On Tue, Aug 13, 2019 at 2:33 PM Richard Biener <rguent...@suse.de> wrote:
>
>
> The following splits out the change that makes the live-range split /
> mode change copy pseudos vector mode pseudos. I've tried reproducing
> the issue I faced with SImode chains but failed likely because we're
> never using simple moves in the end while for SImode we can end up
> with
>
> (set (subreg:V4SI (reg:SI 42) 0) (subreg:V4SI (reg:SI 41) 0))
>
> which we happily propagate out. So pursuing this patch independently
> doesn't make much sense. Still the main change is in
> dimode_scalar_chain::make_vector_copies where 'vreg' is now V2DImode
> instead of DImode and the change to emit_move_insn (vreg, tmp)
> hints at the change done to the above problematic insn.
>
> The rest of the changes deal with some regs already being in
> the appropriate vector mode.
>
> I realize I might have avoided my original issue by emitting not
> the above reg-reg move but
>
> (set (subreg:V4SI (reg:SI 42) 0)
> (vec_merge:V4SI
> (vec_duplicate:V4SI (reg:SI 41))
> (const_vec [0 0 0 0])
> (const_1)))
>
> but I didn't try (the full patch contained a testcase for the
> issue). Still it seems odd to use DImode pseudos when all uses
> are wrapped in (subreg:V2DI ...).
It looks to me that the above is the way to go. make_vector_copies
creates a scalar pseudo, and all other support functions expect a
scalar that will be processed with "replace_with_subreg". I think that
the safest way is to emit the code above for SImode for the
problematic move insn, and
> + emit_move_insn (gen_rtx_SUBREG (V2DImode, vreg 0),
> + gen_rtx_VEC_MERGE (V2DImode,
> + gen_rtx_VEC_DUPLICATE
> (V2DImode,
> + tmp),
> + CONST0_RTX (V2DImode),
> + GEN_INT (HOST_WIDE_INT_1U)));
for DImode. This way, you won't need other changes (conditional
generation of SUBREGs), the above should be enough.
Oh, and don't use emit_move_insn, emit insn with gen_rtx_SET
(gen_rtx_SUBREG (...)) should do the trick.
Uros.
> As (unrelated) change I propose to error with fatal_insn_not_found
> in case recog doesn't recognize the altered insns which make it
> easier to spot errors early.
>
> Bootstrap / regtest running on x86_64-unknown-linux-gnu ontop of [1/2], OK
> for trunk if that succeeds?
>
> Thanks,
> Richard.
>
> 2019-08-13 Richard Biener <rguent...@suse.de>
>
> * config/i386/i386-features.c
> (dimode_scalar_chain::replace_with_subreg): Elide the subreg if the
> reg is already vector.
> (dimode_scalar_chain::convert_op): Likewise.
> (dimode_scalar_chain::make_vector_copies): Use a vector-mode pseudo as
> destination to avoid later passes copy-propagating it out.
> (dimode_chain::convert_insn): Convert the source of a
> memory op in case it is not of the appropriate scalar mode.
> Raise fatal_insn_not_found if the converted insn is not recognized.
>
> Index: gcc/config/i386/i386-features.c
> ===================================================================
> --- gcc/config/i386/i386-features.c (revision 274328)
> +++ gcc/config/i386/i386-features.c (working copy)
> @@ -573,7 +573,8 @@ rtx
> dimode_scalar_chain::replace_with_subreg (rtx x, rtx reg, rtx new_reg)
> {
> if (x == reg)
> - return gen_rtx_SUBREG (V2DImode, new_reg, 0);
> + return (GET_MODE (new_reg) == V2DImode
> + ? new_reg : gen_rtx_SUBREG (V2DImode, new_reg, 0));
>
> const char *fmt = GET_RTX_FORMAT (GET_CODE (x));
> int i, j;
> @@ -627,7 +628,7 @@ void
> dimode_scalar_chain::make_vector_copies (unsigned regno)
> {
> rtx reg = regno_reg_rtx[regno];
> - rtx vreg = gen_reg_rtx (DImode);
> + rtx vreg = gen_reg_rtx (V2DImode);
> df_ref ref;
>
> for (ref = DF_REG_DEF_CHAIN (regno); ref; ref = DF_REF_NEXT_REG (ref))
> @@ -641,7 +642,12 @@ dimode_scalar_chain::make_vector_copies
> gen_rtx_SUBREG (SImode, reg, 0));
> emit_move_insn (adjust_address (tmp, SImode, 4),
> gen_rtx_SUBREG (SImode, reg, 4));
> - emit_move_insn (vreg, tmp);
> + emit_move_insn (vreg,
> + gen_rtx_VEC_MERGE (V2DImode,
> + gen_rtx_VEC_DUPLICATE
> (V2DImode,
> + tmp),
> + CONST0_RTX (V2DImode),
> + GEN_INT (HOST_WIDE_INT_1U)));
> }
> else if (TARGET_SSE4_1)
> {
> @@ -841,7 +847,8 @@ dimode_scalar_chain::convert_op (rtx *op
> gcc_assert (!DF_REF_CHAIN (ref));
> break;
> }
> - *op = gen_rtx_SUBREG (V2DImode, *op, 0);
> + if (GET_MODE (*op) != V2DImode)
> + *op = gen_rtx_SUBREG (V2DImode, *op, 0);
> }
> else if (CONST_INT_P (*op))
> {
> @@ -931,6 +938,8 @@ dimode_scalar_chain::convert_insn (rtx_i
> case MEM:
> if (!REG_P (dst))
> convert_op (&src, insn);
> + else if (GET_MODE (src) != DImode)
> + src = gen_rtx_SUBREG (DImode, src, 0);
> break;
>
> case REG:
> @@ -977,7 +986,9 @@ dimode_scalar_chain::convert_insn (rtx_i
> PATTERN (insn) = def_set;
>
> INSN_CODE (insn) = -1;
> - recog_memoized (insn);
> + int patt = recog_memoized (insn);
> + if (patt == -1)
> + fatal_insn_not_found (insn);
> df_insn_rescan (insn);
> }
>
