[GISel]: While constructing the GISelWorklist make sure we reserve at least the required size to the underlying dense map.

https://reviews.llvm.org/D57931

This should save some unnecessary growing of the DenseMap.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353498 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed