kawashima-fj created this revision.
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Explanations for options of floating point are updated to match the
`RenderFloatingPointOptions` function in
`clang/lib/Driver/ToolChains/Clang.cpp`.
Missing explanations are also added.
This patch is based on D138088 <https://reviews.llvm.org/D138088>, and assumes
D138109 <https://reviews.llvm.org/D138109> will be accepted.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D138117
Files:
clang/docs/UsersManual.rst
Index: clang/docs/UsersManual.rst
===================================================================
--- clang/docs/UsersManual.rst
+++ clang/docs/UsersManual.rst
@@ -1431,21 +1431,15 @@
This option implies:
* ``-fno-honor-infinities``
-
* ``-fno-honor-nans``
-
+ * ``-fapprox-func``
* ``-fno-math-errno``
-
* ``-ffinite-math-only``
-
* ``-fassociative-math``
-
* ``-freciprocal-math``
-
* ``-fno-signed-zeros``
-
* ``-fno-trapping-math``
-
+ * ``-fno-rounding-math``
* ``-ffp-contract=fast``
Note: ``-ffast-math`` causes ``crtfastmath.o`` to be linked with code. See
@@ -1454,30 +1448,24 @@
.. 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:
* ``-fhonor-infinities``
-
* ``-fhonor-nans``
-
- * ``-fmath-errno``
-
+ * ``-fno-approx-func``
* ``-fno-finite-math-only``
-
* ``-fno-associative-math``
-
* ``-fno-reciprocal-math``
-
* ``-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
@@ -1513,7 +1501,8 @@
* ``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
@@ -1522,6 +1511,7 @@
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
@@ -1569,11 +1559,19 @@
.. 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``.
@@ -1589,7 +1587,7 @@
.. 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
@@ -1605,24 +1603,48 @@
.. 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-trapping-math``
+ * ``-ffp-contract=fast``
+
+ ``-fno-unsafe-math-optimizations`` implies:
+
+ * ``-fno-approx-func``
+ * ``-fno-associative-math``
+ * ``-fno-reciprocal-math``
+ * ``-fsigned-zeroes``
+ * ``-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 in combination. 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`` also 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
@@ -1682,7 +1704,7 @@
* ``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
@@ -1696,6 +1718,7 @@
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
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