmnemonic
> [(minus "subrev%i")
> @@ -1509,6 +1511,40 @@
> [(set_attr "type" "sop1")
> (set_attr "length" "4,8")])
>
> +(define_insn "gcn_flbit<mode>_int"
> + [(set (match_operand:SI 0 "register_operand" "=Sg,Sg")
> + (unspec:SI [(match_operand:SIDI 1 "gcn_alu_operand" "SgA, B")]
> + UNSPEC_FLBIT_INT))]
> + ""
> + {
> + if (<MODE>mode == SImode)
> + return "s_flbit_i32\t%0, %1";
> + else
> + return "s_flbit_i32_i64\t%0, %1";
> + }
> + [(set_attr "type" "sop1")
> + (set_attr "length" "4,8")])
> +
> +(define_expand "clrsb<mode>2"
> + [(set (match_operand:SI 0 "register_operand" "")
> + (clrsb:SI (match_operand:SIDI 1 "gcn_alu_operand" "")))]
> + ""
> + {
> + rtx tmp = gen_reg_rtx (SImode);
> + /* FLBIT_I* counts sign or zero bits at the most-significant end of the
> + input register (and returns -1 for 0/-1 inputs). We want the number of
> + *redundant* bits (i.e. that value minus one), and an answer of 31/63 for
> + 0/-1 inputs. We can do that in three instructions... */
> + emit_insn (gen_gcn_flbit<mode>_int (tmp, operands[1]));
> + emit_insn (gen_uminsi3 (tmp, tmp,
> + gen_int_mode (GET_MODE_BITSIZE (<MODE>mode),
> + SImode)));
> + /* If we put this last, it can potentially be folded into a subsequent
> + arithmetic operation. */
> + emit_insn (gen_subsi3 (operands[0], tmp, const1_rtx));
> + DONE;
> + })
> +
> ;; }}}
> ;; {{{ ALU: generic 32-bit binop
>
>
OK.
Andrew
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