x86_64: Use RegClassBySize() for field accesses

This patch optimizes x86_64 field accesses to use kAnyReg whenever possible
via RegClassBySize().  Previously, using kCoreReg is too strict.

Change-Id: I55a48765b9bfe6b11c4b09f85c4eb08a6e269f98
Signed-off-by: Chao-ying Fu <chao-ying.fu@intel.com>
1 file changed