Re: RFC -- targets with unsigned bifields

[Richard Biener <richard.guenther@gmail.com>]

> Am 17.12.2023 um 04:29 schrieb Jeff Law <jlaw@ventanamicro.com>:
> 
> 
> So mcore-elf is the slowest target to test with a simulator.  Not because it's simulator is particularly bad, but because some tests timeout as they've gotten into infinite loops.  This causes the mcore-elf port to take about 2X longer than most other gdbsim ports.
> 
> I tracked this down to the port unconditionally adding -funsigned-bitfields to CC1_SPEC.  According to the comment it's how the ABI is defined for the mcore targets.
> 
> It'd be nice to get reasonable results from mcore-elf in a reasonable amount of time.  The question is how.
> 
> I *could* just disable the -funsigned-bitfields within the tester.  We certainly have the ability to carry forward patches like this which exist only to help the testing effort.
> 
> Another approach would be to add an explicit -fsigned-bifields to the arguments for the affected tests.  I'd guess it's on the order of around 35 distinct tests that would need to be updated.
> 
> A third approach would be to grub around and see if there's a way to add a -fsigned-bitfields using dejagnu, perhaps in the baseboards file.

When the testcases are simply invalid with unsigned bitfields then I suggest to add a dg effective target we could require?  Or are the testcases actually miscompiled?

I suppose neither -f[un]signed-bitfields is the standard behavior but bitfield signedness is determined by the underlying type?  Or is this flag about sth else?

I could imagine a test needing the default behavior?

Richard 

> Looking for suggestions/recommendations here.
> 
> Jeff