Improve RefreshCallGraph to remove invalid call graph edge.
With commit r219944, InstCombine can now turn a sqrtl into a llvm.fabs.f64.
The call graph edge originally representing the call to sqrtl becomes invalid.
This patch modifies CGPassManager::RefreshCallGraph() to remove the invalid
call graph edge, which can triggers an assert in
CallGraphNode::addCalledFunction().
Phabricator Review: http://reviews.llvm.org/D7705
Patch by Lawrence Hu <lawrence@codeaurora.org>.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234902
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