fix PR5009 by making CGSCCPM realize that a call was devirtualized
if an indirect call site was removed and a direct one was added, not
just if an indirect call site was modified to be direct.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102830 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/IPA/CallGraphSCCPass.cpp b/lib/Analysis/IPA/CallGraphSCCPass.cpp
index 288a7ef..0c01ee5 100644
--- a/lib/Analysis/IPA/CallGraphSCCPass.cpp
+++ b/lib/Analysis/IPA/CallGraphSCCPass.cpp
@@ -191,6 +191,10 @@
// Walk the function body looking for call sites. Sync up the call sites in
// CGN with those actually in the function.
+
+ // Keep track of the number of direct and indirect calls that were
+ // invalidated and removed.
+ unsigned NumDirectRemoved = 0, NumIndirectRemoved = 0;
// Get the set of call sites currently in the function.
for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) {
@@ -209,6 +213,12 @@
assert(!CheckingMode &&
"CallGraphSCCPass did not update the CallGraph correctly!");
+ // If this was an indirect call site, count it.
+ if (I->second->getFunction() == 0)
+ ++NumIndirectRemoved;
+ else
+ ++NumDirectRemoved;
+
// Just remove the edge from the set of callees, keep track of whether
// I points to the last element of the vector.
bool WasLast = I + 1 == E;
@@ -230,6 +240,9 @@
}
// Loop over all of the instructions in the function, getting the callsites.
+ // Keep track of the number of direct/indirect calls added.
+ unsigned NumDirectAdded = 0, NumIndirectAdded = 0;
+
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
CallSite CS = CallSite::get(I);
@@ -286,19 +299,34 @@
assert(!CheckingMode &&
"CallGraphSCCPass did not update the CallGraph correctly!");
- // If the call site didn't exist in the CGN yet, add it. We assume that
- // newly introduced call sites won't be indirect. This could be fixed
- // in the future.
+ // If the call site didn't exist in the CGN yet, add it.
CallGraphNode *CalleeNode;
- if (Function *Callee = CS.getCalledFunction())
+ if (Function *Callee = CS.getCalledFunction()) {
CalleeNode = CG.getOrInsertFunction(Callee);
- else
+ ++NumDirectAdded;
+ } else {
CalleeNode = CG.getCallsExternalNode();
+ ++NumIndirectAdded;
+ }
CGN->addCalledFunction(CS, CalleeNode);
MadeChange = true;
}
+ // We scanned the old callgraph node, removing invalidated call sites and
+ // then added back newly found call sites. One thing that can happen is
+ // that an old indirect call site was deleted and replaced with a new direct
+ // call. In this case, we have devirtualized a call, and CGSCCPM would like
+ // to iteratively optimize the new code. Unfortunately, we don't really
+ // have a great way to detect when this happens. As an approximation, we
+ // just look at whether the number of indirect calls is reduced and the
+ // number of direct calls is increased. There are tons of ways to fool this
+ // (e.g. DCE'ing an indirect call and duplicating an unrelated block with a
+ // direct call) but this is close enough.
+ if (NumIndirectRemoved > NumIndirectAdded &&
+ NumDirectRemoved < NumDirectAdded)
+ DevirtualizedCall = true;
+
// After scanning this function, if we still have entries in callsites, then
// they are dangling pointers. WeakVH should save us for this, so abort if
// this happens.
@@ -315,6 +343,9 @@
for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
I != E; ++I)
(*I)->dump();
+ if (DevirtualizedCall)
+ dbgs() << "CGSCCPASSMGR: Refresh devirtualized a call!\n";
+
} else {
dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
}