According to System V i386 ABI: the __m64 type paramater and return
value are passed by MMX registers. But current implementation treats
__m64 as i64 which results in parameter passing by stack and returning
by EDX and EAX.
This patch fixes the bug (https://bugs.llvm.org/show_bug.cgi?id=41029)
for Linux and NetBSD.
Patch by Wei Xiao (wxiao3)
Differential Revision: https://reviews.llvm.org/D59744
llvm-svn: 363116
Pengfei Wang