Re: [PATCH 07/21] ARC: math soft float support
On Thu, 20 Dec 2018, Vineet Gupta wrote: > I'm still ramping up on hard-float, so pardon some of my naivety. It seems the > function calling convention is no different for soft-float vs. hard-float. We > have > a single register file (hard FP instructions inherently use an additional > accumulator but that isn't really passed around so doesn't affect calling > convention). Other than that SP values go normally in a reg, DP go in reg pair > just as any 64bit value. If you have only a single register file and the same calling convention - and all struct layouts etc. are also the same - then indeed that would be a single ABI (meaning that you only need one dynamic linker name for ARC rather than two, if you only support one endianness). (On architectures with separate register files, jmp_buf, ucontext etc. might sometimes differ between hard and soft float, although often the space is still there in the soft-float case, just not used.) The ARM and RISC-V cases are ones where there are separate hard-float and soft-float calling conventions - but *also* support for using hardware floating point with the soft-float calling convention. If you do have a single ABI, that indicates having bits/fenv.h contents unconditional (because a soft-float compilation might legitimately end up linking with a hard-float libm) - and thus indeed needing the internal headers to disable certain math tests for soft-float. fpu_control.h contents would still be conditional, however. -- Joseph S. Myers jos...@codesourcery.com ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
Re: [PATCH 07/21] ARC: math soft float support
On 12/18/18 3:23 PM, Joseph Myers wrote:
> On Tue, 18 Dec 2018, Vineet Gupta wrote:
>
>> +#if defined(__ARC_FPU_SP__) || defined(__ARC_FPU_DP__)
>
> Missing spaces before '(' (should have such spaces in most cases between
> an identifier or keyword and '(' - calls to "defined", calls to functions,
> calls to macros, __attribute__, etc. - except for a few cases of calls to
> macros such as ElfW where the result is logically used like an
> identifier).
OK, I removed the parens in this case (update: removed the guard altogether, see
below).
>> +/* In the soft-float case, only rounding to nearest is supported, with
>> + no exceptions. */
>
> To confirm: hard-float and soft-float are always different ABIs; you don't
> support hard-float compilation using the soft-float function calling ABI
> (like is supported for ARM and RISC-V, for example)?
I'm still ramping up on hard-float, so pardon some of my naivety. It seems the
function calling convention is no different for soft-float vs. hard-float. We
have
a single register file (hard FP instructions inherently use an additional
accumulator but that isn't really passed around so doesn't affect calling
convention). Other than that SP values go normally in a reg, DP go in reg pair
just as any 64bit value.
OTOH, the ARC libgcc float emulation code seems likely to be limited in terms of
rounding modes supported etc (the current code is dense math implemented in ARC
assembly (really not my cup of coffee) so I couldn't be sure :-(
At any rate, assuming it did limit the rounding modes etc, does that also lend
into the ABI we are talking about here ? Likely not.
> (If you support
> hard-float compilation with the soft-float ABI, it would be problematic to
> have different FE_TONEAREST values in the two cases - ARM and RISC-V both
> define all the FE_* macros independently of whether hard or soft float is
> used, because they support that case.)
I'd much rather have them be the same. The fenv.h I started with didn't
distinguish these (well it only had 1 rounding mode: FE_TONEAREST so was bogus
at
best). When I revered it up, I added the various modes etc w/o the header guard
and ho behold all the math tests started failing. My knee jerk response was to
segregate them which likely papered over the issue.
>> diff --git a/sysdeps/arc/math_private.h b/sysdeps/arc/math_private.h
>
> This file should not be needed now.
Ok deleted.
>> diff --git a/sysdeps/arc/nofpu/math-tests-exception.h
>> b/sysdeps/arc/nofpu/math-tests-exception.h
>
> This file does nothing (the name is wrong, the name actually used is
> math-tests-exceptions.h). And it should not be needed unless you support
> hard-float compilation with the soft-float ABI (and thus define all the
> FE_* names in bits/fenv.h even for soft-float).
File renamed and retained.
>> diff --git a/sysdeps/arc/nofpu/math-tests-rounding.h
>> b/sysdeps/arc/nofpu/math-tests-rounding.h
>
> Again, not needed unless hard-float compilation with the soft-float ABI is
> supported and bits/fenv.h has corresponding contents.
ditto !
Now trying a rebuilt with these changes !
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Re: [PATCH 07/21] ARC: math soft float support
On 12/18/18 4:01 PM, Joseph Myers wrote:
> On Tue, 18 Dec 2018, Joseph Myers wrote:
>
>> On Tue, 18 Dec 2018, Vineet Gupta wrote:
>>
>>> +#if defined(__ARC_FPU_SP__) || defined(__ARC_FPU_DP__)
>> Missing spaces before '(' (should have such spaces in most cases between
>> an identifier or keyword and '(' - calls to "defined", calls to functions,
>> calls to macros, __attribute__, etc. - except for a few cases of calls to
>> macros such as ElfW where the result is logically used like an
>> identifier).
> Or, of course, just omit the parentheses in the "defined" case, which is
> very common for calls to "defined" in glibc.
>
> (Function-like macro definitions are a case where you *can't* have the
> space because the syntax of C requires no space between the name of the
> macro being defined and the '(' before the list of argument names.)
Ok, done !
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Re: [PATCH 07/21] ARC: math soft float support
On Tue, 18 Dec 2018, Joseph Myers wrote:
> On Tue, 18 Dec 2018, Vineet Gupta wrote:
>
> > +#if defined(__ARC_FPU_SP__) || defined(__ARC_FPU_DP__)
>
> Missing spaces before '(' (should have such spaces in most cases between
> an identifier or keyword and '(' - calls to "defined", calls to functions,
> calls to macros, __attribute__, etc. - except for a few cases of calls to
> macros such as ElfW where the result is logically used like an
> identifier).
Or, of course, just omit the parentheses in the "defined" case, which is
very common for calls to "defined" in glibc.
(Function-like macro definitions are a case where you *can't* have the
space because the syntax of C requires no space between the name of the
macro being defined and the '(' before the list of argument names.)
--
Joseph S. Myers
jos...@codesourcery.com
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Re: [PATCH 07/21] ARC: math soft float support
On Tue, 18 Dec 2018, Vineet Gupta wrote:
> +#if defined(__ARC_FPU_SP__) || defined(__ARC_FPU_DP__)
Missing spaces before '(' (should have such spaces in most cases between
an identifier or keyword and '(' - calls to "defined", calls to functions,
calls to macros, __attribute__, etc. - except for a few cases of calls to
macros such as ElfW where the result is logically used like an
identifier).
> +/* In the soft-float case, only rounding to nearest is supported, with
> + no exceptions. */
To confirm: hard-float and soft-float are always different ABIs; you don't
support hard-float compilation using the soft-float function calling ABI
(like is supported for ARM and RISC-V, for example)? (If you support
hard-float compilation with the soft-float ABI, it would be problematic to
have different FE_TONEAREST values in the two cases - ARM and RISC-V both
define all the FE_* macros independently of whether hard or soft float is
used, because they support that case.)
> diff --git a/sysdeps/arc/math_private.h b/sysdeps/arc/math_private.h
This file should not be needed now.
> diff --git a/sysdeps/arc/nofpu/math-tests-exception.h
> b/sysdeps/arc/nofpu/math-tests-exception.h
This file does nothing (the name is wrong, the name actually used is
math-tests-exceptions.h). And it should not be needed unless you support
hard-float compilation with the soft-float ABI (and thus define all the
FE_* names in bits/fenv.h even for soft-float).
> diff --git a/sysdeps/arc/nofpu/math-tests-rounding.h
> b/sysdeps/arc/nofpu/math-tests-rounding.h
Again, not needed unless hard-float compilation with the soft-float ABI is
supported and bits/fenv.h has corresponding contents.
--
Joseph S. Myers
jos...@codesourcery.com
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