Re: [Bug c++/44328] switch/case optimization produces an invalid lookup table index

[Andrew Pinski <pinskia at gmail dot com>]

I bet it could be reproduced on any target with -fshort-enums.

On Jun 17, 2010, at 2:20 AM, "eblot dot ml at gmail dot com" <gcc-bugzilla@gcc.gnu.org 
> wrote:

> ------- Comment #6 from eblot dot ml at gmail dot com  2010-06-17  
> 09:20 -------
> (In reply to comment #5)
> > Unfortunately I don't see this happening on the x86_64-linux ->
> > arm-linux-gnueabi cross compiler I built for myself.  The generated
> > assembly has all four elements in the initialization of CSWTCH.2 and
> > the intermediate tree dumps from the cross compiler are not really
> > different from the ones from a native x86_64 compiler.
>
> I think this might be due to the ABI differences between the  
> official ARM ABI
> (AAPCS) and the Linux variant, which is slightly different.
>
> I'd bet the way the enumerations are handled (variable size with  
> AAPCS, fixed,
> integer-native size with ARM Linux) is the 'culprit' here.
>
> See http://www.codesourcery.com/sgpp/lite/arm/arm_gnu_linux_abi.pdf
>
> The enumeration used in this bug report is coded as a byte with  
> AAPCS, whereas
> it should be coded as a 32-bit value with Linux ARM ABI. This might  
> explain why
> you cannot reproduce the issue with a Linux-target cross-compiler.
>
>
> --
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44328