xmm0 is not saved across runtime call on x64 because MacroAssembler::EnterExitFrameEpilogue preserves only allocatable XMM registers unlike on ia32 where it preserves all registers.

Cleanup handling of shifts: SHR can deoptimize only when its a shift by 0, all other shift never deoptimize.

Fix type inference for i-to-t change instruction. On X64 this ensures that write-barrier is generated correctly.

R=danno@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10868032

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12373 ce2b1a6d-e550-0410-aec6-3dcde31c8c00