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Re: i386 PATCH for target/13685


On Fri, Sep 08, 2006 at 08:14:37PM -0700, Mark Mitchell wrote:
> Jason Merrill wrote:
> >H. J. Lu wrote:
> >>On Thu, Sep 07, 2006 at 08:26:45PM -0400, Jason Merrill wrote:
> >>>The testcase in 13685 breaks because -Os implies a smaller 
> >>>PREFERRED_STACK_BOUNDARY than SSE requires.  This patch causes us to 
> >>>use the 128-bit boundary if SSE is enabled, which fixes the bug.
> >
> >>I think it is a bad idea for -Os to change ABI. There are several bugs
> >>open because of it. You can have a program compiled with -Os calling
> >>a library compiled with -msee. The program will crash since -Os
> >>uses a different ABI. The easiest way to fix is for -Os not to change
> >>the ABI automatically.
> >
> >I wouldn't mind changing the stack boundary to always be 128 bits.
> 
> FWIW, I would strongly suggest that we use a fixed ABI independent of 
> -Os, i.e., change the stack boundary to always be 128 bits.  I believe 
> that it should always be the case that code compiled with different -O 
> options can be freely intermixed (whereas -f/-m options may change the ABI).

This patch

http://gcc.gnu.org/ml/gcc-patches/2006-09/msg00298.html

does that.


H.J.


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