Re: [Patch, ARM] Relax the restrictions on REG_SP under Thumb mode on ARMv8-A

[Ramana Radhakrishnan <ramana dot gcc at googlemail dot com>]

On Fri, May 26, 2017 at 2:34 PM, Jiong Wang <jiong.wang@foss.arm.com> wrote:
> Hi,
>
>   For Thumb mode, since ARMv8-A, REG_SP is allowed in most of the places in
> Rd/Rt/Rt2 etc while it was disallowed before ARMv8-A, and was rejected
> through
> the "reject_bad_reg" macro and several scattered checks.
>
>   This patch only rejects REG_SP in "reject_bad_reg" and several related
> places
> for legacy architectures before ARMv8-A. I have checked those affected
> instructions
> , all of them qualify such relaxations.
>
>   Testcases adjusted accordingly.
>     * ld-sp-warn.d was written without .arch and without -march options
> passed.
>       By default it assumes all architectures, so I deleted the REG_SP
> warning
>       on ldrsb as it's supported on ARMv8-A.  There are actually quite a few
>       seperate tests on other architectures, for example ld-sp-warn-v7.l
> etc.,
>       so there the test for ldrsb on legacy architectures are still covered.
>     * sp-pc-validations-bad-t has been extended to armv8-a.
>     * strex-bad-t.d restricted on armv7-a.
>     * Some new tests for REG_SP used as Rd/Rt etc added in
> sp-usage-thumb2-relax*.
>
>   OK for master?
>

Since this affects release branches and I've got an internal user
complaining about this - can we backport this to the binutils 2.28 and
binutils 2.29 branches ?

Ramana

>   Thanks.
>
> gas/
> 2017-05-25  Jiong Wang  <jiong.wang@arm.com>
>
>         * config/tc-arm.c (reject_bad_reg): Allow REG_SP on ARMv8-A.
>         (parse_operands): Allow REG_SP for OP_oRRnpcsp and OP_RRnpcsp on
>         ARMv8-A.
>         (do_co_reg): Allow REG_SP for Rd on ARMv8-A.
>         (do_t_add_sub): Likewise.
>         (do_t_mov_cmp): Likewise.
>         (do_t_tb): Likewise.
>         * testsuite/gas/arm/ld-sp-warn.l: Delete the warning on REG_SP as Rt
> for
>         ldrsb.
>         * testsuite/gas/arm/sp-pc-validations-bad-t-v8a.d: New test.
>         * testsuite/gas/arm/sp-pc-validations-bad-t-v8a.l: New test.
>         * testsuite/gas/arm/sp-pc-validations-bad-t.d: Specifies
> -march=armv7-a.
>         * testsuite/gas/arm/sp-pc-validations-bad-t.s: Remove ".arch
> armv7-a".
>         * testsuite/gas/arm/sp-usage-thumb2-relax-on-v7.d: New test.
>         * testsuite/gas/arm/sp-usage-thumb2-relax-on-v7.l: New test.
>         * testsuite/gas/arm/sp-usage-thumb2-relax-on-v8.d: New test.
>         * testsuite/gas/arm/sp-usage-thumb2-relax.s: New test.
>         * testsuite/gas/arm/strex-bad-t.d: Specifies -march=armv7-a.
>