[clang] ba8b5ff - Adding a note about the macro __FLT_EVAL_METHOD__; NFC

[Aaron Ballman via cfe-commits]

Author: Zahira Ammarguellat
Date: 2022-08-23T14:35:57-04:00
New Revision: ba8b5ff874ad438a07ac3cc4f2bc75898b1401f8

URL: https://github.com/llvm/llvm-project/commit/ba8b5ff874ad438a07ac3cc4f2bc75898b1401f8
DIFF: https://github.com/llvm/llvm-project/commit/ba8b5ff874ad438a07ac3cc4f2bc75898b1401f8.diff

LOG: Adding a note about the macro __FLT_EVAL_METHOD__; NFC

This is to clarify that the macro __FLT_EVAL_METHOD__ is not pre-
defined like other preprocessor macros. It will not appear when
preprocessor macros are dumped.

Differential Revision: https://reviews.llvm.org/D124033

Added: 
    

Modified: 
    clang/docs/UsersManual.rst

Removed: 
    


################################################################################
diff  --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 78ccf4572ffc..883a0df32992 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1631,12 +1631,15 @@ Note that floating-point operations performed as part of constant initialization
 
 A note about ``__FLT_EVAL_METHOD__``
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-The macro ``__FLT_EVAL_METHOD__`` will expand to either the value set from the
-command line option ``ffp-eval-method`` or to the value from the target info
-setting. The ``__FLT_EVAL_METHOD__`` macro cannot expand to the correct
-evaluation method in the presence of a ``#pragma`` which alters the evaluation
-method. An error is issued if ``__FLT_EVAL_METHOD__`` is expanded inside a scope
-modified by ``#pragma clang fp eval_method``.
+The ``__FLT_EVAL_METHOD__`` is not defined as a traditional macro, and so it
+will not appear when dumping preprocessor macros. Instead, the value
+``__FLT_EVAL_METHOD__`` expands to is determined at the point of expansion
+either from the value set by the ``-ffp-eval-method`` command line option or
+from the target. This is because the ``__FLT_EVAL_METHOD__`` macro
+cannot expand to the correct evaluation method in the presence of a ``#pragma``
+which alters the evaluation method. An error is issued if
+``__FLT_EVAL_METHOD__`` is expanded inside a scope modified by
+``#pragma clang fp eval_method``.
 
 .. _fp-constant-eval: