[NFC] Add flag to disable error block assumptions

The declaration as an "error block" is currently aggressive and not very
smart. This patch allows to disable error blocks completely. This might
be useful to prevent SCoP expansion to a point where the assumed context
becomes infeasible, thus the SCoP has to be discarded.

llvm-svn: 287271

polly/lib/Support/ScopHelper.cpp

@@ -30,6 +30,11 @@ using namespace polly;
 
 #define DEBUG_TYPE "polly-scop-helper"
 
+static cl::opt<bool> PollyAllowErrorBlocks(
+    "polly-allow-error-blocks",
+    cl::desc("Allow to speculate on the execution of 'error blocks'."),
+    cl::Hidden, cl::init(true), cl::ZeroOrMore, cl::cat(PollyCategory));
+
 bool polly::hasInvokeEdge(const PHINode *PN) {
   for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i)
     if (InvokeInst *II = dyn_cast<InvokeInst>(PN->getIncomingValue(i)))
@@ -372,6 +377,8 @@ Value *polly::expandCodeFor(Scop &S, ScalarEvolution &SE, const DataLayout &DL,
 
 bool polly::isErrorBlock(BasicBlock &BB, const Region &R, LoopInfo &LI,
                          const DominatorTree &DT) {
+  if (!PollyAllowErrorBlocks)
+    return false;
 
   if (isa<UnreachableInst>(BB.getTerminator()))
     return true;