Don't expand to invalid Scops with -polly-detect-keep-going

Enabling -keep-going in ScopDetection causes expansion to an invalid
Scop candidate.

Region A     <- Valid candidate
   |
Region B     <- Invalid candidate

If -keep-going is enabled, ScopDetection would expand A to A+B because
the RejectLog is never checked for errors during expansion.

With this patch only A becomes a valid Scop.

llvm-svn: 211875

polly/include/polly/ScopDetectionDiagnostic.h

@@ -174,6 +174,7 @@ public:
   iterator begin() const { return ErrorReports.begin(); }
   iterator end() const { return ErrorReports.end(); }
   size_t size() const { return ErrorReports.size(); }
+  bool hasErrors() const { return size() > 0; }
 
   const Region *region() const { return R; }
   void report(RejectReasonPtr Reject) { ErrorReports.push_back(Reject); }

polly/lib/Analysis/ScopDetection.cpp

@@ -546,13 +546,17 @@ Region *ScopDetection::expandRegion(Region &R) {
   while (ExpandedRegion) {
     DetectionContext Context(*ExpandedRegion, *AA, false /* verifying */);
     DEBUG(dbgs() << "\t\tTrying " << ExpandedRegion->getNameStr() << "\n");
+    // Only expand when we did not collect errors.
 
     // Check the exit first (cheap)
-    if (isValidExit(Context)) {
+    if (isValidExit(Context) && !Context.Log.hasErrors()) {
       // If the exit is valid check all blocks
       //  - if true, a valid region was found => store it + keep expanding
       //  - if false, .tbd. => stop  (should this really end the loop?)
-      if (!allBlocksValid(Context))
+      if (!allBlocksValid(Context) || Context.Log.hasErrors())
+        break;
+
+      if (Context.Log.hasErrors())
         break;
 
       // Delete unnecessary regions (allocated by getExpandedRegion)
@@ -628,10 +632,6 @@ void ScopDetection::findScops(Region &R) {
   for (auto &SubRegion : R)
     findScops(*SubRegion);
 
-  // Do not expand when we had errors. Bad things may happen.
-  if (IsValidRegion && HasErrors)
-    return;
-
   // Try to expand regions.
   //
   // As the region tree normally only contains canonical regions, non canonical
@@ -644,6 +644,11 @@ void ScopDetection::findScops(Region &R) {
     ToExpand.push_back(SubRegion.get());
 
   for (Region *CurrentRegion : ToExpand) {
+    // Skip regions that had errors.
+    bool HadErrors = RejectLogs.hasErrors(CurrentRegion);
+    if (HadErrors)
+      continue;
+
     // Skip invalid regions. Regions may become invalid, if they are element of
     // an already expanded region.
     if (ValidRegions.find(CurrentRegion) == ValidRegions.end())

polly/test/ScopDetect/keep_going_expansion.ll

@@ -0,0 +1,46 @@
+; RUN: opt %loadPolly -basicaa -polly-detect-track-failures -polly-detect-keep-going -polly-detect -analyze < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @a(i32 %n, i32* noalias %A, i32* noalias %B) #0 {
+entry:
+  br label %entry.split
+
+entry.split:                                      ; preds = %entry
+  br label %for.body
+
+for.cond2.preheader:                              ; preds = %for.body
+  br label %for.body4
+
+for.body:                                         ; preds = %entry.split, %for.body
+  %indvar = phi i64 [ 0, %entry.split ], [ %indvar.next, %for.body ]
+  %j.02 = trunc i64 %indvar to i32
+  %arrayidx = getelementptr i32* %B, i64 %indvar
+  store i32 %j.02, i32* %arrayidx, align 4
+  %indvar.next = add i64 %indvar, 1
+  %exitcond3 = icmp ne i64 %indvar.next, 32
+  br i1 %exitcond3, label %for.body, label %for.cond2.preheader
+
+for.body4:                                        ; preds = %for.cond2.preheader, %for.body4
+  %0 = phi i32 [ 0, %for.cond2.preheader ], [ %1, %for.body4 ]
+  %mul = mul i32 %n, %0
+  %idxprom5 = sext i32 %mul to i64
+  %arrayidx6 = getelementptr inbounds i32* %A, i64 %idxprom5
+  store i32 %0, i32* %arrayidx6, align 4
+  %1 = add nsw i32 %0, 1
+  %exitcond = icmp ne i32 %1, 32
+  br i1 %exitcond, label %for.body4, label %for.end9
+
+for.end9:                                         ; preds = %for.body4
+  %idxprom10 = sext i32 %n to i64
+  %arrayidx11 = getelementptr inbounds i32* %A, i64 %idxprom10
+  %2 = load i32* %arrayidx11, align 4
+  %idxprom12 = sext i32 %n to i64
+  %arrayidx13 = getelementptr inbounds i32* %B, i64 %idxprom12
+  %3 = load i32* %arrayidx13, align 4
+  %add = add nsw i32 %3, %2
+  ret i32 %add
+}
+
+; CHECK: Valid Region for Scop: for.body => for.cond2.preheader