[llvm] [ADT] Tighten static_assert in Bitfields (PR #165099)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>

This patch tightens the static_assert.  FirstBit and LastBit are
0-based bit indices of a bitfield, so they must be strictly less than
StorageBits.


---
Full diff: https://github.com/llvm/llvm-project/pull/165099.diff


1 Files Affected:

- (modified) llvm/include/llvm/ADT/Bitfields.h (+2-2) 


``````````diff
diff --git a/llvm/include/llvm/ADT/Bitfields.h b/llvm/include/llvm/ADT/Bitfields.h
index 1fbc41c472581..be9546e9cc4cb 100644
--- a/llvm/include/llvm/ADT/Bitfields.h
+++ b/llvm/include/llvm/ADT/Bitfields.h
@@ -100,8 +100,8 @@ template <typename Bitfield, typename StorageType> struct Impl {
   using IntegerType = typename Bitfield::IntegerType;
 
   static constexpr size_t StorageBits = sizeof(StorageType) * CHAR_BIT;
-  static_assert(Bitfield::FirstBit <= StorageBits, "Data must fit in mask");
-  static_assert(Bitfield::LastBit <= StorageBits, "Data must fit in mask");
+  static_assert(Bitfield::FirstBit < StorageBits, "Data must fit in mask");
+  static_assert(Bitfield::LastBit < StorageBits, "Data must fit in mask");
   static constexpr StorageType LowMask =
       maskTrailingOnes<StorageType>(Bitfield::Bits);
   static constexpr StorageType Mask = LowMask << Bitfield::Shift;

``````````

</details>


https://github.com/llvm/llvm-project/pull/165099