segfault while compiling stage2 libsyntax for i686-pc-windows-gnu

[Diggsey]

@alexcrichton has indicated this may be related to using newer versions of gcc, which might explain why it doesn't fail on the buildbot machines.

The segfault occurs while running the tailcallelim llvm pass on ast::Pat_::drop(), possibly during the prerequisite tti analysis.

Turning on any kind of debug information for either rust or llvm causes the problem to disappear.

[Diggsey]

I've reported this as an LLVM bug: https://llvm.org/bugs/show_bug.cgi?id=24722

[alexcrichton]

Closing as a duplicate of #28962

[alexcrichton]

Er actually this has a smaller number, gonna go in favor of this.

[alexcrichton]

Also so this shows up in github search:

gcc 5.2 fails to build LLVM successfully on MinGW as it segfaults at runtime