diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -8079,8 +8079,11 @@
 
   // If the target claims to have no vector registers don't attempt
   // vectorization.
-  if (!TTI->getNumberOfRegisters(TTI->getRegisterClassForType(true)))
+  if (!TTI->getNumberOfRegisters(TTI->getRegisterClassForType(true))) {
+    LLVM_DEBUG(
+        dbgs() << "SLP: Didn't find any vector registers for target, abort.\n");
     return false;
+  }
 
   // Don't vectorize when the attribute NoImplicitFloat is used.
   if (F.hasFnAttribute(Attribute::NoImplicitFloat))