[llvm] 6f3b360 - Revert "[ADT] Simplify getFirstEl (NFC)" (#153201)

[via llvm-commits]

Author: Benjamin Chetioui
Date: 2025-08-12T15:41:49Z
New Revision: 6f3b3604bcfd0b7aa398d2c5e3efb1d883f5a1d4

URL: https://github.com/llvm/llvm-project/commit/6f3b3604bcfd0b7aa398d2c5e3efb1d883f5a1d4
DIFF: https://github.com/llvm/llvm-project/commit/6f3b3604bcfd0b7aa398d2c5e3efb1d883f5a1d4.diff

LOG: Revert "[ADT] Simplify getFirstEl (NFC)" (#153201)

Reverts llvm/llvm-project#153127

This broke ubsan:
https://lab.llvm.org/buildbot/#/builders/25/builds/10649.

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/include/llvm/ADT/SmallVector.h b/llvm/include/llvm/ADT/SmallVector.h
index 6da519adcee6f..80f7734b86907 100644
--- a/llvm/include/llvm/ADT/SmallVector.h
+++ b/llvm/include/llvm/ADT/SmallVector.h
@@ -128,8 +128,8 @@ class SmallVectorTemplateCommon
   /// SmallVectorStorage is properly-aligned even for small-size of 0.
   void *getFirstEl() const {
     return const_cast<void *>(reinterpret_cast<const void *>(
-        reinterpret_cast<const SmallVectorAlignmentAndSize<T> *>(this)
-            ->FirstEl));
+        reinterpret_cast<const char *>(this) +
+        offsetof(SmallVectorAlignmentAndSize<T>, FirstEl)));
   }
   // Space after 'FirstEl' is clobbered, do not add any instance vars after it.