[FIX] Do not create a SCoP in the presence of infinite loops

If a loop has no exiting blocks the region covering we use during
  schedule genertion might not cover that loop properly. For now we bail
  out as we would not optimize these loops anyway.

llvm-svn: 265280

polly/lib/Analysis/ScopDetection.cpp

@@ -1029,8 +1029,14 @@ bool ScopDetection::canUseISLTripCount(Loop *L,
   // Ensure the loop has valid exiting blocks as well as latches, otherwise we
   // need to overapproximate it as a boxed loop.
   SmallVector<BasicBlock *, 4> LoopControlBlocks;
-  L->getLoopLatches(LoopControlBlocks);
   L->getExitingBlocks(LoopControlBlocks);
+
+  // Loops without exiting blocks cannot be handled by the schedule generation
+  // as it depends on a region covering that is not given.
+  if (LoopControlBlocks.empty())
+    return false;
+
+  L->getLoopLatches(LoopControlBlocks);
   for (BasicBlock *ControlBB : LoopControlBlocks) {
     if (!isValidCFG(*ControlBB, true, false, Context))
       return false;

polly/lib/Analysis/ScopInfo.cpp

@@ -3680,7 +3680,7 @@ void Scop::buildSchedule(Region *R, LoopStackTy &LoopStack, ScopDetection &SD,
 
     Loop *LastLoop = LoopStack.back().L;
     if (LastLoop != L) {
-      if (!LastLoop->contains(L)) {
+      if (LastLoop && !LastLoop->contains(L)) {
         LastRNWaiting = true;
         DelayList.push_back(RN);
         continue;

polly/test/ScopInfo/schedule-constuction-endless-loop1.ll

@@ -0,0 +1,34 @@
+; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
+;
+; Check that we do not build a SCoP and do not crash.
+;
+; CHECK-NOT: Statements
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; Function Attrs: nounwind uwtable
+define void @int_upsample(i32* %A) {
+entry:
+  %0 = load i8, i8* undef, align 1
+  %conv7 = zext i8 %0 to i32
+  br label %while.body.preheader
+
+while.body.preheader:                             ; preds = %entry
+  br label %while.body
+
+while.body:                                       ; preds = %if.end, %while.body.preheader
+  %outrow.036 = phi i32 [ %add23, %if.end ], [ 0, %while.body.preheader ]
+  br i1 true, label %if.end, label %while.body16
+
+while.body16:                                     ; preds = %while.body16, %while.body
+  br label %while.body16
+
+if.end:                                           ; preds = %while.body
+  store i32 0, i32* %A
+  %add23 = add nuw nsw i32 %outrow.036, 1
+  %cmp = icmp slt i32 %add23, 0
+  br i1 %cmp, label %while.body, label %while.end24
+
+while.end24:                                      ; preds = %if.end
+  ret void
+}

polly/test/ScopInfo/schedule-constuction-endless-loop2.ll

@@ -0,0 +1,37 @@
+; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
+;
+; Check that we do not build a SCoP and do not crash.
+;
+; CHECK-NOT: Statements
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; Function Attrs: nounwind uwtable
+define void @int_upsample(i32* %A) {
+entry:
+  %0 = load i8, i8* undef, align 1
+  %conv7 = zext i8 %0 to i32
+  br label %while.body.preheader
+
+while.body.preheader:                             ; preds = %entry
+  br label %while.body
+
+while.body:                                       ; preds = %if.end, %while.body.preheader
+  %outrow.036 = phi i32 [ %add23, %if.end ], [ 0, %while.body.preheader ]
+  br i1 true, label %if.end, label %while.body16
+
+while.body16:                                     ; preds = %while.body16, %while.body
+  br label %while.body16.split
+
+while.body16.split:
+  br label %while.body16
+
+if.end:                                           ; preds = %while.body
+  store i32 0, i32* %A
+  %add23 = add nuw nsw i32 %outrow.036, 1
+  %cmp = icmp slt i32 %add23, 0
+  br i1 %cmp, label %while.body, label %while.end24
+
+while.end24:                                      ; preds = %if.end
+  ret void
+}

polly/test/ScopInfo/two-loops-one-infinite.ll

@@ -1,16 +1,8 @@
 ; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
 ;
-; Verify we detect and create the SCoP correctly
+; Verify we do not create a SCoP in the presence of infinite loops.
 ;
-; CHECK:      Statements {
-; CHECK-NEXT:   Stmt_while_body_us
-; CHECK-NEXT:     Domain :=
-; CHECK-NEXT:       [a13] -> { Stmt_while_body_us[] };
-; CHECK-NEXT:     Schedule :=
-; CHECK-NEXT:       [a13] -> { Stmt_while_body_us[] -> [] };
-; CHECK-NEXT:     MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
-; CHECK-NEXT:       [a13] -> { Stmt_while_body_us[] -> MemRef_uuu[] };
-; CHECK-NEXT: }
+; CHECK-NOT:      Statements
 ;
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n8:16:32-S64"