Right way to represent flag-setting arithmetic instructions in MD files

Eric Botcazou ebotcazou@adacore.com
Fri Mar 10 10:23:00 GMT 2017

> My understanding was that the order of the two in this pattern here doesn't
> matter because there is an implicit PARALLEL around them, but I found that
> the compare-elimination pass (compare-elim.c) assumes that the COMPARE set
> must be in the second position for it to do the transformations it wants.

Why do you want to use the compare-elimination pass exactly if the flags are 
exposed before reload, as is the case on Aarch64 I think?  The combiner is 
supposed to do the same job instead for these targets.

Eric Botcazou

More information about the Gcc mailing list