[Polly] Never consider non-SCoP blocks as error blocks.

Code outside the SCoP will be executed recardless of the code versioning
runtime check introduced by CodeGeneration. Assumption made based on
that these are never executed in Polly-optimized code does not hold.

This fixes the miscompilation of MultiSource/Applications/lambda-0.1.3

Author: Meinersbur

polly/lib/Analysis/ScopBuilder.cpp

@@ -449,6 +449,9 @@ bool ScopBuilder::buildConditionSets(
   } else if (auto *PHI = dyn_cast<PHINode>(Condition)) {
     auto *Unique = dyn_cast<ConstantInt>(
         getUniqueNonErrorValue(PHI, &scop->getRegion(), &SD));
+    assert(Unique &&
+           "A PHINode condition should only be accepted by ScopDetection if "
+           "getUniqueNonErrorValue returns non-NULL");
 
     if (Unique->isZero())
       ConsequenceCondSet = isl_set_empty(isl_set_get_space(Domain));

polly/lib/Analysis/ScopDetection.cpp

@@ -1417,6 +1417,11 @@ static bool isErrorBlockImpl(BasicBlock &BB, const Region &R, LoopInfo &LI,
   if (LI.isLoopHeader(&BB))
     return false;
 
+  // Don't consider something outside the SCoP as error block. It will precede
+  // the code versioning runtime check.
+  if (!R.contains(&BB))
+    return false;
+
   // Basic blocks that are always executed are not considered error blocks,
   // as their execution can not be a rare event.
   bool DominatesAllPredecessors = true;

polly/test/ScopInfo/condition-after-error-block-before-scop.ll

@@ -0,0 +1,48 @@
+; RUN: opt %loadPolly -polly-scops -polly-codegen -S < %s | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%class.node = type { i32 (...)**, %class.node* }
+
+define void @foobar(double* %A) {
+if.end:
+  br i1 undef, label %if.then29, label %lor.lhs.false
+
+lor.lhs.false:
+  %call25 = tail call i32 undef(%class.node* undef)
+  br i1 undef, label %if.then29, label %if.end30
+
+if.then29:
+  br label %if.end30
+
+if.end30:
+  %tobool76.not = phi i1 [ false, %lor.lhs.false ], [ true, %if.then29 ]
+  br label %if.end75
+
+if.end75:
+  br label %if.end79
+
+if.end79:
+  br label %if.then84
+
+if.then84:
+  br label %if.end91
+
+if.end91:
+  br i1 %tobool76.not, label %if.end98, label %if.then93
+
+if.then93:
+  store double 0.0, double* %A
+  br label %if.end98
+
+if.end98:
+  %tobool131 = phi i1 [ false, %if.end91 ], [ true, %if.then93 ]
+  ret void
+}
+
+
+; CHECK: polly.stmt.if.then93:
+; CHECK:   store double 0.000000e+00, double* %A
+; CHECK:   br label %polly.exiting
+