Summary:
Often, a code will call multiple virtual methods of a given object.
If they go in a linear block, it should be possible to check vtable
before the first call, then store vtable pointer and reuse it for
the second vcall without any additional checks.
This is expected to have a positive performance impact on a hot
path in Blink, see https://crbug.com/634139.
Reviewers: kcc
Differential Revision: https://reviews.llvm.org/D23151
llvm-svn: 277795
Filipe Cabecinhas