[llvm] 4c0a965 - Fix off by one error in Bitfields

[Guillaume Chatelet via llvm-commits]

Author: Guillaume Chatelet
Date: 2020-07-06T08:47:58Z
New Revision: 4c0a965c0926d5d6aa786a7de60f7939239099e3

URL: https://github.com/llvm/llvm-project/commit/4c0a965c0926d5d6aa786a7de60f7939239099e3
DIFF: https://github.com/llvm/llvm-project/commit/4c0a965c0926d5d6aa786a7de60f7939239099e3.diff

LOG: Fix off by one error in Bitfields

Differential Revision: https://reviews.llvm.org/D83192

Added: 
    

Modified: 
    llvm/include/llvm/ADT/Bitfields.h

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/Bitfields.h b/llvm/include/llvm/ADT/Bitfields.h
index 2e38cca673ea..68b1549a0ac5 100644
--- a/llvm/include/llvm/ADT/Bitfields.h
+++ b/llvm/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;
   }
 };