From 6e9457fc4da9d77ec671ca594144aec8b9753321 Mon Sep 17 00:00:00 2001
From: Guillaume Chatelet <gchatelet@google.com>
Date: Mon, 6 Jul 2020 08:47:58 +0000
Subject: [PATCH] Fix off by one error in Bitfields

Differential Revision: https://reviews.llvm.org/D83192
---
 include/llvm/ADT/Bitfields.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/llvm/ADT/Bitfields.h b/include/llvm/ADT/Bitfields.h
index 2e38cca673e..68b1549a0ac 100644
--- a/include/llvm/ADT/Bitfields.h
+++ b/include/llvm/ADT/Bitfields.h
@@ -227,7 +227,7 @@ struct Bitfield {
     static constexpr unsigned Shift = Offset;
     static constexpr unsigned Bits = Size;
     static constexpr unsigned FirstBit = Offset;
-    static constexpr unsigned LastBit = Shift + Bits;
+    static constexpr unsigned LastBit = Shift + Bits - 1;
 
   private:
     template <typename, typename> friend struct bitfields_details::Impl;
@@ -273,7 +273,7 @@ struct Bitfield {
 
   /// Returns whether the two bitfields share common bits.
   template <typename A, typename B> static constexpr bool isOverlapping() {
-    return A::LastBit > B::FirstBit && B::LastBit > A::FirstBit;
+    return A::LastBit >= B::FirstBit && B::LastBit >= A::FirstBit;
   }
 };