[PATCH] D69411: [MC] Calculate difference of symbols in two fragments when possible

[Jian Cai via Phabricator via llvm-commits]

jcai19 added a comment.

In D69411#1725261 <https://reviews.llvm.org/D69411#1725261>, @peter.smith wrote:

> I'd like to see some more test cases for the error cases. Off the top of my head I can think of these cases:
>
>   // Align fragment in between MCDataFragments
>   9997: nop ;
>         .align 4
>         nop
>   .if . - 9997b == 4 ;
>
>
>   // Fill (I think) fragment in between MCDataFragments
>   9997: nop ;
>         .space 4
>         nop
>   .if . - 9997b == 4 ;
>
>
>   // Relaxable (in Thumb) fragment in between MCDataFragments
>   9997: nop ;
>         b external
>         nop
>   .if . - 9997b == 4 ;
>
>
>   // Constant pool between MCDataFragments,
>   9997:
>         ldr r0,=0x12345678 ;
>         .ltorg
>         nop  
>   .if . - 9997b == 4 ;
>
>
> There is also something called a MCCompactEncodingInstFragment that would cause this to fail, but I think that only exists as part of NaCl bundle locking, which I think isn't too much of a concern.


Thanks for providing these test cases! It seems the third and fourth case do not produce any errors as expected (even with arm gcc). Will dig more.


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