linux-kernel - Re: [PATCH 2/7] ARM: LTO: avoid THUMB2

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Message-ID: <CAK8P3a0VR1bkwdQ+Th6mPVVV_t5YoyqGPOAiWmtg8kVnjUha-g@mail.gmail.com>
Date:   Wed, 21 Feb 2018 12:48:42 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] ARM: LTO: avoid THUMB2_KERNEL+LTO

On Wed, Feb 21, 2018 at 4:12 AM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> On Tue, 20 Feb 2018, Arnd Bergmann wrote:
>
>> Trying to build an LTO-Enabled kernel with Thumb2 instructions failed
>> horribly for me, with an endless output of things like
>>
>> ccVnNycO.s:2665: Error: thumb conditional instruction should be in IT block -- `bxne lr'
>> ccVnNycO.s:7128: Error: thumb conditional instruction should be in IT block -- `strexeq r5,r2,[r3]'
>> ccVnNycO.s:7258: Error: thumb conditional instruction should be in IT block -- `strexeq lr,r0,[r3]'
>> ccVnNycO.s:17380: Error: thumb conditional instruction should be in IT block -- `strexeq r1,r2,[r6]'
>> ccVnNycO.s:19163: Error: thumb conditional instruction should be in IT block -- `strexeq r8,r6,[r3]'
>> ccVnNycO.s:22722: Error: thumb conditional instruction should be in IT block -- `strexeq r7,r1,[r0]'
>> ccVnNycO.s:24105: conditional infixes are deprecated in unified syntax
>> ccVnNycO.s:24105: Error: thumb conditional instruction should be in IT block -- `sbcccs r1,r1,r3'
>> ccVnNycO.s:24105: Error: thumb conditional instruction should be in IT block -- `movcc r3,#0'
>> ccVnNycO.s:24210: conditional infixes are deprecated in unified syntax
>> ccVnNycO.s:24210: Error: thumb conditional instruction should be in IT block -- `sbcccs r2,r2,r3'
>> ccVnNycO.s:24210: Error: thumb conditional instruction should be in IT block -- `movcc r3,#0'
>>
>> I did not investigate this too much, disabling Thumb2 support when LTO is
>> set lets me build randconfig kernels.
>>
>> Since ARM_SINGLE_ARMV7M is Thumb2-only, I have to disallow LTO for V7-M
>> targets.
>
> Here's the workaround I sent you on January 2rd:

Hmm, I thought I had applied that correctly but looking again now I
must have overwritten
the assembler when I reinstalled the toolchain from source to get a
fixed version of the
compiler.

       Arnd