[PATCH] ARM: Emit ".code 16" before global inline-asm instructions in thumb mode

[Eric Christopher]

On Thu, Jul 24, 2014 at 5:27 PM, Jim Grosbach <grosbach at apple.com> wrote:
> For the assembler, there’s no concept of that. It always starts in ARM mode. Even for the compiler, the defaulting to thumb mode for armv7 is a darwin only thing, I think. Used to be, anyway.
>
> From another point of view, it also keeps us more compatible with other tools like gas.
>

o.O

Does gcc emit a .code16 for file level inline assembly when compiling
with -mthumb?

-eric

> -Jim
>
>
>> On Jul 24, 2014, at 5:24 PM, Eric Christopher <echristo at gmail.com> wrote:
>>
>> Why not just start the assembler in the right mode for the target
>> we're assembling?
>>
>> -eric
>>
>> On Thu, Jul 24, 2014 at 5:19 PM, Jim Grosbach <grosbach at apple.com> wrote:
>>> Hi Akira,
>>>
>>> Patch LGTM. The testcase should also run with ARM (a second RUN line w/ a
>>> distinct check prefix) w/ check lines there to verify we don’t emit the
>>> “.code 16” then.
>>>
>>> -Jim
>>>
>>> On Jul 24, 2014, at 3:02 PM, Akira Hatanaka <ahatanak at gmail.com> wrote:
>>>
>>> ToT clang (correctly) errors-out when the target is armv7 (thumb2) and the
>>> program it's compiling has an ARM mode file-level inline assembly statement:
>>>
>>> $ cat test2.c
>>>
>>> __asm__ ("stmib sp, {r0-r14};");
>>>
>>> $ clang -arch armv7  -S -o - test2.c
>>> .section __TEXT,__text,regular,pure_instructions
>>> .ios_version_min 5, 0
>>> .section __TEXT,__textcoal_nt,coalesced,pure_instructions
>>> .section __TEXT,__const_coal,coalesced
>>> .section __TEXT,__picsymbolstub4,symbol_stubs,none,16
>>> .section __TEXT,__StaticInit,regular,pure_instructions
>>> .section __TEXT,__cstring,cstring_literals
>>> .syntax unified
>>>                                        @ Start of file scope inline
>>> assembly
>>> <inline asm>:1:1: error: instruction requires: arm-mode
>>> stmib sp, {r0-r14};
>>>
>>> However, when the .s file is generated with -no-integrated-as first, and
>>> then assembled later, clang completes assembling the .s file without any
>>> errors.
>>>
>>> $ clang -arch armv7  -S -o test2.s -no-integrated-as test2.c
>>> $ clang -arch armv7  test2.s -c
>>>
>>> The attached patch fixes this discrepancy in clang's behavior by emitting
>>> directive ".code 16" before global inline-asm instructions when the target
>>> is thumb. Without this directive, clang assembles the global inline-asm
>>> instruction in ARM mode, since the assembler always starts in ARM mode and
>>> stays in that mode until it sees directives that instruct it to switch to
>>> thumb.
>>>
>>> <rdar://problem/17757232>
>>>
>>> <code16.patch>_______________________________________________
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>