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Re: [PATCH, libgcc/ARM 1/6] Fix Thumb-1 only == ARMv6-M & Thumb-2 only == ARMv7-M assumptions
- From: Ramana Radhakrishnan <ramana dot gcc at googlemail dot com>
- To: Thomas Preudhomme <thomas dot preudhomme at foss dot arm dot com>
- Cc: gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 6 Jul 2016 17:20:04 +0100
- Subject: Re: [PATCH, libgcc/ARM 1/6] Fix Thumb-1 only == ARMv6-M & Thumb-2 only == ARMv7-M assumptions
- Authentication-results: sourceware.org; auth=none
- References: <001301d14d1b$27cc4810$7764d830$@foss.arm.com> <CAJA7tRbYj-uyPwvTFHcAB5L8Tm3zQHRxofi7wcwU=TVeqhafGQ@mail.gmail.com> <4707964.lx3ShB1mLb@e108577-lin>
On Mon, Jun 27, 2016 at 5:51 PM, Thomas Preudhomme
<thomas.preudhomme@foss.arm.com> wrote:
> Hi Ramana,
>
> On Wednesday 01 June 2016 10:00:52 Ramana Radhakrishnan wrote:
>>
>> From here down to ....
>>
>> > -#if ((__ARM_ARCH__ > 5) && !defined(__ARM_ARCH_6M__)) \
>> > - || defined(__ARM_ARCH_5E__) || defined(__ARM_ARCH_5TE__) \
>> > - || defined(__ARM_ARCH_5TEJ__)
>> > -#define HAVE_ARM_CLZ 1
>> > -#endif
>> > -
>> >
>> > #ifdef L_clzsi2
>> >
>> > -#if defined(__ARM_ARCH_6M__)
>> > +#if !__ARM_ARCH_ISA_ARM && __ARM_ARCH_ISA_THUMB == 1
>> >
>> > FUNC_START clzsi2
>> >
>> > mov r1, #28
>> > mov r3, #1
>> >
>> > @@ -1544,7 +1538,7 @@ FUNC_START clzsi2
>> >
>> > FUNC_END clzsi2
>> >
>> > #else
>> > ARM_FUNC_START clzsi2
>> >
>> > -# if defined(HAVE_ARM_CLZ)
>> > +# if defined(__ARM_FEATURE_CLZ)
>> >
>> > clz r0, r0
>> > RET
>> >
>> > # else
>> >
>> > @@ -1568,15 +1562,15 @@ ARM_FUNC_START clzsi2
>> >
>> > .align 2
>> > 1:
>> > .byte 4, 3, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0
>> >
>> > -# endif /* !HAVE_ARM_CLZ */
>> > +# endif /* !__ARM_FEATURE_CLZ */
>> >
>> > FUNC_END clzsi2
>> >
>> > #endif
>> > #endif /* L_clzsi2 */
>> >
>> > #ifdef L_clzdi2
>> >
>> > -#if !defined(HAVE_ARM_CLZ)
>> > +#if !defined(__ARM_FEATURE_CLZ)
>>
>> here should be it's own little patchlet and can go in separately.
>
> The patch in attachment changes the CLZ availability check in libgcc to test
> ISA supported and architecture version rather than encode a specific list of
> architectures. __ARM_FEATURE_CLZ is not used because its value depends on what
> mode the user is targeting but only the architecture support matters in this
> case. Indeed, the code using CLZ is written in assembler and uses mnemonics
> available both in ARM and Thumb mode so only CLZ availability in one of the
> mode matters.
>
> This change was split out from [PATCH, GCC, ARM 1/7] Fix Thumb-1 only ==
> ARMv6-M & Thumb-2 only == ARMv7-M assumptions.
>
> ChangeLog entry is as follows:
>
> *** libgcc/ChangeLog ***
>
> 2016-06-16 Thomas Preud'homme <thomas.preudhomme@arm.com>
>
> * config/arm/lib1funcs.S (HAVE_ARM_CLZ): Define for ARMv6* or later
> and ARMv5t* rather than for a fixed list of architectures.
>
> Looking for code generation change accross a number of combinations of ISAs
> (ARM/Thumb), optimization levels (Os/O2), and architectures (armv4, armv4t,
> armv5, armv5t, armv5te, armv6, armv6j, armv6k, armv6s-m, armv6kz, armv6t2,
> armv6z, armv6zk, armv7, armv7-a, armv7e-m, armv7-m, armv7-r, armv7ve, armv8-a,
> armv8-a+crc, iwmmxt and iwmmxt2) shows that only ARMv5T is impacted (uses CLZ
> now). This is expected because currently HAVE_ARM_CLZ is not defined for this
> architecture while the ARMv7-a/ARMv7-R Architecture Reference Manual [1]
> states that all ARMv5T* architectures have CLZ. ARMv5E should also be impacted
> (not using CLZ anymore) but testing it is difficult since current binutils does
> not support ARMv5E.
>
> [1] Document ARM DDI0406C in http://infocenter.arm.com
>
> Best regards,
>
> Thomas
OK.
Ramana