Revert patch. It regresses:

define double @test2(i64 %A) {
   %B = bitcast i64 %A to double
   ret double %B
}

$ llvm-as < t.ll | llc -march=x86-64

before:

         .align  4
         .globl  _test2
_test2:
         movd %rdi, %xmm0
         ret

after:

_test2:
         subq $8, %rsp
         movq %rdi, (%rsp)
         movsd (%rsp), %xmm0
         addq $8, %rsp
         ret

llvm-svn: 37617