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LangRef: Clarify expected sNaN behavior for minnum/maxnum 

This matches the de-facto behavior based on constant folding
and the default lowering to fmin/fmax.

llvm-svn: 340762
This commit is contained in:
Matt Arsenault 2018-08-27 17:40:07 +00:00
parent a2f095f1a3
commit 937003cf22
1 changed files with 27 additions and 10 deletions
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37
llvm/docs/LangRef.rst
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@ -11472,13 +11472,22 @@ type.
Semantics:
""""""""""
Follows the IEEE-754 semantics for minNum, which also match for libm's
fmin.
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. 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.
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
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -11513,13 +11522,21 @@ type.
Semantics:
""""""""""
Follows the IEEE-754 semantics for maxNum, which also match for libm's
fmax.
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. 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.
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.copysign.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^