RE: [GCC][PATCH][mid-end] Optimize x * copysign (1.0, y) [Patch (1/2)]

[Tamar Christina <Tamar dot Christina at arm dot com>]

> I see.  But the implementation challenge is that this interacts badly with SSA
> coalescing done before this and thus should really happen on GIMPLE before
> that.
> 
> And yes, I also like to see more of this, it's basically doing some instruction
> selection on (late) GIMPLE.  Ideally we'd be able to generate an expand.pd
> match.pd variant from the machine description (named) define_insns,
> creating IFNs that we know how to expand.

Fair enough, Just to check I understood correctly.

It should be a match.pd rule that uses a match predicate, so expand in gimple-match.c.
but don't do this if the target doesn't have the xorsign optab and don't do it if honouring SNAN.

I'll make the changes then.
Thanks,
Tamar

> 
> Think of a combine pass combining GIMPLE stmts to (recognized) RTL insn
> (sequences).  Until RTL expansion the RTL insn (sequence) would be
> represented by an internal function call (or alternatively for multi-output
> cases an GIMPLE ASM with enumerated asm text).
> 
> Richard.
> 
> > > Thanks,
> > > Richard.
> > >
> > > >
> > > > gcc/
> > > > 2017-07-10  Tamar Christina  <tamar.christina@arm.com>
> > > > 	    Andrew Pinski <pinskia@gmail.com>
> > > >
> > > > 	PR middle-end/19706
> > > > 	* expr.c (is_copysign_call_with_1): New.
> > > > 	(maybe_expand_mult_copysign): Likewise.
> > > > 	(expand_expr_real_2): Expand copysign.
> > > > 	* optabs.def (xorsign_optab): New.
> > > >
> > > > ________________________________________
> > > > From: Andrew Pinski <pinskia@gmail.com>
> > > > Sent: Monday, July 10, 2017 12:21:29 AM
> > > > To: Tamar Christina
> > > > Cc: GCC Patches; nd; law@redhat.com; ian@airs.com;
> > > > rguenther@suse.de
> > > > Subject: Re: [GCC][PATCH][mid-end] Optimize x * copysign (1.0, y)
> > > > [Patch (1/2)]
> > > >
> > > > On Mon, Jun 12, 2017 at 12:56 AM, Tamar Christina
> > > > <Tamar.Christina@arm.com> wrote:
> > > > > Hi All,
> > > > >
> > > > > this patch implements a optimization rewriting
> > > > >
> > > > > x * copysign (1.0, y) and
> > > > > x * copysign (-1.0, y)
> > > > >
> > > > > to:
> > > > >
> > > > > x ^ (y & (1 << sign_bit_position))
> > > > >
> > > > > This is done by creating a special builtin during matching and
> > > > > generate the appropriate instructions during expand. This new
> > > > > builtin is
> > > called XORSIGN.
> > > > >
> > > > > The expansion of xorsign depends on if the backend has an
> > > > > appropriate optab available. If this is not the case then we use
> > > > > a modified version of the existing copysign which does not take
> > > > > the abs
> > > value of the first argument as a fall back.
> > > > >
> > > > > This patch is a revival of a previous patch
> > > > > https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00069.html
> > > > >
> > > > > Bootstrapped on both aarch64-none-linux-gnu and x86_64 with no
> > > issues.
> > > > > Regression done on aarch64-none-linux-gnu and no regressions.
> > > >
> > > >
> > > > Note this is also PR 19706.
> > > >
> > > > Thanks,
> > > > Andrew
> > > >
> > > > >
> > > > > Ok for trunk?
> > > > >
> > > > > gcc/
> > > > > 2017-06-07  Tamar Christina  <tamar.christina@arm.com>
> > > > >
> > > > >         * builtins.def (BUILT_IN_XORSIGN, BUILT_IN_XORSIGNF): New.
> > > > >         (BUILT_IN_XORSIGNL, BUILT_IN_XORSIGN_FLOAT_NX):
> Likewise.
> > > > >         * match.pd (mult (COPYSIGN:s real_onep @0) @1): New
> simplifier.
> > > > >         (mult (COPYSIGN:s real_mus_onep @0) @1): Likewise.
> > > > >         (copysigns @0 (negate @1)): Likewise.
> > > > >         * builtins.c (expand_builtin_copysign): Promoted local to
> argument.
> > > > >         (expand_builtin): Added CASE_FLT_FN_FLOATN_NX
> > > (BUILT_IN_XORSIGN) and
> > > > >         CASE_FLT_FN (BUILT_IN_XORSIGN).
> > > > >         (BUILT_IN_COPYSIGN): Updated function call.
> > > > >         * optabs.h (expand_copysign): New bool.
> > > > >         (expand_xorsign): New.
> > > > >         * optabs.def (xorsign_optab): New.
> > > > >         * optabs.c (expand_copysign): New parameter.
> > > > >         * fortran/f95-lang.c (xorsignl, xorsign, xorsignf): New.
> > > > >         * fortran/mathbuiltins.def (XORSIGN): New.
> > > > >
> > > > > gcc/testsuite/
> > > > > 2017-06-07  Tamar Christina  <tamar.christina@arm.com>
> > > > >
> > > > >         * gcc.dg/tree-ssa/xorsign.c: New.
> > > > >         * gcc.dg/xorsign_exec.c: New.
> > > > >         * gcc.dg/vec-xorsign_exec.c: New.
> > > > >         * gcc.dg/tree-ssa/reassoc-39.c (f2, f3): Updated constant to 2.
> > > >
> > >
> > > --
> > > Richard Biener <rguenther@suse.de>
> > > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham
> > > Norton, HRB 21284 (AG Nuernberg)
> >
> >
> 
> --
> Richard Biener <rguenther@suse.de>
> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton,
> HRB 21284 (AG Nuernberg)