diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1437,6 +1437,8 @@
 
    * ``-fno-honor-nans``
 
+   * ``-fapprox-func``
+
    * ``-fno-math-errno``
 
    * ``-ffinite-math-only``
@@ -1449,6 +1451,8 @@
 
    * ``-fno-trapping-math``
 
+   * ``-fno-rounding-math``
+
    * ``-ffp-contract=fast``
 
    Note: ``-ffast-math`` causes ``crtfastmath.o`` to be linked with code. See
@@ -1457,7 +1461,7 @@
 .. option:: -fno-fast-math
 
    Disable fast-math mode.  This options disables unsafe floating-point
-   optimizations by preventing the compiler from making any tranformations that
+   optimizations by preventing the compiler from making any transformations that
    could affect the results.
 
    This option implies:
@@ -1466,7 +1470,7 @@
 
    * ``-fhonor-nans``
 
-   * ``-fmath-errno``
+   * ``-fno-approx-func``
 
    * ``-fno-finite-math-only``
 
@@ -1476,14 +1480,15 @@
 
    * ``-fsigned-zeros``
 
-   * ``-fno-trapping-math``
-
    * ``-ffp-contract=on``
 
-   * ``-fdenormal-fp-math=ieee``
+   Also, this option resets following options to their target-dependent defaults.
+
+   * ``-f[no-]math-errno``
+   * ``-fdenormal-fp-math=<value>``
 
    There is ambiguity about how ``-ffp-contract``, ``-ffast-math``,
-   and ``-fno-fast-math`` behave in combination. To keep the value of
+   and ``-fno-fast-math`` behave when combined. To keep the value of
    ``-ffp-contract`` consistent, we define this set of rules:
 
    * ``-ffast-math`` sets ``ffp-contract`` to ``fast``.
@@ -1516,7 +1521,8 @@
    * ``preserve-sign`` - the sign of a flushed-to-zero number is preserved in the sign of 0
    * ``positive-zero`` - denormals are flushed to positive zero
 
-   Defaults to ``ieee``.
+   The default value depends on the target. For most targets, defaults to
+   ``ieee``.
 
 .. option:: -f[no-]strict-float-cast-overflow
 
@@ -1525,6 +1531,7 @@
    By default, Clang will not guarantee any particular result in that case.
    With the 'no-strict' option, Clang will saturate towards the smallest and
    largest representable integer values instead. NaNs will be converted to zero.
+   Defaults to ``-fstrict-float-cast-overflow``.
 
 .. option:: -f[no-]math-errno
 
@@ -1572,11 +1579,19 @@
 
 .. option:: -f[no-]honor-infinities
 
+   Allow floating-point optimizations that assume arguments and results are
+   not +-Inf.
+   Defaults to ``-fhonor-infinities``.
+
    If both ``-fno-honor-infinities`` and ``-fno-honor-nans`` are used,
    has the same effect as specifying ``-ffinite-math-only``.
 
 .. option:: -f[no-]honor-nans
 
+   Allow floating-point optimizations that assume arguments and results are
+   not NaNs.
+   Defaults to ``-fhonor-nans``.
+
    If both ``-fno-honor-infinities`` and ``-fno-honor-nans`` are used,
    has the same effect as specifying ``-ffinite-math-only``.
 
@@ -1592,7 +1607,7 @@
 .. option:: -f[no-]signed-zeros
 
    Allow optimizations that ignore the sign of floating point zeros.
-   Defaults to ``-fno-signed-zeros``.
+   Defaults to ``-fsigned-zeros``.
 
 .. option:: -f[no-]associative-math
 
@@ -1608,24 +1623,48 @@
 
 .. option:: -f[no-]unsafe-math-optimizations
 
-   Allow unsafe floating-point optimizations. Also implies:
+   Allow unsafe floating-point optimizations.
+   ``-funsafe-math-optimizations`` also implies:
 
+   * ``-fapprox-func``
    * ``-fassociative-math``
    * ``-freciprocal-math``
-   * ``-fno-signed-zeroes``
-   * ``-fno-trapping-math``.
+   * ``-fno-signed-zeros``
+   * ``-fno-trapping-math``
+   * ``-ffp-contract=fast``
+
+   ``-fno-unsafe-math-optimizations`` implies:
+
+   * ``-fno-approx-func``
+   * ``-fno-associative-math``
+   * ``-fno-reciprocal-math``
+   * ``-fsigned-zeros``
+   * ``-ftrapping-math``
+   * ``-ffp-contract=on``
+   * ``-fdenormal-fp-math=ieee``
+
+   There is ambiguity about how ``-ffp-contract``,
+   ``-funsafe-math-optimizations``, and ``-fno-unsafe-math-optimizations``
+   behave when combined. Explanation in :option:`-fno-fast-math` also applies
+   to these options.
 
    Defaults to ``-fno-unsafe-math-optimizations``.
 
 .. option:: -f[no-]finite-math-only
 
    Allow floating-point optimizations that assume arguments and results are
-   not NaNs or +-Inf.  This defines the ``__FINITE_MATH_ONLY__`` preprocessor macro.
-   Also implies:
+   not NaNs or +-Inf. ``-ffinite-math-only`` defines the
+   ``__FINITE_MATH_ONLY__`` preprocessor macro.
+   ``-ffinite-math-only`` implies:
 
    * ``-fno-honor-infinities``
    * ``-fno-honor-nans``
 
+   ``-ffno-inite-math-only`` implies:
+
+   * ``-fhonor-infinities``
+   * ``-fhonor-nans``
+
    Defaults to ``-fno-finite-math-only``.
 
 .. option:: -f[no-]rounding-math
@@ -1685,7 +1724,7 @@
    * ``double`` The compiler uses ``double`` as the floating-point evaluation method for all float expressions of type that is narrower than ``double``.
    * ``extended`` The compiler uses ``long double`` as the floating-point evaluation method for all float expressions of type that is narrower than ``long double``.
 
-.. option:: -f[no-]protect-parens:
+.. option:: -f[no-]protect-parens
 
    This option pertains to floating-point types, complex types with
    floating-point components, and vectors of these types. Some arithmetic
@@ -1699,6 +1738,7 @@
    additions in any order regardless of the parentheses. When enabled, this
    option forces the optimizer to honor the order of operations with respect
    to parentheses in all circumstances.
+   Defaults to ``-fno-protect-parens``.
 
    Note that floating-point contraction (option `-ffp-contract=`) is disabled
    when `-fprotect-parens` is enabled.  Also note that in safe floating-point