Do not detect scops that are delinearized to arrays with "undef" size

Such codes are not interesting to optimize and most likely never appear in the
normal compilation flow. However, they show up during test case reduction with
bugpoint and trigger -- without this change -- an assert in
polly::MemoryAccess::foldAccess(). It is better to detect them in
ScopDetection itself and just bail out.

Contributed-by:  Utpal Bora  <cs14mtech11017@iith.ac.in>

Reviewers: grosser

Subscribers: pollydev, llvm-commits

Differential Revision: http://reviews.llvm.org/D11425

llvm-svn: 243515

polly/lib/Analysis/ScopDetection.cpp

@@ -512,11 +512,21 @@ bool ScopDetection::hasAffineMemoryAccesses(DetectionContext &Context) const {
                             Context.ElementSize[BasePointer]);
 
     if (!AllowNonAffine)
-      for (const SCEV *DelinearizedSize : Shape->DelinearizedSizes)
+      for (const SCEV *DelinearizedSize : Shape->DelinearizedSizes) {
+        if (auto *Unknown = dyn_cast<SCEVUnknown>(DelinearizedSize)) {
+          auto *value = dyn_cast<Value>(Unknown->getValue());
+          if (isa<UndefValue>(value)) {
+            invalid<ReportDifferentArrayElementSize>(
+                Context, /*Assert=*/true,
+                Context.Accesses[BasePointer].front().first, BaseValue);
+            return false;
+          }
+        }
         if (hasScalarDepsInsideRegion(DelinearizedSize, &CurRegion))
           invalid<ReportNonAffineAccess>(
               Context, /*Assert=*/true, DelinearizedSize,
               Context.Accesses[BasePointer].front().first, BaseValue);
+      }
 
     // No array shape derived.
     if (Shape->DelinearizedSizes.empty()) {

polly/test/ScopDetect/restrict-undef-size-scopdetect.ll

@@ -0,0 +1,33 @@
+; RUN: opt %loadPolly -polly-detect -analyze  < %s | FileCheck %s
+; CHECK-NOT: Valid Region for Scop:
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+%struct.bar = type { i32, [4 x i32] }
+
+define void @f(%struct.bar* %arg) {
+bb:
+  %tmp = alloca [4 x i32], align 16
+  br label %bb1
+
+bb1:                                              ; preds = %bb8, %bb
+  %tmp2 = phi i64 [ 0, %bb ], [ %tmp9, %bb8 ]
+  br i1 false, label %bb3, label %bb6
+
+bb3:                                              ; preds = %bb1
+  %tmp4 = getelementptr inbounds [4 x i32], [4 x i32]* %tmp, i64 0, i64 0
+  %tmp5 = load i32, i32* %tmp4
+  br label %bb8
+
+bb6:                                              ; preds = %bb1
+  %tmp7 = getelementptr inbounds %struct.bar, %struct.bar* %arg, i64 0, i32 1, i64 undef
+  store i32 42, i32* %tmp7
+  br label %bb8
+
+bb8:                                              ; preds = %bb6, %bb3
+  %tmp9 = add nuw nsw i64 %tmp2, 1
+  br i1 false, label %bb1, label %bb10
+
+bb10:                                             ; preds = %bb8
+  ret void
+}