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

[Eric Christopher]

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>
>
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