Docs: Add --disable-arm64-crc32 description to INSTALL.

diff --git a/INSTALL b/INSTALL
index d6eaa616b207763e8b19ac9c01688c147e0dc35d..670e398981e38a63958b8feef83a9d09f58912ec 100644 (file)
--- a/INSTALL
+++ b/INSTALL
@@ -372,7 +372,7 @@ XZ Utils Installation
                 code.
 
     --disable-clmul-crc
-                Disable the use carryless multiplication for CRC
+                Disable the use of carryless multiplication for CRC
                 calculation even if compiler support for it is detected.
                 The code uses runtime detection of SSSE3, SSE4.1, and
                 CLMUL instructions on x86. On 32-bit x86 this currently
@@ -383,6 +383,16 @@ XZ Utils Installation
                 required extensions (-msse4.1 -mpclmul) then runtime
                 detection isn't used and the generic code is omitted.
 
+    --disable-arm64-crc32
+                Disable the use of the ARM64 CRC32 instruction extension
+                even if compiler support for it is detected. The code will
+                detect support for the instruction at runtime.
+
+                If using compiler options that unconditionally allow the
+                required extensions (-march=armv8-a+crc or -march=armv8.1-a
+                and later) then runtime detection isn't used and the
+                generic code is omitted.
+
     --enable-unaligned-access
                 Allow liblzma to use unaligned memory access for 16-bit,
                 32-bit, and 64-bit loads and stores. This should be