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Re: [PING][Patch] Add support for IEEE-conformant versions of scalar fmin* and fmax*
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: David Sherwood <david dot sherwood at arm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 17 Aug 2015 15:56:56 +0200
- Subject: Re: [PING][Patch] Add support for IEEE-conformant versions of scalar fmin* and fmax*
- Authentication-results: sourceware.org; auth=none
- References: <000001d0d5b0$5da4dbb0$18ee9310$ at arm dot com> <CAFiYyc1bgWwdV4PRLBuUv3yC0X-k5gJVuyyV9V7Vrz3Lte+wZw at mail dot gmail dot com> <000001d0d8cf$2fb42770$8f1c7650$ at arm dot com>
On Mon, Aug 17, 2015 at 11:29 AM, David Sherwood <david.sherwood@arm.com> wrote:
> Hi Richard,
>
> Thanks for the reply. I'd chosen to add new expressions as this seemed more
> consistent with the existing MAX_EXPR and MIN_EXPR tree codes. In addition it
> would seem to provide more opportunities for optimisation than a target-specific
> builtin implementation would. I accept that optimisation opportunities will
> be more limited for strict math compilation, but that it was still worth having
> them. Also, if we did map it to builtins then the scalar version would go
> through the optabs and the vector version would go through the target's builtin
> expansion, which doesn't seem very consistent.
On another note ISTR you can't associate STRICT_MIN/MAX_EXPR and thus
you can't vectorize anyway? (strict IEEE behavior is about NaNs, correct?)
Richard.
> Regards,
> David.
>
>> -----Original Message-----
>> From: Richard Biener [mailto:richard.guenther@gmail.com]
>> Sent: 13 August 2015 12:10
>> To: David Sherwood
>> Cc: GCC Patches
>> Subject: Re: [PING][Patch] Add support for IEEE-conformant versions of scalar fmin* and fmax*
>>
>> On Thu, Aug 13, 2015 at 12:11 PM, David Sherwood <david.sherwood@arm.com> wrote:
>> > Hi,
>> >
>> > Sorry to bother people again. Is this OK to go now?
>>
>> Hmm, why don't you go the vectorized function call path for this,
>> implementing the builtin_vectorized_function target hook?
>>
>> Richard.
>>
>> > Thanks!
>> > David.
>> >
>> >> >
>> >> > > On Mon, 29 Jun 2015, David Sherwood wrote:
>> >> > >
>> >> > > > Hi,
>> >> > > >
>> >> > > > I have added new STRICT_MAX_EXPR and STRICT_MIN_EXPR expressions to support the
>> >> > > > IEEE versions of fmin and fmax. This is done by recognising the math library
>> >> > > > "fmax" and "fmin" builtin functions in a similar way to how this is done for
>> >> > > > -ffast-math. This also allows us to vectorise the IEEE max/min functions for
>> >> > > > targets that support it, for example aarch64/aarch32.
>> >> > >
>> >> > > This patch is missing documentation. You need to document the new insn
>> >> > > patterns in md.texi and the new tree codes in generic.texi.
>> >> >
>> >> > Hi, I've uploaded a new patch with the documentation. Hope this is ok.
>> >>
>> >> In various places where you refer to one operand being NaN, I think you
>> >> mean one operand being a *quiet* NaN (if one is a signaling NaN - only
>> >> supported by GCC if -fsignaling-nans - the IEEE minNum and maxNum
>> >> operations raise "invalid" and return a quiet NaN).
>> >
>> > Hi, I have a new patch that hopefully addresses the documentation issues.
>> >
>> > Thanks,
>> > David.
>> >
>> > ChangeLog:
>> >
>> > 2015-07-15 David Sherwood <david.sherwood@arm.com>
>> >
>> > gcc/
>> > * builtins.c (integer_valued_real_p): Add STRICT_MIN_EXPR and
>> > STRICT_MAX_EXPR.
>> > (fold_builtin_fmin_fmax): For strict math, convert builting fmin and
>> > fmax to STRICT_MIN_EXPR and STRICT_MIN_EXPR, respectively.
>> > * expr.c (expand_expr_real_2): Add STRICT_MIN_EXPR and STRICT_MAX_EXPR.
>> > * fold-const.c (const_binop): Likewise.
>> > (fold_binary_loc, tree_binary_nonnegative_warnv_p): Likewise.
>> > (tree_binary_nonzero_warnv_p): Likewise.
>> > * optabs.h (strict_minmax_support): Declare.
>> > * optabs.def: Add new optabs strict_max_optab/strict_min_optab.
>> > * optabs.c (optab_for_tree_code): Return new optabs for STRICT_MIN_EXPR
>> > and STRICT_MAX_EXPR.
>> > (strict_minmax_support): New function.
>> > * real.c (real_arithmetic): Add STRICT_MIN_EXPR and STRICT_MAX_EXPR.
>> > * tree.def: Likewise.
>> > * tree.c (associative_tree_code, commutative_tree_code): Likewise.
>> > * tree-cfg.c (verify_expr): Likewise.
>> > (verify_gimple_assign_binary): Likewise.
>> > * tree-inline.c (estimate_operator_cost): Likewise.
>> > * tree-pretty-print.c (dump_generic_node, op_code_prio): Likewise.
>> > (op_symbol_code): Likewise.
>> > gcc/config:
>> > * aarch64/aarch64.md: New pattern.
>> > * aarch64/aarch64-simd.md: Likewise.
>> > * aarch64/iterators.md: New unspecs, iterators.
>> > * arm/iterators.md: New iterators.
>> > * arm/unspecs.md: New unspecs.
>> > * arm/neon.md: New pattern.
>> > * arm/vfp.md: Likewise.
>> > gcc/doc:
>> > * generic.texi: Add STRICT_MAX_EXPR and STRICT_MIN_EXPR.
>> > * md.texi: Add strict_min and strict_max patterns.
>> > gcc/testsuite
>> > * gcc.target/aarch64/maxmin_strict.c: New test.
>> > * gcc.target/arm/maxmin_strict.c: New test.
>
>
>