[IMCC] Updated register allocation used register stacks to persist across individual SymReg scans, which I accidentally left out of r28478.
[IMCC] Updated register allocation used register stacks to persist across
individual SymReg scans, which I accidentally left out of r28478.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@28479 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

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