[CGSCC] Add -abort-on-max-devirt-iterations-reached option

Aborts if we hit the max devirtualization iteration.
Will be useful for testing that changes to devirtualization don't cause
devirtualization to repeat passes more times than necessary.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D89519

Author: aeubanks

llvm/include/llvm/Analysis/CGSCCPassManager.h

@@ -559,6 +559,10 @@ createCGSCCToFunctionPassAdaptor(FunctionPassT Pass) {
   return CGSCCToFunctionPassAdaptor<FunctionPassT>(std::move(Pass));
 }
 
+/// Checks -abort-on-max-devirt-iterations-reached to see if we should report an
+/// error.
+void maxDevirtIterationsReached();
+
 /// A helper that repeats an SCC pass each time an indirect call is refined to
 /// a direct call by that pass.
 ///
@@ -711,6 +715,7 @@ class DevirtSCCRepeatedPass
 
       // Otherwise, if we've already hit our max, we're done.
       if (Iteration >= MaxIterations) {
+        maxDevirtIterationsReached();
         LLVM_DEBUG(
             dbgs() << "Found another devirtualization after hitting the max "
                       "number of repetitions ("

llvm/lib/Analysis/CGSCCPassManager.cpp

@@ -21,9 +21,11 @@
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/PassManagerImpl.h"
 #include "llvm/Support/Casting.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/TimeProfiler.h"
+#include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
 #include <iterator>
@@ -36,6 +38,11 @@ using namespace llvm;
 // template typedefs.
 namespace llvm {
 
+static cl::opt<bool> AbortOnMaxDevirtIterationsReached(
+    "abort-on-max-devirt-iterations-reached",
+    cl::desc("Abort when the max iterations for devirtualization CGSCC repeat "
+             "pass is reached"));
+
 // Explicit instantiations for the core proxy templates.
 template class AllAnalysesOn<LazyCallGraph::SCC>;
 template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
@@ -362,6 +369,11 @@ static void updateNewSCCFunctionAnalyses(LazyCallGraph::SCC &C,
   }
 }
 
+void llvm::maxDevirtIterationsReached() {
+  if (AbortOnMaxDevirtIterationsReached)
+    report_fatal_error("Max devirtualization iterations reached");
+}
+
 /// Helper function to update both the \c CGSCCAnalysisManager \p AM and the \c
 /// CGSCCPassManager's \c CGSCCUpdateResult \p UR based on a range of newly
 /// added SCCs.

llvm/test/Other/cgscc-devirt-iteration.ll

@@ -8,6 +8,9 @@
 ; RUN: opt -aa-pipeline=basic-aa -passes='cgscc(devirt<1>(function-attrs,function(gvn,instcombine)))' -S < %s | FileCheck %s --check-prefix=CHECK --check-prefix=AFTER --check-prefix=AFTER1
 ; RUN: opt -aa-pipeline=basic-aa -passes='cgscc(devirt<2>(function-attrs,function(gvn,instcombine)))' -S < %s | FileCheck %s --check-prefix=CHECK --check-prefix=AFTER --check-prefix=AFTER2
 ;
+; RUN: not --crash opt -abort-on-max-devirt-iterations-reached -aa-pipeline=basic-aa -passes='cgscc(devirt<1>(function-attrs,function(gvn,instcombine)))' -S < %s
+; RUN: opt -abort-on-max-devirt-iterations-reached -aa-pipeline=basic-aa -passes='cgscc(devirt<2>(function-attrs,function(gvn,instcombine)))' -S < %s
+;
 ; We also verify that the real O2 pipeline catches these cases.
 ; RUN: opt -aa-pipeline=basic-aa -passes='default<O2>' -S < %s | FileCheck %s --check-prefix=CHECK --check-prefix=AFTER --check-prefix=AFTER2