1 files changed, 31 insertions, 0 deletions
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 9c64b046377..6f66c4d04d9 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1111,6 +1111,37 @@ are listed below.
    This option restricts the generated code to use general registers
    only. This only applies to the AArch64 architecture.
 
+**-f[no-]max-unknown-pointer-align=[number]**
+   Instruct the code generator to not enforce a higher alignment than the given
+   number (of bytes) when accessing memory via an opaque pointer or reference.
+   This cap is ignored when directly accessing a variable or when the pointee
+   type has an explicit “aligned” attribute.
+
+   The value should usually be determined by the properties of the system allocator.
+   Some builtin types, especially vector types, have very high natural alignments;
+   when working with values of those types, Clang usually wants to use instructions
+   that take advantage of that alignment.  However, many system allocators do
+   not promise to return memory that is more than 8-byte or 16-byte-aligned.  Use
+   this option to limit the alignment that the compiler can assume for an arbitrary
+   pointer, which may point onto the heap.
+
+   This option does not affect the ABI alignment of types; the layout of structs and
+   unions and the value returned by the alignof operator remain the same.
+
+   This option can be overridden on a case-by-case basis by putting an explicit
+   “aligned” alignment on a struct, union, or typedef.  For example:
+
+   .. code-block:: console
+
+      #include <immintrin.h>
+      // Make an aligned typedef of the AVX-512 16-int vector type.
+      typedef __v16si __aligned_v16si __attribute__((aligned(64)));
+
+      void initialize_vector(__aligned_v16si *v) {
+        // The compiler may assume that ‘v’ is 64-byte aligned, regardless of the
+        // value of -fmax-unknown-pointer-align.
+      }
+
 
 Profile Guided Optimization
 ---------------------------