On Sun, 2020-04-05 at 08:45 +0100, Richard Sandiford wrote:
> lra_assign has an assert to make sure that no pseudo is allocated
> to a conflicting hard register. It used to be restricted to
> !flag_ipa_ra, but in g:a1e6ee38e708ef2bdef4 I'd enabled it for
> flag_ipa_ra too. It then tripped a few times while building
> libstdc++ for mips-mti-linux.
>
> Previous patches fixed one of the problems: registers clobbered
> by the taking of an exception were being treated as live at the
> beginning of the EH receiver, and this got propagated to predecessor
> blocks. But it turns out that there was a second problem: eh_return
> data registers were also being marked live in the same way.
>
> These registers are defined by the unwinder and so in reality they
> really are live on entry to the EH receiver. But definitions can
> only happen in blocks, not on edges, so for liveness purposes
> we use artificial definitions at the start of the EH receiver.
> process_bb_lives should therefore model the effect of a definition,
> not a plain use.
>
> Tested this time by building a full mips-mti-linux-gnu toolchain
> (including the prerequisite 26 glibc sysroots). Also boostrapped
> & regression tested on aarch64-linux-gnu and x86_64-linux-gnu.
> OK to install?
>
> Richard
>
>
> 2020-04-05 Richard Sandiford <richard.sandif...@arm.com>
>
> gcc/
> PR rtl-optimization/92989
> * lra-lives.c (process_bb_lives): Do not treat eh_return data
> registers as being live at the beginning of the EH receiver.
OK
jeff
>
