[Bug middle-end/46164] Local variables in specified registers don't work correctly with inline asm operands

["Hale.Wang at arm dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46164

Hale Wang <Hale.Wang at arm dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |Hale.Wang at arm dot com

--- Comment #7 from Hale Wang <Hale.Wang at arm dot com> ---
(In reply to Tim Pambor from comment #4)
> Created attachment 33307 [details]
> testcase for gcc 4.9.1
> 
> I think this bug is still present in gcc 4.9.1 and 4.8.4.
> 
> I could reproduce the problem with the attached testcase using gcc 4.8.4
> with -O1 and -Og and 4.9.1 with -O1. -O0, -O2, -O3, -Os generated correct
> code. It generated the following assembler code:
> 
> ...
>   mov r0, r0	@ r0
>   mov r4, r4	@ r1
>   mov r2, r2	@ r2
> ...
> 
> Expected would have been:
> 
> ...
>   mov r0, r0	@ r0
>   mov r1, r1	@ r1
>   mov r2, r2	@ r2
> ...

The combine pass combined the volatile register which caused this bug.

The expected assembler code should be:

  mov r4, .L_temp
  mov r1, r4
  ...
  mov r0, r0    @ r0
  mov r1, r1    @ r1
  mov r2, r2    @ r2

But GCC combined the insns, and the code is generated as:

  mov r4, .L_temp
  ...
  mov r0, r0    @ r0
  mov r4, r4    @ r1
  mov r2, r2    @ r2

The register 'r1' is defined as volatile in this case. It should not be
combined.