From cd1e94d505f0d238b37f0012d53cc0e9bd2b44c9 Mon Sep 17 00:00:00 2001
From: Steven Johnson <srj@google.com>
Date: Fri, 7 Feb 2020 14:56:56 -0800
Subject: [PATCH] Forbid debug_to_file() on vectorized Funcs (Issue #4596)

---
 src/VectorizeLoops.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/VectorizeLoops.cpp b/src/VectorizeLoops.cpp
index 8ce087c9a8f2..af0c0f9de7a0 100644
--- a/src/VectorizeLoops.cpp
+++ b/src/VectorizeLoops.cpp
@@ -514,6 +514,10 @@ class VectorSubs : public IRMutator {
     }
 
     Expr visit(const Call *op) override {
+        user_assert(!op->is_intrinsic(Call::debug_to_file))
+            << "It is not legal to use debug_to_file() on a Func that is also vectorized. "
+            << "Try removing the .vectorize() directive(s).";
+
         // Widen the call by changing the lanes of all of its
         // arguments and its return type
         vector<Expr> new_args(op->args.size());