#include "llvm/PassManagers.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/ADT/SCCIterator.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
+static cl::opt<unsigned>
+MaxIterations("max-cg-scc-iterations", cl::ReallyHidden, cl::init(0));
+
+STATISTIC(MaxSCCIterations, "Maximum CGSCCPassMgr iterations on one SCC");
+
//===----------------------------------------------------------------------===//
// CGPassManager
//
}
private:
+ bool RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
+ bool &DevirtualizedCall);
+
bool RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
- CallGraph &CG, bool &CallGraphUpToDate);
- void RefreshCallGraph(CallGraphSCC &CurSCC, CallGraph &CG,
+ CallGraph &CG, bool &CallGraphUpToDate,
+ bool &DevirtualizedCall);
+ bool RefreshCallGraph(CallGraphSCC &CurSCC, CallGraph &CG,
bool IsCheckingMode);
};
bool CGPassManager::RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
- CallGraph &CG, bool &CallGraphUpToDate) {
+ CallGraph &CG, bool &CallGraphUpToDate,
+ bool &DevirtualizedCall) {
bool Changed = false;
PMDataManager *PM = P->getAsPMDataManager();
if (PM == 0) {
CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
if (!CallGraphUpToDate) {
- RefreshCallGraph(CurSCC, CG, false);
+ DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
CallGraphUpToDate = true;
}
/// FunctionPasses have potentially munged the callgraph, and can be used after
/// CallGraphSCC passes to verify that they correctly updated the callgraph.
///
-void CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
+/// This function returns true if it devirtualized an existing function call,
+/// meaning it turned an indirect call into a direct call. This happens when
+/// a function pass like GVN optimizes away stuff feeding the indirect call.
+/// This never happens in checking mode.
+///
+bool CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
CallGraph &CG, bool CheckingMode) {
DenseMap<Value*, CallGraphNode*> CallSites;
);
bool MadeChange = false;
+ bool DevirtualizedCall = false;
// Scan all functions in the SCC.
unsigned FunctionNo = 0;
// If not, we either went from a direct call to indirect, indirect to
// direct, or direct to different direct.
CallGraphNode *CalleeNode;
- if (Function *Callee = CS.getCalledFunction())
+ if (Function *Callee = CS.getCalledFunction()) {
CalleeNode = CG.getOrInsertFunction(Callee);
- else
+ // Keep track of whether we turned an indirect call into a direct
+ // one.
+ if (ExistingNode->getFunction() == 0) {
+ DevirtualizedCall = true;
+ DEBUG(dbgs() << " CGSCCPASSMGR: Devirtualized call to '"
+ << Callee->getName() << "'\n");
+ }
+ } else {
CalleeNode = CG.getCallsExternalNode();
+ }
// Update the edge target in CGN.
for (CallGraphNode::iterator I = CGN->begin(); ; ++I) {
dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
}
);
+
+ return DevirtualizedCall;
+}
+
+/// RunAllPassesOnSCC - Execute the body of the entire pass manager on the
+/// specified SCC. This keeps track of whether a function pass devirtualizes
+/// any calls and returns it in DevirtualizedCall.
+bool CGPassManager::RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
+ bool &DevirtualizedCall) {
+ bool Changed = false;
+
+ // CallGraphUpToDate - Keep track of whether the callgraph is known to be
+ // up-to-date or not. The CGSSC pass manager runs two types of passes:
+ // CallGraphSCC Passes and other random function passes. Because other
+ // random function passes are not CallGraph aware, they may clobber the
+ // call graph by introducing new calls or deleting other ones. This flag
+ // is set to false when we run a function pass so that we know to clean up
+ // the callgraph when we need to run a CGSCCPass again.
+ bool CallGraphUpToDate = true;
+
+ // Run all passes on current SCC.
+ for (unsigned PassNo = 0, e = getNumContainedPasses();
+ PassNo != e; ++PassNo) {
+ Pass *P = getContainedPass(PassNo);
+
+ // If we're in -debug-pass=Executions mode, construct the SCC node list,
+ // otherwise avoid constructing this string as it is expensive.
+ if (isPassDebuggingExecutionsOrMore()) {
+ std::string Functions;
+ #ifndef NDEBUG
+ raw_string_ostream OS(Functions);
+ for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
+ I != E; ++I) {
+ if (I != CurSCC.begin()) OS << ", ";
+ (*I)->print(OS);
+ }
+ OS.flush();
+ #endif
+ dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
+ }
+ dumpRequiredSet(P);
+
+ initializeAnalysisImpl(P);
+
+ // Actually run this pass on the current SCC.
+ Changed |= RunPassOnSCC(P, CurSCC, CG,
+ CallGraphUpToDate, DevirtualizedCall);
+
+ if (Changed)
+ dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
+ dumpPreservedSet(P);
+
+ verifyPreservedAnalysis(P);
+ removeNotPreservedAnalysis(P);
+ recordAvailableAnalysis(P);
+ removeDeadPasses(P, "", ON_CG_MSG);
+ }
+
+ // If the callgraph was left out of date (because the last pass run was a
+ // functionpass), refresh it before we move on to the next SCC.
+ if (!CallGraphUpToDate)
+ DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
+ return Changed;
}
/// run - Execute all of the passes scheduled for execution. Keep track of
bool CGPassManager::runOnModule(Module &M) {
CallGraph &CG = getAnalysis<CallGraph>();
bool Changed = doInitialization(CG);
-
+
// Walk the callgraph in bottom-up SCC order.
scc_iterator<CallGraph*> CGI = scc_begin(&CG);
CurSCC.initialize(&NodeVec[0], &NodeVec[0]+NodeVec.size());
++CGI;
- // CallGraphUpToDate - Keep track of whether the callgraph is known to be
- // up-to-date or not. The CGSSC pass manager runs two types of passes:
- // CallGraphSCC Passes and other random function passes. Because other
- // random function passes are not CallGraph aware, they may clobber the
- // call graph by introducing new calls or deleting other ones. This flag
- // is set to false when we run a function pass so that we know to clean up
- // the callgraph when we need to run a CGSCCPass again.
- bool CallGraphUpToDate = true;
+ // At the top level, we run all the passes in this pass manager on the
+ // functions in this SCC. However, we support iterative compilation in the
+ // case where a function pass devirtualizes a call to a function. For
+ // example, it is very common for a function pass (often GVN or instcombine)
+ // to eliminate the addressing that feeds into a call. With that improved
+ // information, we would like the call to be an inline candidate, infer
+ // mod-ref information etc.
+ //
+ // Because of this, we allow iteration up to a specified iteration count.
+ // This only happens in the case of a devirtualized call, so we only burn
+ // compile time in the case that we're making progress. We also have a hard
+ // iteration count limit in case there is crazy code.
+ unsigned Iteration = 0;
+ bool DevirtualizedCall = false;
+ do {
+ DevirtualizedCall = false;
+ Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
+ } while (Iteration++ < MaxIterations && DevirtualizedCall);
- // Run all passes on current SCC.
- for (unsigned PassNo = 0, e = getNumContainedPasses();
- PassNo != e; ++PassNo) {
- Pass *P = getContainedPass(PassNo);
-
- // If we're in -debug-pass=Executions mode, construct the SCC node list,
- // otherwise avoid constructing this string as it is expensive.
- if (isPassDebuggingExecutionsOrMore()) {
- std::string Functions;
-#ifndef NDEBUG
- raw_string_ostream OS(Functions);
- for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
- I != E; ++I) {
- if (I != CurSCC.begin()) OS << ", ";
- (*I)->print(OS);
- }
- OS.flush();
-#endif
- dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
- }
- dumpRequiredSet(P);
-
- initializeAnalysisImpl(P);
-
- // Actually run this pass on the current SCC.
- Changed |= RunPassOnSCC(P, CurSCC, CG, CallGraphUpToDate);
-
- if (Changed)
- dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
- dumpPreservedSet(P);
-
- verifyPreservedAnalysis(P);
- removeNotPreservedAnalysis(P);
- recordAvailableAnalysis(P);
- removeDeadPasses(P, "", ON_CG_MSG);
- }
+ if (DevirtualizedCall)
+ DEBUG(dbgs() << " CGSCCPASSMGR: Stopped iteration after " << Iteration
+ << " times, due to -max-cg-scc-iterations\n");
+
+ if (Iteration > MaxSCCIterations)
+ MaxSCCIterations = Iteration;
- // If the callgraph was left out of date (because the last pass run was a
- // functionpass), refresh it before we move on to the next SCC.
- if (!CallGraphUpToDate)
- RefreshCallGraph(CurSCC, CG, false);
}
Changed |= doFinalization(CG);
return Changed;
}
+
/// Initialize CG
bool CGPassManager::doInitialization(CallGraph &CG) {
bool Changed = false;
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