[clang][docs] Correct floating point option explanations
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. Differential Revision: https://reviews.llvm.org/D138117
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KAWASHIMA Takahiro
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@ -1437,6 +1437,8 @@ floating point semantic models: precise (the default), strict, and fast.
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* ``-fno-honor-nans``
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* ``-fapprox-func``
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* ``-fno-math-errno``
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* ``-ffinite-math-only``
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@ -1449,6 +1451,8 @@ floating point semantic models: precise (the default), strict, and fast.
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* ``-fno-trapping-math``
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* ``-fno-rounding-math``
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* ``-ffp-contract=fast``
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Note: ``-ffast-math`` causes ``crtfastmath.o`` to be linked with code. See
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@ -1457,7 +1461,7 @@ floating point semantic models: precise (the default), strict, and fast.
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.. option:: -fno-fast-math
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Disable fast-math mode. This options disables unsafe floating-point
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optimizations by preventing the compiler from making any tranformations that
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optimizations by preventing the compiler from making any transformations that
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could affect the results.
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This option implies:
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@ -1466,7 +1470,7 @@ floating point semantic models: precise (the default), strict, and fast.
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* ``-fhonor-nans``
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* ``-fmath-errno``
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* ``-fno-approx-func``
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* ``-fno-finite-math-only``
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@ -1476,14 +1480,15 @@ floating point semantic models: precise (the default), strict, and fast.
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* ``-fsigned-zeros``
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* ``-fno-trapping-math``
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* ``-ffp-contract=on``
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* ``-fdenormal-fp-math=ieee``
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Also, this option resets following options to their target-dependent defaults.
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* ``-f[no-]math-errno``
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* ``-fdenormal-fp-math=<value>``
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There is ambiguity about how ``-ffp-contract``, ``-ffast-math``,
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and ``-fno-fast-math`` behave in combination. To keep the value of
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and ``-fno-fast-math`` behave when combined. To keep the value of
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``-ffp-contract`` consistent, we define this set of rules:
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* ``-ffast-math`` sets ``ffp-contract`` to ``fast``.
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@ -1516,7 +1521,8 @@ floating point semantic models: precise (the default), strict, and fast.
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* ``preserve-sign`` - the sign of a flushed-to-zero number is preserved in the sign of 0
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* ``positive-zero`` - denormals are flushed to positive zero
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Defaults to ``ieee``.
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The default value depends on the target. For most targets, defaults to
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``ieee``.
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.. option:: -f[no-]strict-float-cast-overflow
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@ -1525,6 +1531,7 @@ floating point semantic models: precise (the default), strict, and fast.
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By default, Clang will not guarantee any particular result in that case.
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With the 'no-strict' option, Clang will saturate towards the smallest and
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largest representable integer values instead. NaNs will be converted to zero.
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Defaults to ``-fstrict-float-cast-overflow``.
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.. option:: -f[no-]math-errno
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@ -1572,11 +1579,19 @@ floating point semantic models: precise (the default), strict, and fast.
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.. option:: -f[no-]honor-infinities
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Allow floating-point optimizations that assume arguments and results are
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not +-Inf.
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Defaults to ``-fhonor-infinities``.
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If both ``-fno-honor-infinities`` and ``-fno-honor-nans`` are used,
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has the same effect as specifying ``-ffinite-math-only``.
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.. option:: -f[no-]honor-nans
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Allow floating-point optimizations that assume arguments and results are
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not NaNs.
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Defaults to ``-fhonor-nans``.
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If both ``-fno-honor-infinities`` and ``-fno-honor-nans`` are used,
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has the same effect as specifying ``-ffinite-math-only``.
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@ -1592,7 +1607,7 @@ floating point semantic models: precise (the default), strict, and fast.
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.. option:: -f[no-]signed-zeros
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Allow optimizations that ignore the sign of floating point zeros.
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Defaults to ``-fno-signed-zeros``.
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Defaults to ``-fsigned-zeros``.
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.. option:: -f[no-]associative-math
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@ -1608,24 +1623,48 @@ floating point semantic models: precise (the default), strict, and fast.
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.. option:: -f[no-]unsafe-math-optimizations
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Allow unsafe floating-point optimizations. Also implies:
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Allow unsafe floating-point optimizations.
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``-funsafe-math-optimizations`` also implies:
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* ``-fapprox-func``
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* ``-fassociative-math``
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* ``-freciprocal-math``
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* ``-fno-signed-zeroes``
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* ``-fno-trapping-math``.
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* ``-fno-signed-zeros``
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* ``-fno-trapping-math``
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* ``-ffp-contract=fast``
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``-fno-unsafe-math-optimizations`` implies:
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* ``-fno-approx-func``
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* ``-fno-associative-math``
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* ``-fno-reciprocal-math``
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* ``-fsigned-zeros``
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* ``-ftrapping-math``
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* ``-ffp-contract=on``
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* ``-fdenormal-fp-math=ieee``
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There is ambiguity about how ``-ffp-contract``,
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``-funsafe-math-optimizations``, and ``-fno-unsafe-math-optimizations``
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behave when combined. Explanation in :option:`-fno-fast-math` also applies
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to these options.
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Defaults to ``-fno-unsafe-math-optimizations``.
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.. option:: -f[no-]finite-math-only
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Allow floating-point optimizations that assume arguments and results are
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not NaNs or +-Inf. This defines the ``__FINITE_MATH_ONLY__`` preprocessor macro.
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Also implies:
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not NaNs or +-Inf. ``-ffinite-math-only`` defines the
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``__FINITE_MATH_ONLY__`` preprocessor macro.
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``-ffinite-math-only`` implies:
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* ``-fno-honor-infinities``
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* ``-fno-honor-nans``
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``-ffno-inite-math-only`` implies:
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* ``-fhonor-infinities``
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* ``-fhonor-nans``
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Defaults to ``-fno-finite-math-only``.
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.. option:: -f[no-]rounding-math
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@ -1685,7 +1724,7 @@ floating point semantic models: precise (the default), strict, and fast.
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* ``double`` The compiler uses ``double`` as the floating-point evaluation method for all float expressions of type that is narrower than ``double``.
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* ``extended`` The compiler uses ``long double`` as the floating-point evaluation method for all float expressions of type that is narrower than ``long double``.
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.. option:: -f[no-]protect-parens:
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.. option:: -f[no-]protect-parens
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This option pertains to floating-point types, complex types with
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floating-point components, and vectors of these types. Some arithmetic
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@ -1699,6 +1738,7 @@ floating point semantic models: precise (the default), strict, and fast.
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additions in any order regardless of the parentheses. When enabled, this
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option forces the optimizer to honor the order of operations with respect
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to parentheses in all circumstances.
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Defaults to ``-fno-protect-parens``.
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Note that floating-point contraction (option `-ffp-contract=`) is disabled
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when `-fprotect-parens` is enabled. Also note that in safe floating-point
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