The define for 64 bit sign extension neglected to

initialize fields of the class that it used.

The result was nonsense code.

Before:
0000000000000000 <foo>:
   0:    00441100     0x441100
   4:    03e00008     jr    ra
   8:    00000000     nop

After:
0000000000000000 <foo>:
   0:    00041000     sll    v0,a0,0x0
   4:    03e00008     jr    ra
   8:    00000000     nop 

llvm-svn: 161377