[docs][LangRef] Added minor update inside the `frem`. Fix : #61653

[aabhinavg]

Summary

Added minor update inside the frem. Fix : #61653

[aabhinavg]

done some minor fix

[RKSimon]

llvm/docs/LangRef.rst

9603

This doesn't seem to match with what you've added above - is x86 setting errno?

[aabhinavg]

llvm/docs/LangRef.rst

9603

the ‘frem’ instruction is commonly used in the implementation of mathematical functions in the standard C library, known as libm. The libm library provides a wide range of mathematical functions, such as trigonometric functions, logarithmic functions, exponential functions, and more.

The implementation of these functions often involves the use of the ‘frem’ instruction to calculate remainders, which are used in various computations. For example, the implementation of the trigonometric function ‘sine’ typically involves computing the remainder of the angle divided by 2π, which can be done using the ‘frem’ instruction.

Overall, the ‘frem’ instruction is a fundamental building block for many mathematical functions in libm and is a crucial part of many numerical computations in general.

‘frem’ instruction itself does not set ‘errno’ on x86 systems, but errors can be detected by checking the result of the instruction or examining the floating-point status flags.

[bchetioui]

Sorry for the delay in replying to this. I don't think that such implementation details belong in the documentation of the operation.
Is there a particular problem that would have been avoided by adding in this information?

[bchetioui]

Thanks!

I understand now that the intent behind the issue is that one may need to link libm in order to use frem, which was not obvious to me from the initial change.
I suggested an edit that conveys this more directly. Let me know what you think.

llvm/docs/LangRef.rst

9586–9589

Thanks for your patience. I propose the following rewrite for your change (or something to that effect). WDYT?

[bchetioui]

llvm/docs/LangRef.rst

9586–9589

Seems like I am missing a linefeed after the last line, please add that too :-)

[aabhinavg]

Done the required fix

[bchetioui]

Thank you, this looks good to me.

llvm/docs/LangRef.rst

 ::
 
       <result> = frem [fast-math flags]* <ty> <op1>, <op2>   ; yields ty:result
 
 Overview:
 """""""""
 
 The '``frem``' instruction returns the remainder from the division of
-its two operands.
+its two operands. On some target, such as X86, the instruction is 
+implemented as call to '``libm``' '``fmod``' function, but the 
+output is equivalent to the mathematical remainder.
+
 
 Arguments:
 """"""""""
 
 The two arguments to the '``frem``' instruction must be
 :ref:`floating-point <t_floating>` or :ref:`vector <t_vector>` of
 floating-point values. Both arguments must have identical types.
 
 Semantics:
 """"""""""
 
 The value produced is the floating-point remainder of the two operands.
 This is the same output as a libm '``fmod``' function, but without any
 possibility of setting ``errno``. The remainder has the same sign as the
 dividend.
 This instruction is assumed to execute in the default :ref:`floating-point
 environment <floatenv>`.
 This instruction can also take any number of :ref:`fast-math
 flags <fastmath>`, which are optimization hints to enable otherwise
 unsafe floating-point optimizations:
 
 Example: