Refer to IEEE 754-2019 in langref instead of 2018 draft

[stuart]

Summary

The language reference refers to drafts of IEEE 754-2018, but the spec has now been published as IEEE 754-2019 with no further changes to the semantics in question. Update the language reference to refer to the actual standard, instead.

[stuart]

@hans, is it too late for this to be considered as a candidate for the 9.0.0 release?

[tlively]

LGTM, thanks!

[majnemer]

docs/LangRef.rst

2705

2019

12185

minNum -> minimumNumber

12194

2019

12235–12244

Ditto.

[stuart]

docs/LangRef.rst

2705

Excuse the naïve question, but is it now actually incorrect for us to say that we use the IEEE 754-2008 floating point formats, or is this just a matter of it being generally better to refer to the most recent revision of the standard?

12185

I believe that we should say minNum here, as this refers to the old IEEE 754-2008 minNum semantics, and not the new IEEE 754-2019 minumumNumber semantics. That is to say, the llvm.minnum.* intrinsics have been deliberately kept with the IEEE 754-2008 semantics, and new intrinsics named llvm.minimum.* have been added for IEEE 754-2019 semantics.

That said, IMO, this should be updated to refer to IEEE 754-2008 explicitly in all places.

If we intend to update the 9.0.0 docs, should this be part of the update?

12194

This should be left as IEEE 754-2008 as the intrinsic matches the semantics of the older standard.

12235–12244

Ditto.

[stuart]

docs/LangRef.rst

12185

Correction: I now realise that the new NaN-propagating operations in IEEE 754-2019 are actually named minimum and maximum, not minimumNumber and maximumNumber. We should explicitly mention the names of these operations in the documentation for the llvm.minimum.* and llvm.maximum.* intrinsics, below.

However, IEEE 754-2019 also adds "number-favoring" operations named minimumNumber and maximumNumber that are broadly the same as minNum and maxNum, but alter the semantics regarding sNaNs. I am not aware of the semantics for the llvm.minnum.* and llvm.maxnum.* intrinsics having been changed to those of the IEEE 754-2019 minimumNumber and maximumNumber operations, though, so I am still not certain of this change.

Should the llvm.minnum.* and llvm.maxnum.* intrinsics be documented as undefined as to whether they have the semantics of the either the IEEE 754-2008 minNum and maxNum operations or the IEEE 754-2019 minimumNumber and maximumNumber operations, or should this explicitly reference the semantics of the IEEE 754-2008 minNum and maxNum operations, or should this explicitly reference the semantics of the IEEE 754-2019 minimumNumber and maximumNumber operations?

If the change in this review is acceptable, then I would suggest that the changes for llvm.minnum.* and llvm.maxnum.* can be done in a subsequent review, but we do need to determine what changes will be required.

[hans]

In D67507#1668041, @stuart wrote:

@hans, is it too late for this to be considered as a candidate for the 9.0.0 release?

Yes, at this point I'd prefer not to merge anything that's not critical.

[uweigand]

Should the changes to llvm.minimum / llvm.maximum be applied now?

[RKSimon]

@stuart Any movement on this?

[qiucf]

Reverse ping..?

docs/LangRef.rst

.. list-table::
 
    * - ``x86_fp80``
      -  80-bit floating-point value (X87)
 
    * - ``ppc_fp128``
      - 128-bit floating-point value (two 64-bits)
 
 The binary format of half, float, double, and fp128 correspond to the
 IEEE-754-2008 specifications for binary16, binary32, binary64, and binary128
 respectively.
 
 X86_mmx Type
 """"""""""""
 
 :Overview:
 
 The x86_mmx type represents a value held in an MMX register on an x86

 """"""""""
 
 The arguments and return value are floating-point numbers of the same
 type.
 
 Semantics:
 """"""""""
 
 Follows the IEEE-754 semantics for minNum, except for handling of
 signaling NaNs. This match's the behavior of libm's fmin.
 
 If either operand is a NaN, returns the other non-NaN operand. Returns
 NaN only if both operands are NaN. The returned NaN is always
 quiet. If the operands compare equal, returns a value that compares
 equal to both operands. This means that fmin(+/-0.0, +/-0.0) could
 return either -0.0 or 0.0.
 
 Unlike the IEEE-754 2008 behavior, this does not distinguish between
 signaling and quiet NaN inputs. If a target's implementation follows
 the standard and returns a quiet NaN if either input is a signaling
 NaN, the intrinsic lowering is responsible for quieting the inputs to
 correctly return the non-NaN input (e.g. by using the equivalent of
 ``llvm.canonicalize``).
 
 
 '``llvm.maxnum.*``' Intrinsic

 Arguments:
 """"""""""
 
 The arguments and return value are floating-point numbers of the same
 type.
 
 Semantics:
 """"""""""
 Follows the IEEE-754 semantics for maxNum except for the handling of
 signaling NaNs. This matches the behavior of libm's fmax.
 
 If either operand is a NaN, returns the other non-NaN operand. Returns
 NaN only if both operands are NaN. The returned NaN is always
 quiet. If the operands compare equal, returns a value that compares
 equal to both operands. This means that fmax(+/-0.0, +/-0.0) could
 return either -0.0 or 0.0.
 
 Unlike the IEEE-754 2008 behavior, this does not distinguish between
 signaling and quiet NaN inputs. If a target's implementation follows
 the standard and returns a quiet NaN if either input is a signaling
 NaN, the intrinsic lowering is responsible for quieting the inputs to
 correctly return the non-NaN input (e.g. by using the equivalent of
 ``llvm.canonicalize``).
 
 '``llvm.minimum.*``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 
 The arguments and return value are floating-point numbers of the same
 type.
 
 Semantics:
 """"""""""
 If either operand is a NaN, returns NaN. Otherwise returns the lesser
 of the two arguments. -0.0 is considered to be less than +0.0 for this
-intrinsic. Note that these are the semantics specified in the draft of
-IEEE 754-2018.
+intrinsic. Note that these are the semantics specified in IEEE 754-2019.
 
 '``llvm.maximum.*``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Syntax:
 """""""
 
 This is an overloaded intrinsic. You can use ``llvm.maximum`` on any

 
 The arguments and return value are floating-point numbers of the same
 type.
 
 Semantics:
 """"""""""
 If either operand is a NaN, returns NaN. Otherwise returns the greater
 of the two arguments. -0.0 is considered to be less than +0.0 for this
-intrinsic. Note that these are the semantics specified in the draft of
-IEEE 754-2018.
+intrinsic. Note that these are the semantics specified in IEEE 754-2019.
 
 '``llvm.copysign.*``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Syntax:
 """""""
 
 This is an overloaded intrinsic. You can use ``llvm.copysign`` on any