3 files changed, 34 insertions, 21 deletions

diff --git a/polly/lib/Analysis/ScopDetection.cpp b/polly/lib/Analysis/ScopDetection.cpp
index fefdf67e51b..6371a2ec15b 100644
--- a/polly/lib/Analysis/ScopDetection.cpp
+++ b/polly/lib/Analysis/ScopDetection.cpp
@@ -973,7 +973,7 @@ bool ScopDetection::allBlocksValid(DetectionContext &Context) const {
 
   for (BasicBlock *BB : CurRegion.blocks()) {
     // Do not check exception blocks as we will never include them in the SCoP.
-    if (isErrorBlock(*BB))
+    if (isErrorBlock(*BB, CurRegion, *LI, *DT))
       continue;
 
     if (!isValidCFG(*BB, false, Context) && !KeepGoing)
@@ -1096,6 +1096,7 @@ bool ScopDetection::runOnFunction(llvm::Function &F) {
 
   AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
   SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
+  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
   Region *TopRegion = RI->getTopLevelRegion();
 
   releaseMemory();
@@ -1171,6 +1172,7 @@ void polly::ScopDetection::verifyAnalysis() const {
 void ScopDetection::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<LoopInfoWrapperPass>();
   AU.addRequired<ScalarEvolutionWrapperPass>();
+  AU.addRequired<DominatorTreeWrapperPass>();
   // We also need AA and RegionInfo when we are verifying analysis.
   AU.addRequiredTransitive<AAResultsWrapperPass>();
   AU.addRequiredTransitive<RegionInfoPass>();
@@ -1205,6 +1207,7 @@ INITIALIZE_PASS_BEGIN(ScopDetection, "polly-detect",
 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass);
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
 INITIALIZE_PASS_DEPENDENCY(RegionInfoPass);
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass);
 INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass);
 INITIALIZE_PASS_END(ScopDetection, "polly-detect",
                     "Polly - Detect static control parts (SCoPs)", false, false)
diff --git a/polly/lib/Analysis/ScopInfo.cpp b/polly/lib/Analysis/ScopInfo.cpp
index 05a5213a9f1..315ef714b3a 100644
--- a/polly/lib/Analysis/ScopInfo.cpp
+++ b/polly/lib/Analysis/ScopInfo.cpp
@@ -1698,11 +1698,12 @@ static inline unsigned getNumBlocksInRegionNode(RegionNode *RN) {
   return NumBlocks;
 }
 
-static bool containsErrorBlock(RegionNode *RN) {
+static bool containsErrorBlock(RegionNode *RN, const Region &R, LoopInfo &LI,
+                               const DominatorTree &DT) {
   if (!RN->isSubRegion())
-    return isErrorBlock(*RN->getNodeAs<BasicBlock>());
+    return isErrorBlock(*RN->getNodeAs<BasicBlock>(), R, LI, DT);
   for (BasicBlock *BB : RN->getNodeAs<Region>()->blocks())
-    if (isErrorBlock(*BB))
+    if (isErrorBlock(*BB, R, LI, DT))
       return true;
   return false;
 }
@@ -1785,7 +1786,7 @@ void Scop::buildDomainsWithBranchConstraints(Region *R) {
     // the predecessors and can therefor look at the domain of a error block.
     // That allows us to generate the assumptions needed for them not to be
     // executed at runtime.
-    if (containsErrorBlock(RN))
+    if (containsErrorBlock(RN, getRegion(), LI, DT))
       continue;
 
     BasicBlock *BB = getRegionNodeBasicBlock(RN);
@@ -1993,7 +1994,7 @@ void Scop::propagateDomainConstraints(Region *R) {
       addLoopBoundsToHeaderDomain(BBLoop);
 
     // Add assumptions for error blocks.
-    if (containsErrorBlock(RN)) {
+    if (containsErrorBlock(RN, getRegion(), LI, DT)) {
       IsOptimized = true;
       isl_set *DomPar = isl_set_params(isl_set_copy(Domain));
       addAssumption(isl_set_complement(DomPar));
@@ -2888,7 +2889,7 @@ bool Scop::isIgnored(RegionNode *RN) {
     return true;
 
   // Check if error blocks are contained.
-  if (containsErrorBlock(RN))
+  if (containsErrorBlock(RN, getRegion(), LI, DT))
     return true;
 
   return false;
diff --git a/polly/lib/Support/ScopHelper.cpp b/polly/lib/Support/ScopHelper.cpp
index d2123bd69eb..022f427ecc8 100644
--- a/polly/lib/Support/ScopHelper.cpp
+++ b/polly/lib/Support/ScopHelper.cpp
@@ -28,11 +28,6 @@ using namespace polly;
 
 #define DEBUG_TYPE "polly-scop-helper"
 
-static cl::list<std::string>
-    ErrorFunctions("polly-error-functions",
-                   cl::desc("A list of error functions"), cl::Hidden,
-                   cl::ZeroOrMore, cl::CommaSeparated, cl::cat(PollyCategory));
-
 Value *polly::getPointerOperand(Instruction &Inst) {
   if (LoadInst *load = dyn_cast<LoadInst>(&Inst))
     return load->getPointerOperand();
@@ -346,22 +341,36 @@ Value *polly::expandCodeFor(Scop &S, ScalarEvolution &SE, const DataLayout &DL,
   return Expander.expandCodeFor(E, Ty, IP);
 }
 
-bool polly::isErrorBlock(BasicBlock &BB) {
+bool polly::isErrorBlock(BasicBlock &BB, const Region &R, LoopInfo &LI,
+                         const DominatorTree &DT) {
 
   if (isa<UnreachableInst>(BB.getTerminator()))
     return true;
 
-  if (ErrorFunctions.empty())
+  if (LI.isLoopHeader(&BB))
+    return false;
+
+  if (DT.dominates(&BB, R.getExit()))
+    return false;
+
+  // FIXME: This is a simple heuristic to determine if the load is executed
+  //        in a conditional. However, we actually would need the control
+  //        condition, i.e., the post dominance frontier. Alternatively we
+  //        could walk up the dominance tree until we find a block that is
+  //        not post dominated by the load and check if it is a conditional
+  //        or a loop header.
+  auto *DTNode = DT.getNode(&BB);
+  auto *IDomBB = DTNode->getIDom()->getBlock();
+  if (LI.isLoopHeader(IDomBB))
     return false;
 
   for (Instruction &Inst : BB)
-    if (CallInst *CI = dyn_cast<CallInst>(&Inst))
-      if (Function *F = CI->getCalledFunction()) {
-        const auto &FnName = F->getName();
-        for (const auto &ErrorFn : ErrorFunctions)
-          if (FnName.equals(ErrorFn))
-            return true;
-      }
+    if (CallInst *CI = dyn_cast<CallInst>(&Inst)) {
+      if (!CI->doesNotAccessMemory())
+        return true;
+      if (CI->doesNotReturn())
+        return true;
+    }
 
   return false;
 }