Add the C99 hex-float assembly syntax to our extension document.

As Ben pointed out, GAS doesn't support this syntax so we should give at least
some warning that it might not be portable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188377 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/Extensions.rst b/docs/Extensions.rst
index 78ff874abf096877799d3933555e1b4cc48c8ffb..52dadc74e3595d6e85691895d32bd155768349a2 100644 (file)
--- a/docs/Extensions.rst
+++ b/docs/Extensions.rst
@@ -14,6 +14,19 @@ Introduction
 This document describes extensions to tools and formats LLVM seeks compatibility
 with.
 
+General Assembly Syntax
+===========================
+
+C99-style Hexadecimal Floating-point Constants
+----------------------------------------------
+
+LLVM's assemblers allow floating-point constants to be written in C99's
+hexadecimal format instead of decimal if desired.
+
+.. code-block:: gas
+  .section .data
+  .float 0x1c2.2ap3
+
 Machine-specific Assembly Syntax
 ================================