[llvm] LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN and signed zero (PR #112852)
YunQiang Su via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 21 17:47:06 PST 2025
https://github.com/wzssyqa updated https://github.com/llvm/llvm-project/pull/112852
>From 754c3e920f4fe6ab1311a98d735febfb460d6d03 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Fri, 18 Oct 2024 16:16:43 +0800
Subject: [PATCH 01/14] LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN
The documents claims that it ignores sNaN, while in the code it may
be different.
- as the finally callback, it use libc call fmin(3)/fmax(3).
while C23 clarify that fmin(3)/fmax(3) should return NaN for sNaN vs NUM.
- on some architectures, such as aarch64, it converts to `fmaxnm`,
which returns qNaN for sNaN vs NUM.
- on RISC-V (SPEC 2019+), it converts to `fmax`, which returns NUM
for sNaN vs NUM.
Since we have introduced llvm.minimumnum and llvm.maximumnum, which
follow IEEE 754-2019's minimumNumber/maximumNumber.
So, it's time for use to clarify llvm.minnum and llvm.maxnum.
Let's define it to the libc's defination.
---
llvm/docs/LangRef.rst | 75 ++++++++++++++++++-------------------------
1 file changed, 31 insertions(+), 44 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 8cc9036d1b67f6..47530b9e2c15b6 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16723,21 +16723,13 @@ type.
Semantics:
""""""""""
+Follows the IEEE754 2008 semantics for minNum, except for handling of
++0.0 vs -0.0. This matches the behavior of 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 either one of the operands. For example, this means that
-fmin(+0.0, -0.0) returns either operand.
-
-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``).
+If either operand is a qNaN, returns the other non-NaN operand. Returns
+NaN only if both operands are NaN or either operand is sNaN.
+If the operands compare equal, returns either one of the operands.
+For example, this means that fmin(+0.0, -0.0) returns either operand.
.. _i_maxnum:
@@ -16774,20 +16766,13 @@ type.
Semantics:
""""""""""
-Follows the IEEE-754 semantics for maxNum except for the handling of
-signaling NaNs. This matches the behavior of libm's fmax.
+Follows the IEEE754 2008 semantics for maxNum, except for handling of
++0.0 vs -0.0. 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 either one of the operands. For example, this means that
-fmax(+0.0, -0.0) returns 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``).
+NaN only if both operands are NaN or either operand is sNaN.
+If the operands compare equal, returns either one of the operands.
+For example, this means that fmin(+0.0, -0.0) returns either operand.
.. _i_minimum:
@@ -19666,12 +19651,12 @@ The '``llvm.vector.reduce.fmax.*``' intrinsics do a floating-point
matches the element-type of the vector input.
This instruction has the same comparison semantics as the '``llvm.maxnum.*``'
-intrinsic. That is, the result will always be a number unless all elements of
-the vector are NaN. For a vector with maximum element magnitude 0.0 and
-containing both +0.0 and -0.0 elements, the sign of the result is unspecified.
+intrinsic. If the intrinsic call has the ``nnan`` fast-math flag, then the
+operation can assume that NaNs are not present in the input vector.
-If the intrinsic call has the ``nnan`` fast-math flag, then the operation can
-assume that NaNs are not present in the input vector.
+It is deprecated, since the different order of inputs may produce different
+outputs, and it is hard to optimize with Vector or SIMD extensions.
+Use '``llvm.vector.reduce.fmaximum``' or '``llvm.vector.reduce.fmaximumnum``' instead.
Arguments:
""""""""""
@@ -19699,12 +19684,12 @@ The '``llvm.vector.reduce.fmin.*``' intrinsics do a floating-point
matches the element-type of the vector input.
This instruction has the same comparison semantics as the '``llvm.minnum.*``'
-intrinsic. That is, the result will always be a number unless all elements of
-the vector are NaN. For a vector with minimum element magnitude 0.0 and
-containing both +0.0 and -0.0 elements, the sign of the result is unspecified.
+intrinsic. If the intrinsic call has the ``nnan`` fast-math flag, then the
+operation can assume that NaNs are not present in the input vector.
-If the intrinsic call has the ``nnan`` fast-math flag, then the operation can
-assume that NaNs are not present in the input vector.
+It is deprecated, since the different order of inputs may produce different
+outputs, and it is hard to optimize with Vector or SIMD extensions.
+Use '``llvm.vector.reduce.fminimum``' or '``llvm.vector.reduce.fminimumnum``' instead.
Arguments:
""""""""""
@@ -23318,13 +23303,14 @@ result type. If only ``nnan`` is set then the neutral value is ``-Infinity``.
This instruction has the same comparison semantics as the
:ref:`llvm.vector.reduce.fmax <int_vector_reduce_fmax>` intrinsic (and thus the
-'``llvm.maxnum.*``' intrinsic). That is, the result will always be a number
-unless all elements of the vector and the starting value are ``NaN``. For a
-vector with maximum element magnitude ``0.0`` and containing both ``+0.0`` and
-``-0.0`` elements, the sign of the result is unspecified.
+'``llvm.maxnum.*``' intrinsic).
To ignore the start value, the neutral value can be used.
+It is deprecated, since the different order of inputs may produce different
+outputs, and it is hard to optimize with Vector or SIMD extensions.
+Use '``llvm.vp.vector.reduce.fmaximum``' or '``llvm.vp.vector.reduce.fmaximumnum``' instead.
+
Examples:
"""""""""
@@ -23388,13 +23374,14 @@ result type. If only ``nnan`` is set then the neutral value is ``+Infinity``.
This instruction has the same comparison semantics as the
:ref:`llvm.vector.reduce.fmin <int_vector_reduce_fmin>` intrinsic (and thus the
-'``llvm.minnum.*``' intrinsic). That is, the result will always be a number
-unless all elements of the vector and the starting value are ``NaN``. For a
-vector with maximum element magnitude ``0.0`` and containing both ``+0.0`` and
-``-0.0`` elements, the sign of the result is unspecified.
+'``llvm.minnum.*``' intrinsic).
To ignore the start value, the neutral value can be used.
+It is deprecated, since the different order of inputs may produce different
+outputs, and it is hard to optimize with Vector or SIMD extensions.
+Use '``llvm.vp.vector.reduce.fminimum``' or '``llvm.vp.vector.reduce.fminimumnum``' instead.
+
Examples:
"""""""""
>From 1a1069ccde7a7e4a3ed05334b9796900d6f1494a Mon Sep 17 00:00:00 2001
From: YunQiang Su <wzssyqa at gmail.com>
Date: Sat, 19 Oct 2024 01:33:13 +0800
Subject: [PATCH 02/14] minNum doesn't care about +0 vs -0
---
llvm/docs/LangRef.rst | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 47530b9e2c15b6..9c54b316257b34 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16723,8 +16723,8 @@ type.
Semantics:
""""""""""
-Follows the IEEE754 2008 semantics for minNum, except for handling of
-+0.0 vs -0.0. This matches the behavior of libm's fmin.
+Follows the IEEE754 2008 semantics for minNum.
+This also matches the behavior of libm's fmin.
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
@@ -16766,8 +16766,8 @@ type.
Semantics:
""""""""""
-Follows the IEEE754 2008 semantics for maxNum, except for handling of
-+0.0 vs -0.0. This matches the behavior of libm's fmax.
+Follows the IEEE754 2008 semantics for maxNum.
+This also 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 or either operand is sNaN.
>From c5b618d5cfa108809b1a899178a4070faded73e5 Mon Sep 17 00:00:00 2001
From: YunQiang Su <syq at debian.org>
Date: Sun, 20 Oct 2024 12:13:21 +0800
Subject: [PATCH 03/14] add history about libm
---
llvm/docs/LangRef.rst | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 9c54b316257b34..59f40b42fb31eb 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16724,7 +16724,11 @@ type.
Semantics:
""""""""""
Follows the IEEE754 2008 semantics for minNum.
-This also matches the behavior of libm's fmin.
+This also matches the current (C23) behavior of libm's fmin.
+
+Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
+sNaN for qNaN vs sNaN. Withe recent libc versions, libc follows IEEE754-2008:
+NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
@@ -16767,7 +16771,11 @@ type.
Semantics:
""""""""""
Follows the IEEE754 2008 semantics for maxNum.
-This also matches the behavior of libm's fmax.
+This also matches the current (C23) behavior of libm's fmax.
+
+Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
+sNaN for qNaN vs sNaN. Withe recent libc versions, libc follows IEEE754-2008:
+NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
If either operand is a NaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
>From 16bf3633321f096ef83cc10ffb3e67652f8d3f22 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Mon, 21 Oct 2024 08:56:22 +0800
Subject: [PATCH 04/14] fmin requires +0>-0
---
llvm/docs/LangRef.rst | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 59f40b42fb31eb..cc2258df3dc2a7 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16679,7 +16679,7 @@ versions of the intrinsics respect the exception behavior.
- qNaN, invalid exception
* - ``+0.0 vs -0.0``
- - either one
+ - +0.0(max)/-0.0(min)
- +0.0(max)/-0.0(min)
- +0.0(max)/-0.0(min)
@@ -16723,8 +16723,14 @@ type.
Semantics:
""""""""""
-Follows the IEEE754 2008 semantics for minNum.
-This also matches the current (C23) behavior of libm's fmin.
+Follows the IEEE754 2008 semantics for minNum with +0.0>-0.0.
+This is more strict than current (C23) behavior of libm's fmin.
+Some applications like Clang, can call '``llvm.minnum.*``' with '``nsz``' attribute
+to archive the same behaivor of libm's fmin.
+
+For some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, they have the
+strict same instructions; thus it is quite simple for these architectures.
+For other architectures, the custom or expand methods may provide '``nsz``' flavor.
Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
sNaN for qNaN vs sNaN. Withe recent libc versions, libc follows IEEE754-2008:
@@ -16770,12 +16776,14 @@ type.
Semantics:
""""""""""
-Follows the IEEE754 2008 semantics for maxNum.
-This also matches the current (C23) behavior of libm's fmax.
+Follows the IEEE754 2008 semantics for maxNum with +0.0>-0.0.
+This is more strict than current (C23) behavior of libm's fmax.
+Some applications like Clang, can call '``llvm.maxnum.*``' with '``nsz``' attribute
+to archive the same behaivor of libm's fmax.
-Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
-sNaN for qNaN vs sNaN. Withe recent libc versions, libc follows IEEE754-2008:
-NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
+For some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, they have the
+strict same instructions; thus it is quite simple for these architectures.
+For other architectures, the custom or expand methods may provide '``nsz``' flavor.
If either operand is a NaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
>From 1da6c90b656f2f640cd4eb09417d1e8e1c86e3f3 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Mon, 21 Oct 2024 09:11:35 +0800
Subject: [PATCH 05/14] some fix
---
llvm/docs/LangRef.rst | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index cc2258df3dc2a7..8edd4613dda85a 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16729,17 +16729,16 @@ Some applications like Clang, can call '``llvm.minnum.*``' with '``nsz``' attrib
to archive the same behaivor of libm's fmin.
For some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, they have the
-strict same instructions; thus it is quite simple for these architectures.
+strictly same instructions; thus it is quite simple for these architectures.
For other architectures, the custom or expand methods may provide '``nsz``' flavor.
Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
-sNaN for qNaN vs sNaN. Withe recent libc versions, libc follows IEEE754-2008:
+sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
If the operands compare equal, returns either one of the operands.
-For example, this means that fmin(+0.0, -0.0) returns either operand.
.. _i_maxnum:
@@ -16782,13 +16781,16 @@ Some applications like Clang, can call '``llvm.maxnum.*``' with '``nsz``' attrib
to archive the same behaivor of libm's fmax.
For some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, they have the
-strict same instructions; thus it is quite simple for these architectures.
+strictly same instructions; thus it is quite simple for these architectures.
For other architectures, the custom or expand methods may provide '``nsz``' flavor.
+Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
+sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
+NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
+
If either operand is a NaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
If the operands compare equal, returns either one of the operands.
-For example, this means that fmin(+0.0, -0.0) returns either operand.
.. _i_minimum:
>From 94bb3b53a644671cfddcdbbe2643496fc43e2bdf Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Wed, 23 Oct 2024 09:25:07 +0800
Subject: [PATCH 06/14] add inconsistent note
---
llvm/docs/LangRef.rst | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 8edd4613dda85a..1d908282ccb6e0 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16736,6 +16736,11 @@ Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
+Note that that arithmetic on an sNaN doesn't consistently produce a qNaN,
+so arithmetic feeding into a minnum can produce inconsistent results.
+Such as `fmin(sNaN+0.0, 1.0)` can produce qNaN or 1.0 depending on whether `+0.0`
+is optimized out.
+
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
If the operands compare equal, returns either one of the operands.
@@ -16788,6 +16793,11 @@ Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
+Note that that arithmetic on an sNaN doesn't consistently produce a qNaN,
+so arithmetic feeding into a maxnum can produce inconsistent results.
+Such as `fmax(sNaN+0.0, 1.0)` can produce qNaN or 1.0 depending on whether `+0.0`
+is optimized out.
+
If either operand is a NaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
If the operands compare equal, returns either one of the operands.
>From fb566b4cf5f2f01840b5278ecfd0f98fcb2e8368 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Wed, 30 Oct 2024 19:23:17 +0800
Subject: [PATCH 07/14] do more clarify
---
llvm/docs/LangRef.rst | 46 ++++++++++++++++----------
llvm/include/llvm/CodeGen/ISDOpcodes.h | 17 +++++++---
2 files changed, 40 insertions(+), 23 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 1d908282ccb6e0..77745601dd3618 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16723,12 +16723,21 @@ type.
Semantics:
""""""""""
-Follows the IEEE754 2008 semantics for minNum with +0.0>-0.0.
-This is more strict than current (C23) behavior of libm's fmin.
-Some applications like Clang, can call '``llvm.minnum.*``' with '``nsz``' attribute
-to archive the same behaivor of libm's fmin.
+Follows the IEEE-754 semantics for minNum, except that -0.0 < +0.0 for the purposes
+of this intrinsic. As for signaling NaNs, per the IEEE-754 semantics, if either operand
+is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
+function fmin, although not all implementations have implemented these recommended behaviors.
-For some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, they have the
+If either operand is a qNaN, returns the other non-NaN operand. Returns
+NaN only if both operands are NaN or either operand is sNaN.
+
+If the operands compare equal, returns either one of the operands.
+
+Returns -0.0 for +0.0 vs -0.0. libm doesn't require it, so that
+some applications like Clang, can call '``llvm.minnum.*``' with '``nsz``' attribute
+to archive the required behaivors of libm's fmin.
+
+Some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have the
strictly same instructions; thus it is quite simple for these architectures.
For other architectures, the custom or expand methods may provide '``nsz``' flavor.
@@ -16741,10 +16750,6 @@ so arithmetic feeding into a minnum can produce inconsistent results.
Such as `fmin(sNaN+0.0, 1.0)` can produce qNaN or 1.0 depending on whether `+0.0`
is optimized out.
-If either operand is a qNaN, returns the other non-NaN operand. Returns
-NaN only if both operands are NaN or either operand is sNaN.
-If the operands compare equal, returns either one of the operands.
-
.. _i_maxnum:
'``llvm.maxnum.*``' Intrinsic
@@ -16780,12 +16785,21 @@ type.
Semantics:
""""""""""
-Follows the IEEE754 2008 semantics for maxNum with +0.0>-0.0.
-This is more strict than current (C23) behavior of libm's fmax.
-Some applications like Clang, can call '``llvm.maxnum.*``' with '``nsz``' attribute
-to archive the same behaivor of libm's fmax.
+Follows the IEEE-754 semantics for minNum, except that -0.0 < +0.0 for the purposes
+of this intrinsic. As for signaling NaNs, per the IEEE-754 semantics, if either operand
+is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
+function fmin, although not all implementations have implemented these recommended behaviors.
-For some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, they have the
+If either operand is a qNaN, returns the other non-NaN operand. Returns
+NaN only if both operands are NaN or either operand is sNaN.
+
+If the operands compare equal, returns either one of the operands.
+
+Returns -0.0 for +0.0 vs -0.0. libm doesn't require it, so that
+some applications like Clang, can call '``llvm.minnum.*``' with '``nsz``' attribute
+to archive the required behaivors of libm's fmin.
+
+Some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have the
strictly same instructions; thus it is quite simple for these architectures.
For other architectures, the custom or expand methods may provide '``nsz``' flavor.
@@ -16798,10 +16812,6 @@ so arithmetic feeding into a maxnum can produce inconsistent results.
Such as `fmax(sNaN+0.0, 1.0)` can produce qNaN or 1.0 depending on whether `+0.0`
is optimized out.
-If either operand is a NaN, returns the other non-NaN operand. Returns
-NaN only if both operands are NaN or either operand is sNaN.
-If the operands compare equal, returns either one of the operands.
-
.. _i_minimum:
'``llvm.minimum.*``' Intrinsic
diff --git a/llvm/include/llvm/CodeGen/ISDOpcodes.h b/llvm/include/llvm/CodeGen/ISDOpcodes.h
index fd8784a4c10034..21de4d28ded0ed 100644
--- a/llvm/include/llvm/CodeGen/ISDOpcodes.h
+++ b/llvm/include/llvm/CodeGen/ISDOpcodes.h
@@ -1021,13 +1021,20 @@ enum NodeType {
LRINT,
LLRINT,
- /// FMINNUM/FMAXNUM - Perform floating-point minimum or maximum on two
- /// values.
+ /// FMINNUM/FMAXNUM - Perform floating-point minimum maximum on two values,
+ /// following IEEE-754 definitions.
///
- /// In the case where a single input is a NaN (either signaling or quiet),
- /// the non-NaN input is returned.
+ /// If one input is a signaling NaN, returns a quiet NaN. This matches
+ /// IEEE-754 2008's minnum/maxnum behavior for signaling NaNs (which differs
+ /// from 2019).
+ ///
+ /// These treat -0 as ordered less than +0, matching the behavior of IEEE-754
+ /// 2019's minimumNumber/maximumNumber.
///
- /// The return value of (FMINNUM 0.0, -0.0) could be either 0.0 or -0.0.
+ /// Note that that arithmetic on an sNaN doesn't consistently produce a qNaN,
+ /// so arithmetic feeding into a minnum/maxnum can produce inconsistent
+ /// results. FMAXIMUN/FMINIMUM or FMAXIMUMNUM/FMINIMUMNUM may be better choice
+ /// for non-distinction of sNaN/qNaN handling.
FMINNUM,
FMAXNUM,
>From 030dc3dc7386bebda2dc79f751b3975324ab15d9 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Fri, 1 Nov 2024 09:02:34 +0800
Subject: [PATCH 08/14] some improvement on wording
---
llvm/docs/LangRef.rst | 34 +++++++++++---------------
llvm/include/llvm/CodeGen/ISDOpcodes.h | 4 +--
2 files changed, 16 insertions(+), 22 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 77745601dd3618..0183867bb19358 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16731,15 +16731,12 @@ function fmin, although not all implementations have implemented these recommend
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
-If the operands compare equal, returns either one of the operands.
+This behavior is more strict than the definition in C and IEEE 754, where either zero may be returned.
+To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use the nsz
+attribute on the intrinsic call.
-Returns -0.0 for +0.0 vs -0.0. libm doesn't require it, so that
-some applications like Clang, can call '``llvm.minnum.*``' with '``nsz``' attribute
-to archive the required behaivors of libm's fmin.
-
-Some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have the
-strictly same instructions; thus it is quite simple for these architectures.
-For other architectures, the custom or expand methods may provide '``nsz``' flavor.
+Some architectures, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have instructions that match
+these semantics exactly; thus it is quite simple for these architectures.
Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
@@ -16793,15 +16790,12 @@ function fmin, although not all implementations have implemented these recommend
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or either operand is sNaN.
-If the operands compare equal, returns either one of the operands.
-
-Returns -0.0 for +0.0 vs -0.0. libm doesn't require it, so that
-some applications like Clang, can call '``llvm.minnum.*``' with '``nsz``' attribute
-to archive the required behaivors of libm's fmin.
+This behavior is more strict than the definition in C and IEEE 754, where either zero may be returned.
+To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use the nsz
+attribute on the intrinsic call.
-Some architecturs, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have the
-strictly same instructions; thus it is quite simple for these architectures.
-For other architectures, the custom or expand methods may provide '``nsz``' flavor.
+Some architectures, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have instructions that match
+these semantics exactly; thus it is quite simple for these architectures.
Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
@@ -19693,7 +19687,7 @@ intrinsic. If the intrinsic call has the ``nnan`` fast-math flag, then the
operation can assume that NaNs are not present in the input vector.
It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with Vector or SIMD extensions.
+outputs, and it is hard to optimize with vector or SIMD extensions.
Use '``llvm.vector.reduce.fmaximum``' or '``llvm.vector.reduce.fmaximumnum``' instead.
Arguments:
@@ -19726,7 +19720,7 @@ intrinsic. If the intrinsic call has the ``nnan`` fast-math flag, then the
operation can assume that NaNs are not present in the input vector.
It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with Vector or SIMD extensions.
+outputs, and it is hard to optimize with vector or SIMD extensions.
Use '``llvm.vector.reduce.fminimum``' or '``llvm.vector.reduce.fminimumnum``' instead.
Arguments:
@@ -23346,7 +23340,7 @@ This instruction has the same comparison semantics as the
To ignore the start value, the neutral value can be used.
It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with Vector or SIMD extensions.
+outputs, and it is hard to optimize with vector or SIMD extensions.
Use '``llvm.vp.vector.reduce.fmaximum``' or '``llvm.vp.vector.reduce.fmaximumnum``' instead.
Examples:
@@ -23417,7 +23411,7 @@ This instruction has the same comparison semantics as the
To ignore the start value, the neutral value can be used.
It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with Vector or SIMD extensions.
+outputs, and it is hard to optimize with vector or SIMD extensions.
Use '``llvm.vp.vector.reduce.fminimum``' or '``llvm.vp.vector.reduce.fminimumnum``' instead.
Examples:
diff --git a/llvm/include/llvm/CodeGen/ISDOpcodes.h b/llvm/include/llvm/CodeGen/ISDOpcodes.h
index 21de4d28ded0ed..8032e8202638af 100644
--- a/llvm/include/llvm/CodeGen/ISDOpcodes.h
+++ b/llvm/include/llvm/CodeGen/ISDOpcodes.h
@@ -1022,10 +1022,10 @@ enum NodeType {
LLRINT,
/// FMINNUM/FMAXNUM - Perform floating-point minimum maximum on two values,
- /// following IEEE-754 definitions.
+ /// following IEEE-754 definitions except for signed zero behavior.
///
/// If one input is a signaling NaN, returns a quiet NaN. This matches
- /// IEEE-754 2008's minnum/maxnum behavior for signaling NaNs (which differs
+ /// IEEE-754 2008's minNum/maxNum behavior for signaling NaNs (which differs
/// from 2019).
///
/// These treat -0 as ordered less than +0, matching the behavior of IEEE-754
>From 6747c43f6255703de3ce0cc19b8813f933cedd68 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Fri, 1 Nov 2024 09:27:03 +0800
Subject: [PATCH 09/14] libc may be different
---
llvm/docs/LangRef.rst | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 0183867bb19358..2de2ad0039a926 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16738,9 +16738,9 @@ attribute on the intrinsic call.
Some architectures, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have instructions that match
these semantics exactly; thus it is quite simple for these architectures.
-Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
-sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
-NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
+In the real libc worlds, the bebhaviors of fmin may be quite different on sNaN and signed zero behaviors,
+even in the same release of a single libm implemention. Such as in glibc 2.24, the Arm64 asm implemention
+has different behaviour with the generic C implemention.
Note that that arithmetic on an sNaN doesn't consistently produce a qNaN,
so arithmetic feeding into a minnum can produce inconsistent results.
@@ -16797,9 +16797,9 @@ attribute on the intrinsic call.
Some architectures, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have instructions that match
these semantics exactly; thus it is quite simple for these architectures.
-Historically, libc returns NUM for NUM vs (sNaN or qNaN), and may return
-sNaN for qNaN vs sNaN. With the recent libc versions, libc follows IEEE754-2008:
-NUM vs sNaN -> qNaN; NUM vs qNaN -> NUM; qNaN vs sNaN -> qNaN; sNaN vs sNaN -> qNaN.
+In the real libc worlds, the bebhaviors of fmin may be quite different on sNaN and signed zero behaviors,
+even in the same release of a single libm implemention. Such as in glibc 2.24, the Arm64 asm implemention
+has different behaviour with the generic C implemention.
Note that that arithmetic on an sNaN doesn't consistently produce a qNaN,
so arithmetic feeding into a maxnum can produce inconsistent results.
>From 4dcd6cfc143df20bbc1b5f846f36f1ff3ac79577 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Tue, 3 Dec 2024 09:34:42 +0800
Subject: [PATCH 10/14] Update
---
llvm/docs/LangRef.rst | 47 ++++++++++++++++----------
llvm/include/llvm/CodeGen/ISDOpcodes.h | 3 ++
2 files changed, 32 insertions(+), 18 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 2de2ad0039a926..0b0fc20a710f18 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16726,26 +16726,32 @@ Semantics:
Follows the IEEE-754 semantics for minNum, except that -0.0 < +0.0 for the purposes
of this intrinsic. As for signaling NaNs, per the IEEE-754 semantics, if either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
-function fmin, although not all implementations have implemented these recommended behaviors.
+function `fmin`, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns
-NaN only if both operands are NaN or either operand is sNaN.
+NaN only if both operands are NaN or if either operand is sNaN.
This behavior is more strict than the definition in C and IEEE 754, where either zero may be returned.
To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use the nsz
attribute on the intrinsic call.
-Some architectures, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have instructions that match
-these semantics exactly; thus it is quite simple for these architectures.
+If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
+and IEEE 754: the result of minnum(-0.0, +0.0) may be either -0.0 or +0.0.
+
+Some architectures, such as ARMv8 (FMINNM), LoongArch (fmin), MIPSr6 (min.fmt), PowerPC/VSX (xsmindp),
+have instructions that match these semantics exactly; thus it is quite simple for these architectures.
+Some architectures have similiar while they are not exact equivalent. Such as x86 implements `MINPS`,
+which implements the semantics of C code `a<b?a:b`: NUM vs qNaN always return qNaN. `MINPS` can be used
+if `nsz` and `nnan` are given.
+
In the real libc worlds, the bebhaviors of fmin may be quite different on sNaN and signed zero behaviors,
-even in the same release of a single libm implemention. Such as in glibc 2.24, the Arm64 asm implemention
-has different behaviour with the generic C implemention.
+even in the same release of a single libm implemention.
-Note that that arithmetic on an sNaN doesn't consistently produce a qNaN,
+Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
so arithmetic feeding into a minnum can produce inconsistent results.
-Such as `fmin(sNaN+0.0, 1.0)` can produce qNaN or 1.0 depending on whether `+0.0`
-is optimized out.
+For example, `maxnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd`
+is folded.
.. _i_maxnum:
@@ -16785,26 +16791,31 @@ Semantics:
Follows the IEEE-754 semantics for minNum, except that -0.0 < +0.0 for the purposes
of this intrinsic. As for signaling NaNs, per the IEEE-754 semantics, if either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
-function fmin, although not all implementations have implemented these recommended behaviors.
+function `fmax`, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns
-NaN only if both operands are NaN or either operand is sNaN.
+NaN only if both operands are NaN or if either operand is sNaN.
This behavior is more strict than the definition in C and IEEE 754, where either zero may be returned.
To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use the nsz
attribute on the intrinsic call.
-Some architectures, such as ARMv8, LoongArch, MIPSr6, PowerPC/VSX, have instructions that match
-these semantics exactly; thus it is quite simple for these architectures.
+If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
+and IEEE 754: the result of maxnum(-0.0, +0.0) may be either -0.0 or +0.0.
+
+Some architectures, such as ARMv8 (FMAXNM), LoongArch (fmax), MIPSr6 (max.fmt), PowerPC/VSX (xsmaxdp),
+have instructions that match these semantics exactly; thus it is quite simple for these architectures.
+Some architectures have similiar while they are not exact equivalent. Such as x86 implements `MAXPS`,
+which implements the semantics of C code `a>b?a:b`: NUM vs qNaN always return qNaN. `MAXPS` can be used
+if `nsz` and `nnan` are given.
In the real libc worlds, the bebhaviors of fmin may be quite different on sNaN and signed zero behaviors,
-even in the same release of a single libm implemention. Such as in glibc 2.24, the Arm64 asm implemention
-has different behaviour with the generic C implemention.
+even in the same release of a single libm implemention.
-Note that that arithmetic on an sNaN doesn't consistently produce a qNaN,
+Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
so arithmetic feeding into a maxnum can produce inconsistent results.
-Such as `fmax(sNaN+0.0, 1.0)` can produce qNaN or 1.0 depending on whether `+0.0`
-is optimized out.
+For example, `maxnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd`
+is folded.
.. _i_minimum:
diff --git a/llvm/include/llvm/CodeGen/ISDOpcodes.h b/llvm/include/llvm/CodeGen/ISDOpcodes.h
index 8032e8202638af..678ed8c8a6fa3a 100644
--- a/llvm/include/llvm/CodeGen/ISDOpcodes.h
+++ b/llvm/include/llvm/CodeGen/ISDOpcodes.h
@@ -1048,6 +1048,9 @@ enum NodeType {
///
/// These treat -0 as ordered less than +0, matching the behavior of IEEE-754
/// 2019's minimumNumber/maximumNumber.
+ ///
+ /// Deprecated, and will be removed soon, as FMINNUM/FMAXNUM have the same
+ /// semantics now.
FMINNUM_IEEE,
FMAXNUM_IEEE,
>From 0db53788e2097688fc29805cea410d5a0c8c8ea5 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Wed, 4 Dec 2024 10:33:47 +0800
Subject: [PATCH 11/14] highlight IEEE-754-2008
---
llvm/docs/LangRef.rst | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 0b0fc20a710f18..cf939381e38ba8 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16723,20 +16723,20 @@ type.
Semantics:
""""""""""
-Follows the IEEE-754 semantics for minNum, except that -0.0 < +0.0 for the purposes
-of this intrinsic. As for signaling NaNs, per the IEEE-754 semantics, if either operand
+Follows the semantics of minNum in IEEE-754-2008, except that -0.0 < +0.0 for the purposes
+of this intrinsic. As for signaling NaNs, per the minNum semantics, if either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
function `fmin`, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or if either operand is sNaN.
-This behavior is more strict than the definition in C and IEEE 754, where either zero may be returned.
-To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use the nsz
-attribute on the intrinsic call.
+This behavior is stricter than minNum in IEEE-754-2008, where either zero may be returned.
+To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use
+the nsz attribute.
If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
-and IEEE 754: the result of minnum(-0.0, +0.0) may be either -0.0 or +0.0.
+and IEEE-754-2008: the result of minnum(-0.0, +0.0) may be either -0.0 or +0.0.
Some architectures, such as ARMv8 (FMINNM), LoongArch (fmin), MIPSr6 (min.fmt), PowerPC/VSX (xsmindp),
have instructions that match these semantics exactly; thus it is quite simple for these architectures.
@@ -16788,20 +16788,20 @@ type.
Semantics:
""""""""""
-Follows the IEEE-754 semantics for minNum, except that -0.0 < +0.0 for the purposes
-of this intrinsic. As for signaling NaNs, per the IEEE-754 semantics, if either operand
+Follows the semantics of maxNum in IEEE-754-2008, except that -0.0 < +0.0 for the purposes
+of this intrinsic. As for signaling NaNs, per the maxNum semantics, if either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
function `fmax`, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or if either operand is sNaN.
-This behavior is more strict than the definition in C and IEEE 754, where either zero may be returned.
-To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use the nsz
-attribute on the intrinsic call.
+This behavior is stricter than maxNum in IEEE-754-2008, where either zero may be returned.
+To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use
+the nsz attribute.
If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
-and IEEE 754: the result of maxnum(-0.0, +0.0) may be either -0.0 or +0.0.
+and IEEE-754-2008: the result of maxnum(-0.0, +0.0) may be either -0.0 or +0.0.
Some architectures, such as ARMv8 (FMAXNM), LoongArch (fmax), MIPSr6 (max.fmt), PowerPC/VSX (xsmaxdp),
have instructions that match these semantics exactly; thus it is quite simple for these architectures.
@@ -21998,7 +21998,7 @@ This is an overloaded intrinsic.
Overview:
"""""""""
-Predicated floating-point IEEE-754 minNum of two vectors of floating-point values.
+Predicated floating-point IEEE-754-2008 minNum of two vectors of floating-point values.
Arguments:
@@ -22047,7 +22047,7 @@ This is an overloaded intrinsic.
Overview:
"""""""""
-Predicated floating-point IEEE-754 maxNum of two vectors of floating-point values.
+Predicated floating-point IEEE-754-2008 maxNum of two vectors of floating-point values.
Arguments:
@@ -28091,7 +28091,7 @@ The third argument specifies the exception behavior as described above.
Semantics:
""""""""""
-This function follows the IEEE-754 semantics for maxNum.
+This function follows the IEEE-754-2008 semantics for maxNum.
'``llvm.experimental.constrained.minnum``' Intrinsic
@@ -28123,7 +28123,7 @@ The third argument specifies the exception behavior as described above.
Semantics:
""""""""""
-This function follows the IEEE-754 semantics for minNum.
+This function follows the IEEE-754-2008 semantics for minNum.
'``llvm.experimental.constrained.maximum``' Intrinsic
>From ad8b9dbdbd183d2da28d84cacc83be115967f7d3 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Thu, 5 Dec 2024 09:52:02 +0800
Subject: [PATCH 12/14] define with 2019; remove deprecated about vector*
---
llvm/docs/LangRef.rst | 40 +++++++++++-----------------------------
1 file changed, 11 insertions(+), 29 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index cf939381e38ba8..ff1d0ef6698ee7 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16723,24 +16723,23 @@ type.
Semantics:
""""""""""
-Follows the semantics of minNum in IEEE-754-2008, except that -0.0 < +0.0 for the purposes
-of this intrinsic. As for signaling NaNs, per the minNum semantics, if either operand
+Follows the semantics of mininumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
function `fmin`, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or if either operand is sNaN.
-This behavior is stricter than minNum in IEEE-754-2008, where either zero may be returned.
-To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use
-the nsz attribute.
+IEEE-754-2008 defines minNum, and it is removed in IEEE-754-2019. The behavior of this intrinsic is
+stricter than minNum in IEEE-754-2008, where either zero may be returned. To achieve the same permissiveness,
+the backend may implement the nsz attribute, and one may use the nsz attribute.
If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
and IEEE-754-2008: the result of minnum(-0.0, +0.0) may be either -0.0 or +0.0.
Some architectures, such as ARMv8 (FMINNM), LoongArch (fmin), MIPSr6 (min.fmt), PowerPC/VSX (xsmindp),
have instructions that match these semantics exactly; thus it is quite simple for these architectures.
-Some architectures have similiar while they are not exact equivalent. Such as x86 implements `MINPS`,
+Some architectures have similiar ones while they are not exact equivalent. Such as x86 implements `MINPS`,
which implements the semantics of C code `a<b?a:b`: NUM vs qNaN always return qNaN. `MINPS` can be used
if `nsz` and `nnan` are given.
@@ -16788,24 +16787,23 @@ type.
Semantics:
""""""""""
-Follows the semantics of maxNum in IEEE-754-2008, except that -0.0 < +0.0 for the purposes
-of this intrinsic. As for signaling NaNs, per the maxNum semantics, if either operand
+Follows the semantics of maxinumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
-function `fmax`, although not all implementations have implemented these recommended behaviors.
+function `fmin`, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns
NaN only if both operands are NaN or if either operand is sNaN.
-This behavior is stricter than maxNum in IEEE-754-2008, where either zero may be returned.
-To achieve the same permissiveness, the backend may implement the nsz attribute, and one may use
-the nsz attribute.
+IEEE-754-2008 defines maxNum, and it is removed in IEEE-754-2019. The behavior of this intrinsic is
+stricter than minNum in IEEE-754-2008, where either zero may be returned. To achieve the same permissiveness,
+the backend may implement the nsz attribute, and one may use the nsz attribute.
If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
and IEEE-754-2008: the result of maxnum(-0.0, +0.0) may be either -0.0 or +0.0.
Some architectures, such as ARMv8 (FMAXNM), LoongArch (fmax), MIPSr6 (max.fmt), PowerPC/VSX (xsmaxdp),
have instructions that match these semantics exactly; thus it is quite simple for these architectures.
-Some architectures have similiar while they are not exact equivalent. Such as x86 implements `MAXPS`,
+Some architectures have similiar ones while they are not exact equivalent. Such as x86 implements `MAXPS`,
which implements the semantics of C code `a>b?a:b`: NUM vs qNaN always return qNaN. `MAXPS` can be used
if `nsz` and `nnan` are given.
@@ -19697,10 +19695,6 @@ This instruction has the same comparison semantics as the '``llvm.maxnum.*``'
intrinsic. If the intrinsic call has the ``nnan`` fast-math flag, then the
operation can assume that NaNs are not present in the input vector.
-It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with vector or SIMD extensions.
-Use '``llvm.vector.reduce.fmaximum``' or '``llvm.vector.reduce.fmaximumnum``' instead.
-
Arguments:
""""""""""
The argument to this intrinsic must be a vector of floating-point values.
@@ -19730,10 +19724,6 @@ This instruction has the same comparison semantics as the '``llvm.minnum.*``'
intrinsic. If the intrinsic call has the ``nnan`` fast-math flag, then the
operation can assume that NaNs are not present in the input vector.
-It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with vector or SIMD extensions.
-Use '``llvm.vector.reduce.fminimum``' or '``llvm.vector.reduce.fminimumnum``' instead.
-
Arguments:
""""""""""
The argument to this intrinsic must be a vector of floating-point values.
@@ -23350,10 +23340,6 @@ This instruction has the same comparison semantics as the
To ignore the start value, the neutral value can be used.
-It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with vector or SIMD extensions.
-Use '``llvm.vp.vector.reduce.fmaximum``' or '``llvm.vp.vector.reduce.fmaximumnum``' instead.
-
Examples:
"""""""""
@@ -23421,10 +23407,6 @@ This instruction has the same comparison semantics as the
To ignore the start value, the neutral value can be used.
-It is deprecated, since the different order of inputs may produce different
-outputs, and it is hard to optimize with vector or SIMD extensions.
-Use '``llvm.vp.vector.reduce.fminimum``' or '``llvm.vp.vector.reduce.fminimumnum``' instead.
-
Examples:
"""""""""
>From a655204d8c443302478d1c61dd0fd7e3f5acf486 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Mon, 9 Dec 2024 10:05:36 +0800
Subject: [PATCH 13/14] fix typo minimum
---
llvm/docs/LangRef.rst | 27 ++++++++++-----------------
1 file changed, 10 insertions(+), 17 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index ff1d0ef6698ee7..f207426f61992a 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16723,12 +16723,14 @@ type.
Semantics:
""""""""""
-Follows the semantics of mininumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
+Follows the semantics of minimumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
function `fmin`, although not all implementations have implemented these recommended behaviors.
-If either operand is a qNaN, returns the other non-NaN operand. Returns
-NaN only if both operands are NaN or if either operand is sNaN.
+If either operand is a qNaN, returns the other non-NaN operand. Returns NaN only if both operands are
+NaN or if either operand is sNaN. Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
+so arithmetic feeding into a minnum can produce inconsistent results. For example,
+`minnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd` is folded.
IEEE-754-2008 defines minNum, and it is removed in IEEE-754-2019. The behavior of this intrinsic is
stricter than minNum in IEEE-754-2008, where either zero may be returned. To achieve the same permissiveness,
@@ -16743,15 +16745,9 @@ Some architectures have similiar ones while they are not exact equivalent. Such
which implements the semantics of C code `a<b?a:b`: NUM vs qNaN always return qNaN. `MINPS` can be used
if `nsz` and `nnan` are given.
-
In the real libc worlds, the bebhaviors of fmin may be quite different on sNaN and signed zero behaviors,
even in the same release of a single libm implemention.
-Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
-so arithmetic feeding into a minnum can produce inconsistent results.
-For example, `maxnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd`
-is folded.
-
.. _i_maxnum:
'``llvm.maxnum.*``' Intrinsic
@@ -16787,12 +16783,14 @@ type.
Semantics:
""""""""""
-Follows the semantics of maxinumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
+Follows the semantics of maximumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
function `fmin`, although not all implementations have implemented these recommended behaviors.
-If either operand is a qNaN, returns the other non-NaN operand. Returns
-NaN only if both operands are NaN or if either operand is sNaN.
+If either operand is a qNaN, returns the other non-NaN operand. Returns NaN only if both operands are
+NaN or if either operand is sNaN. Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
+so arithmetic feeding into a maxnum can produce inconsistent results. For example,
+`maxnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd` is folded.
IEEE-754-2008 defines maxNum, and it is removed in IEEE-754-2019. The behavior of this intrinsic is
stricter than minNum in IEEE-754-2008, where either zero may be returned. To achieve the same permissiveness,
@@ -16810,11 +16808,6 @@ if `nsz` and `nnan` are given.
In the real libc worlds, the bebhaviors of fmin may be quite different on sNaN and signed zero behaviors,
even in the same release of a single libm implemention.
-Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
-so arithmetic feeding into a maxnum can produce inconsistent results.
-For example, `maxnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd`
-is folded.
-
.. _i_minimum:
'``llvm.minimum.*``' Intrinsic
>From 02af55163ea2162a40308e44a0fd2dd6050bbca6 Mon Sep 17 00:00:00 2001
From: YunQiang Su <yunqiang at isrc.iscas.ac.cn>
Date: Wed, 22 Jan 2025 09:46:28 +0800
Subject: [PATCH 14/14] some fix
---
llvm/docs/LangRef.rst | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index f207426f61992a..b87e0fe15fdcc9 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -16725,7 +16725,7 @@ Semantics:
""""""""""
Follows the semantics of minimumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
-function `fmin`, although not all implementations have implemented these recommended behaviors.
+function ``fmin``, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns NaN only if both operands are
NaN or if either operand is sNaN. Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
@@ -16733,8 +16733,7 @@ so arithmetic feeding into a minnum can produce inconsistent results. For exampl
`minnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd` is folded.
IEEE-754-2008 defines minNum, and it is removed in IEEE-754-2019. The behavior of this intrinsic is
-stricter than minNum in IEEE-754-2008, where either zero may be returned. To achieve the same permissiveness,
-the backend may implement the nsz attribute, and one may use the nsz attribute.
+stricter than minNum in IEEE-754-2008, where either zero may be returned.
If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
and IEEE-754-2008: the result of minnum(-0.0, +0.0) may be either -0.0 or +0.0.
@@ -16785,7 +16784,7 @@ Semantics:
""""""""""
Follows the semantics of maximumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
-function `fmin`, although not all implementations have implemented these recommended behaviors.
+function ``fmax``, although not all implementations have implemented these recommended behaviors.
If either operand is a qNaN, returns the other non-NaN operand. Returns NaN only if both operands are
NaN or if either operand is sNaN. Note that arithmetic on an sNaN doesn't consistently produce a qNaN,
@@ -16793,8 +16792,7 @@ so arithmetic feeding into a maxnum can produce inconsistent results. For exampl
`maxnum(fadd(sNaN, 0.0), 1.0)` can produce qNaN or 1.0 depending on whether `fadd` is folded.
IEEE-754-2008 defines maxNum, and it is removed in IEEE-754-2019. The behavior of this intrinsic is
-stricter than minNum in IEEE-754-2008, where either zero may be returned. To achieve the same permissiveness,
-the backend may implement the nsz attribute, and one may use the nsz attribute.
+stricter than minNum in IEEE-754-2008, where either zero may be returned.
If the intrinsic is marked with the nsz attribute, then the effect is as in the definition in C
and IEEE-754-2008: the result of maxnum(-0.0, +0.0) may be either -0.0 or +0.0.
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