From ec3f24d4538d1c262377331c7b35ea66e023cf98 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Wed, 30 Sep 2020 11:13:54 +0100
Subject: [PATCH] [InstCombine] recognizeBSwapOrBitReverseIdiom - assert for
 correct bit providence indices. NFCI.

As suggested by @spatel on D88316
---
 llvm/lib/Transforms/Utils/Local.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 61f4dffb641c..8ff11ba4cab4 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -3027,6 +3027,9 @@ bool llvm::recognizeBSwapOrBitReverseIdiom(
   if (!Res)
     return false;
   auto &BitProvenance = Res->Provenance;
+  assert(all_of(BitProvenance,
+                [](int8_t I) { return I == BitPart::Unset || 0 <= I; }) &&
+         "Illegal bit provenance index");
 
   // Now, is the bit permutation correct for a bswap or a bitreverse? We can
   // only byteswap values with an even number of bytes.