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Author SHA1 Message Date
Duncan P. N. Exon Smith 706f37e8df Linker: Fix references to uniqued nodes after r243883
r243883 started moving 'distinct' nodes instead of duplicated them in
lib/Linker.  This had the side-effect of sometimes not cloning uniqued
nodes that reference them.  I missed a corner case:

    !named = !{!0}
     = !{!1}
     = distinct !{!0}

 is the entry point for "remapping", and a temporary clone (say,
!0-temp) is created and mapped in case we need to model a uniquing
cycle.

    Recursive descent into .   is distinct, so we leave it alone,
    but update its operand to !0-temp.

Pop back out to .  Its only operand, , hasn't changed, so we don't
need to use !0-temp.  !0-temp goes out of scope, and we're finished
remapping, but we're left with:

    !named = !{!0}
     = !{!1}
     = distinct !{null} ; uh oh...

Previously, if  and !0-temp ended up with identical operands, then
!0-temp couldn't have been referenced at all.  Now that distinct nodes
don't get duplicated, that assumption is invalid.  We need to
!0-temp->replaceAllUsesWith() before freeing !0-temp.

I found this while running an internal `-flto -g` bootstrap.  Strangely,
there was no case of this in the open source bootstrap I'd done before
commit...

llvm-svn: 243961
2015-08-04 06:42:31 +00:00