[LV] Remove wrong assumption about LCSSA

The LCSSA pass itself will not generate several redundant PHI nodes in a single
exit block. However, such redundant PHI nodes don't violate LCSSA form, and may
be introduced by passes that preserve LCSSA, and/or preserved by the LCSSA pass
itself. So, assuming a single PHI node per exit block is not safe.

llvm-svn: 275217

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll b/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll
index 4e345f3517b..d536d1023f4 100644
--- a/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll
+++ b/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll
@@ -108,3 +108,28 @@ for.body:
 for.end:
   ret i32* %inc.lag1
 }
+
+; CHECK-LABEL: @multiphi
+; CHECK-LABEL: scalar.ph:
+; CHECK: %bc.resume.val = phi i32 [ %n.vec, %middle.block ], [ 0, %entry ]
+; CHECK-LABEL: for.end:
+; CHECK: %phi = phi i32 [ {{.*}}, %for.body ], [ %n.vec, %middle.block ]
+; CHECK: %phi2 = phi i32 [ {{.*}}, %for.body ], [ %n.vec, %middle.block ]
+; CHECK: store i32 %phi2, i32* %p
+; CHECK: ret i32 %phi
+define i32 @multiphi(i32 %k, i32* %p)  {
+entry:
+  br label %for.body
+
+for.body:
+  %inc.phi = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %inc = add nsw i32 %inc.phi, 1
+  %cmp = icmp eq i32 %inc, %k
+  br i1 %cmp, label %for.end, label %for.body
+
+for.end:
+  %phi = phi i32 [ %inc, %for.body ]
+  %phi2 = phi i32 [ %inc, %for.body ]
+  store i32 %phi2, i32* %p
+  ret i32 %phi
+}