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

[Jim Grosbach]

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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