I've had failing llvm-gcc bootstraps on x86_64 for about a week now.
It falls over when trying to link makedepend with a stage1 compiler:
[x86_64-off-opt]: libcpp.a(charset.o): In function `init_iconv_desc':
[x86_64-off-opt]: (.text+0xef7): undefined reference to `alloca'
[And hundreds more of similar nature]
Supposedly gcc doesn't inline alloca if -ansi or -fno-builtin is specified,
but neither one of those conditions hold for any file built during