When mixing SSE and x87 codegen, it's possible to

have situations where an SSE instruction turns into
multiple blocks, with the live range of an x87
register crossing them.  To do this correctly make
sure we examine all blocks when inserting
FP_REG_KILL.  PR 1697.  (This was exposed by my
fix for PR 1681, but the same thing could happen
mixing x87 long double with SSE.)

llvm-svn: 42281