[Bug target/66655] [5/6 Regression] miscompilation due to ipa-ra on MinGW

[rogero at howzatt dot demon.co.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66655

--- Comment #24 from Roger Orr <rogero at howzatt dot demon.co.uk> ---
Thanks Nick.

I've tried the patch (applied to 232400 as trunk seems to have other problems
on cygwin) and the build now completes successfully.

Additionally, the test case no longer crashes.

$ /usr/share/gcc-trunk/bin/g++ -O2 -fno-inline pr66655.C pr66655_1.cc
$ ./a.exe
$ /usr/share/gcc-trunk/bin/g++ -O2 -fno-inline pr66655_1.cc pr66655.C
$ ./a.exe

$ /usr/share/gcc-trunk/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/usr/share/gcc-trunk/bin/g++
COLLECT_LTO_WRAPPER=/usr/share/gcc-trunk/libexec/gcc/x86_64-unknown-cygwin/6.0.0/lto-wrapper.exe
Target: x86_64-unknown-cygwin
Configured with: ../gcc-trunk-232400/configure --enable-languages=c,c++
--prefix=/usr/share/gcc-trunk
Thread model: single
gcc version 6.0.0 20160115 (experimental) (GCC)