[X86] Use SmallVector::assign instead of resize to ensure we really start with a vector of all -1s. Otherwise we're trusting the caller to pass the right thing.
[X86] Use SmallVector::assign instead of resize to ensure we really start with a vector of all -1s. Otherwise we're trusting the caller to pass the right thing.

This should be no functional change with current code.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@273113 91177308-0d34-0410-b5e6-96231b3b80d8

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