[Unroll] Handle SwitchInst properly.

Previously successor selection was simply wrong.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243545 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/LoopUnrollPass.cpp

@@ -619,8 +619,8 @@ analyzeLoopUnrollCost(const Loop *L, unsigned TripCount, ScalarEvolution &SE,
           if (isa<UndefValue>(SimpleCond))
             Succ = SI->getSuccessor(0);
           else
-            Succ =
-                SI->getSuccessor(cast<ConstantInt>(SimpleCond)->getSExtValue());
+            Succ = SI->findCaseValue(cast<ConstantInt>(SimpleCond))
+                       .getCaseSuccessor();
           if (L->contains(Succ))
             BBWorklist.insert(Succ);
           continue;

test/Transforms/LoopUnroll/full-unroll-crashers.ll

@@ -57,3 +57,27 @@ for.inc:                                          ; preds = %for.body, %if.then
 for.end:                                          ; preds = %for.inc
   ret void
 }
+
+define void @switch() {
+entry:
+  br label %for.body
+
+for.body:
+  %iv.0 = phi i64 [ 0, %entry ], [ %iv.1, %for.inc ]
+  %arrayidx1 = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv.0
+  %x1 = load i32, i32* %arrayidx1, align 4
+  switch i32 %x1, label %l1 [
+  ]
+
+l1:
+  %x2 = add i32 %x1, 2
+  br label %for.inc
+
+for.inc:
+  %iv.1 = add nuw nsw i64 %iv.0, 1
+  %exitcond = icmp eq i64 %iv.1, 10
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}