ip gets modified when FrameAndConstantPoolScope scope ends.
Using another register to store the start of the returned
instr.

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2765713003
Cr-Commit-Position: refs/heads/master@{#43999}