[LV] Add test cases with multiple exits which require versioning.

This adds some test coverage for
caafdf0, which relaxed an assertion
to only require a unique exit block.

Author: fhahn

llvm/test/Transforms/LoopVectorize/multiple-exits-versioning.ll

@@ -0,0 +1,67 @@
+; RUN: opt -loop-vectorize -force-vector-width=2 -S %s | FileCheck %s
+
+; Test cases to make sure LV & loop versioning can handle loops with
+; multiple exiting branches.
+
+; Multiple branches exiting the loop to a unique exit block. The loop should
+; be vectorized with versioning & noalias metadata should be added.
+define void @multiple_exits_unique_exit_block(i32* %A, i32* %B, i64 %N) {
+; CHECK-LABEL: @multiple_exits_unique_exit_block
+; CHECK:       vector.memcheck:
+; CHECK-LABEL: vector.body:
+; CHECK:         %wide.load = load <2 x i32>, <2 x i32>* {{.*}}, align 4, !alias.scope
+; CHECK:         store <2 x i32> %wide.load, <2 x i32>* {{.*}}, align 4, !alias.scope
+; CHECK:         br
+;
+entry:
+  br label %loop.header
+
+loop.header:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  %cond.0 = icmp eq i64 %iv, %N
+  br i1 %cond.0, label %exit, label %for.body
+
+for.body:
+  %A.gep = getelementptr inbounds i32, i32* %A, i64 %iv
+  %lv = load i32, i32* %A.gep, align 4
+  %B.gep = getelementptr inbounds i32, i32* %B, i64 %iv
+  store i32 %lv, i32* %B.gep, align 4
+  %iv.next = add nuw i64 %iv, 1
+  %cond.1 = icmp ult i64 %iv.next, 1000
+  br i1 %cond.1, label %loop.header, label %exit
+
+exit:
+  ret void
+}
+
+
+; Multiple branches exiting the loop to different blocks. Currently this is not supported.
+define i32 @multiple_exits_multiple_exit_blocks(i32* %A, i32* %B, i64 %N) {
+; CHECK-LABEL: @multiple_exits_multiple_exit_blocks
+; CHECK-NEXT:    entry:
+; CHECK:           br label %loop.header
+; CHECK-NOT:      <2 x i32>
+;
+entry:
+  br label %loop.header
+
+loop.header:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  %cond.0 = icmp eq i64 %iv, %N
+  br i1 %cond.0, label %exit.0, label %for.body
+
+for.body:
+  %A.gep = getelementptr inbounds i32, i32* %A, i64 %iv
+  %lv = load i32, i32* %A.gep, align 4
+  %B.gep = getelementptr inbounds i32, i32* %B, i64 %iv
+  store i32 %lv, i32* %B.gep, align 4
+  %iv.next = add nuw i64 %iv, 1
+  %cond.1 = icmp ult i64 %iv.next, 1000
+  br i1 %cond.1, label %loop.header, label %exit.1
+
+exit.0:
+  ret i32 1
+
+exit.1:
+  ret i32 2
+}