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Diffstat (limited to 'llvm/docs/LangRef.rst')
| -rw-r--r-- | llvm/docs/LangRef.rst | 142 |
1 files changed, 86 insertions, 56 deletions
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index f6256e5143a..8cbed7d87d1 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -2272,11 +2272,11 @@ seq\_cst total orderings of other operations that are not marked Fast-Math Flags --------------- -LLVM IR floating-point binary ops (:ref:`fadd <i_fadd>`, +LLVM IR floating-point operations (:ref:`fadd <i_fadd>`, :ref:`fsub <i_fsub>`, :ref:`fmul <i_fmul>`, :ref:`fdiv <i_fdiv>`, :ref:`frem <i_frem>`, :ref:`fcmp <i_fcmp>`) and :ref:`call <i_call>` -instructions have the following flags that can be set to enable -otherwise unsafe floating point transformations. +may use the following flags to enable otherwise unsafe +floating-point transformations. ``nnan`` No NaNs - Allow optimizations to assume the arguments and result are not @@ -2300,10 +2300,17 @@ otherwise unsafe floating point transformations. Allow floating-point contraction (e.g. fusing a multiply followed by an addition into a fused multiply-and-add). +``afn`` + Approximate functions - Allow substitution of approximate calculations for + functions (sin, log, sqrt, etc). See floating-point intrinsic definitions + for places where this can apply to LLVM's intrinsic math functions. + +``reassoc`` + Allow reassociation transformations for floating-point instructions. + This may dramatically change results in floating point. + ``fast`` - Fast - Allow algebraically equivalent transformations that may - dramatically change results in floating point (e.g. reassociate). This - flag implies all the others. + This flag implies all of the others. .. _uselistorder: @@ -10483,7 +10490,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.sqrt`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10497,20 +10504,22 @@ all types however. Overview: """"""""" -The '``llvm.sqrt``' intrinsics return the square root of the specified value, -returning the same value as the libm '``sqrt``' functions would, but without -trapping or setting ``errno``. +The '``llvm.sqrt``' intrinsics return the square root of the specified value. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the square root of the operand if it is a nonnegative -floating point number. +Return the same value as a corresponding libm '``sqrt``' function but without +trapping or setting ``errno``. For types specified by IEEE-754, the result +matches a conforming libm implementation. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.powi.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10557,7 +10566,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.sin`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10576,14 +10585,16 @@ The '``llvm.sin.*``' intrinsics return the sine of the operand. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the sine of the specified operand, returning the -same values as the libm ``sin`` functions would, and handles error -conditions in the same way. +Return the same value as a corresponding libm '``sin``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.cos.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10592,7 +10603,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.cos`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10611,14 +10622,16 @@ The '``llvm.cos.*``' intrinsics return the cosine of the operand. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the cosine of the specified operand, returning the -same values as the libm ``cos`` functions would, and handles error -conditions in the same way. +Return the same value as a corresponding libm '``cos``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.pow.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10627,7 +10640,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.pow`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10647,15 +10660,16 @@ specified (positive or negative) power. Arguments: """""""""" -The second argument is a floating point power, and the first is a value -to raise to that power. +The arguments and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the first value raised to the second power, -returning the same values as the libm ``pow`` functions would, and -handles error conditions in the same way. +Return the same value as a corresponding libm '``pow``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.exp.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10664,7 +10678,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.exp`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10684,13 +10698,16 @@ value. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the same values as the libm ``exp`` functions -would, and handles error conditions in the same way. +Return the same value as a corresponding libm '``exp``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.exp2.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10699,7 +10716,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.exp2`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10719,13 +10736,16 @@ specified value. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the same values as the libm ``exp2`` functions -would, and handles error conditions in the same way. +Return the same value as a corresponding libm '``exp2``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.log.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10734,7 +10754,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.log`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10754,13 +10774,16 @@ value. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the same values as the libm ``log`` functions -would, and handles error conditions in the same way. +Return the same value as a corresponding libm '``log``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.log10.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10769,7 +10792,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.log10`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10789,13 +10812,16 @@ specified value. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the same values as the libm ``log10`` functions -would, and handles error conditions in the same way. +Return the same value as a corresponding libm '``log10``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.log2.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10804,7 +10830,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.log2`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10824,13 +10850,16 @@ value. Arguments: """""""""" -The argument and return value are floating point numbers of the same type. +The argument and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the same values as the libm ``log2`` functions -would, and handles error conditions in the same way. +Return the same value as a corresponding libm '``log2``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.fma.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -10839,7 +10868,7 @@ Syntax: """"""" This is an overloaded intrinsic. You can use ``llvm.fma`` on any -floating point or vector of floating point type. Not all targets support +floating-point or vector of floating-point type. Not all targets support all types however. :: @@ -10853,20 +10882,21 @@ all types however. Overview: """"""""" -The '``llvm.fma.*``' intrinsics perform the fused multiply-add -operation. +The '``llvm.fma.*``' intrinsics perform the fused multiply-add operation. Arguments: """""""""" -The argument and return value are floating point numbers of the same -type. +The arguments and return value are floating-point numbers of the same type. Semantics: """""""""" -This function returns the same values as the libm ``fma`` functions -would, and does not set errno. +Return the same value as a corresponding libm '``fma``' function but without +trapping or setting ``errno``. + +When specified with the fast-math-flag 'afn', the result may be approximated +using a less accurate calculation. '``llvm.fabs.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
