LLVM now enforces the following prototypes for the write barriers:
<ty>* @llvm.gcread(<ty2>*, <ty>**)
void @llvm.gcwrite(<ty>*, <ty2>*, <ty>**)
And for @llvm.gcroot, the first stack slot is verified to be an alloca or a
bitcast of an alloca.
Fixes test/CodeGen/Generic/GC/lower_gcroot.ll, which violated these.
llvm-svn: 42051
