PR bootstrap/48327

Jeff Law law@redhat.com
Wed Mar 30 01:38:00 GMT 2011


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The underlying problem here is a botched update of a PHI argument when
we thread all incoming edges for a particular block.

In that case we used to use the original block as the template block
which saved a little bit of memory at the expense of slightly more
complex SSA updating.

However, after looking a some of the changes over the last few years to
tree-ssa-threadupdate.c, I'm not sure that's safe anymore.  Furthermore,
the SSA graph updating code was going to need another hack to deal with
the case where we thread deeper into the CFG.

Rather than try to make those two things work, it's easier to just
delete all the code which tried to reuse the soon-to-be-unreachable
block.  I like it when removing code fixes bugs.

Installed after a bootstrap and regression test cycle (including Ada
bootstrapping which triggered the bug report).


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