sync_up: Discussion page for tomorrow's meeting

[libreriscv.git] / ztrans_proposal.mdwn

diff --git a/ztrans_proposal.mdwn b/ztrans_proposal.mdwn
index 7610755be5fe9d92f648716350f6cc726cf0a1d1..ca73c4220a0faf66a30917a4b688fe32d0a6a657 100644 (file)
--- a/ztrans_proposal.mdwn
+++ b/ztrans_proposal.mdwn
@@ -1,7 +1,14 @@
+**OBSOLETE**, superceded by [[openpower/transcendentals]]
+

 # Zftrans - transcendental operations
 
 # Zftrans - transcendental operations
 

-With thanks to:
+Summary:
+
+*This proposal extends RISC-V scalar floating point operations to add IEEE754 transcendental functions (pow, log etc) and trigonometric functions (sin, cos etc). These functions are also 98% shared with the Khronos Group OpenCL Extended Instruction Set.*

 
 

+Authors/Contributors:
+
+* Luke Kenneth Casson Leighton

 * Jacob Lifshay
 * Dan Petroski
 * Mitch Alsup
 * Jacob Lifshay
 * Dan Petroski
 * Mitch Alsup


@@ -54,7 +61,7 @@ Minimum recommended requirements for Mobile-Embedded 3D: Ztrignpi, Zftrans, with
 
 This proposal is designed to meet a wide range of extremely diverse needs,
 allowing implementors from all of them to benefit from the tools and hardware
 
 This proposal is designed to meet a wide range of extremely diverse needs,
 allowing implementors from all of them to benefit from the tools and hardware

-cost reductions associated with common standards adoption.
+cost reductions associated with common standards adoption in RISC-V (primarily IEEE754 and Vulkan).

 
 **There are *four* different, disparate platform's needs (two new)**:
 
 
 **There are *four* different, disparate platform's needs (two new)**:
 


@@ -210,11 +217,14 @@ Any deviation from Trademarked Standards means that an implementation
 may not be sold and also make a claim of being, for example, "Vulkan
 compatible".
 
 may not be sold and also make a claim of being, for example, "Vulkan
 compatible".
 

-This in turn reinforces and makes a hard requirement a need for public
+For 3D, this in turn reinforces and makes a hard requirement a need for public

 compliance with such standards, over-and-above what would otherwise be
 set by a RISC-V Standards Development Process, including both the
 software compliance and the knock-on implications that has for hardware.
 
 compliance with such standards, over-and-above what would otherwise be
 set by a RISC-V Standards Development Process, including both the
 software compliance and the knock-on implications that has for hardware.
 

+For libraries such as libm and numpy, accuracy is paramount, for software  interoperability across multiple platforms. Some algorithms critically rely on correct IEEE754, for example.
+The conflicting accuracy requirements can be met through the zfpacc extension.
+

 **Collaboration**:
 
 The case for collaboration on any Extension is already well-known.
 **Collaboration**:
 
 The case for collaboration on any Extension is already well-known.


@@ -312,8 +322,11 @@ numbers of potential opcodes.  BitManip is the perfect counter-example.
 
 # Proposed Opcodes vs Khronos OpenCL vs IEEE754-2019<a name="khronos_equiv"></a>
 
 
 # Proposed Opcodes vs Khronos OpenCL vs IEEE754-2019<a name="khronos_equiv"></a>
 

-This list shows the (direct) equivalence between proposed opcodes and
-their Khronos OpenCL equivalents.
+This list shows the (direct) equivalence between proposed opcodes,
+their Khronos OpenCL equivalents, and their IEEE754-2019 equivalents.
+98% of the opcodes in this proposal that are in the IEEE754-2019 standard
+are present in the Khronos Extended Instruction Set.
+

 For RISCV opcode encodings see 
 [[rv_major_opcode_1010011]]
 
 For RISCV opcode encodings see 
 [[rv_major_opcode_1010011]]
 


@@ -363,7 +376,7 @@ FATANH   | atanh       | NONE        | NONE          | NONE        | atanh    |
 FATAN2   | atan2       | NONE        | NONE          | NONE        | atan2    |
 FATAN2PI | atan2pi     | NONE        | NONE          | NONE        | atan2pi  |
 FRSQRT   | rsqrt       | half\_rsqrt | native\_rsqrt | NONE        | rSqrt    |
 FATAN2   | atan2       | NONE        | NONE          | NONE        | atan2    |
 FATAN2PI | atan2pi     | NONE        | NONE          | NONE        | atan2pi  |
 FRSQRT   | rsqrt       | half\_rsqrt | native\_rsqrt | NONE        | rSqrt    |

-FCBRT    | cbrt        | NONE        | NONE          | NONE        | NONE (4) |
+FCBRT    | cbrt        | NONE        | NONE          | NONE        | NONE (2) |

 FEXP2    | exp2        | half\_exp2  | native\_exp2  | NONE        | exp2     |
 FLOG2    | log2        | half\_log2  | native\_log2  | NONE        | log2     |
 FEXPM1   | expm1       | NONE        | NONE          | NONE        | expm1    |
 FEXP2    | exp2        | half\_exp2  | native\_exp2  | NONE        | exp2     |
 FLOG2    | log2        | half\_log2  | native\_log2  | NONE        | log2     |
 FEXPM1   | expm1       | NONE        | NONE          | NONE        | expm1    |


@@ -373,27 +386,23 @@ FLOG     | log         | half\_log   | native\_log   | NONE        | log      |
 FEXP10   | exp10       | half\_exp10 | native\_exp10 | NONE        | exp10    |
 FLOG10   | log10       | half\_log10 | native\_log10 | NONE        | log10    |
 FPOW     | pow         | NONE        | NONE          | NONE        | pow      |
 FEXP10   | exp10       | half\_exp10 | native\_exp10 | NONE        | exp10    |
 FLOG10   | log10       | half\_log10 | native\_log10 | NONE        | log10    |
 FPOW     | pow         | NONE        | NONE          | NONE        | pow      |

+FPOWN    | pown        | NONE        | NONE          | NONE        | pown     |
+FPOWR    | powr        | half\_powr  | native\_powr  | NONE        | powr     |

 FROOTN   | rootn       | NONE        | NONE          | NONE        | rootn    |
 FHYPOT   | hypot       | NONE        | NONE          | NONE        | hypot    |
 FROOTN   | rootn       | NONE        | NONE          | NONE        | rootn    |
 FHYPOT   | hypot       | NONE        | NONE          | NONE        | hypot    |

-FRECIP   | NONE        | half\_recip | native\_recip | NONE        | NONE (5) |
+FRECIP   | NONE        | half\_recip | native\_recip | NONE        | NONE (3) |

 NONE     | NONE        | NONE        | NONE          | NONE        | compound |
 NONE     | NONE        | NONE        | NONE          | NONE        | exp2m1   |
 NONE     | NONE        | NONE        | NONE          | NONE        | exp10m1  |
 NONE     | NONE        | NONE        | NONE          | NONE        | log2p1   |
 NONE     | NONE        | NONE        | NONE          | NONE        | log10p1  |
 NONE     | NONE        | NONE        | NONE          | NONE        | compound |
 NONE     | NONE        | NONE        | NONE          | NONE        | exp2m1   |
 NONE     | NONE        | NONE        | NONE          | NONE        | exp10m1  |
 NONE     | NONE        | NONE        | NONE          | NONE        | log2p1   |
 NONE     | NONE        | NONE        | NONE          | NONE        | log10p1  |

-NONE     | NONE        | NONE        | NONE          | NONE        | pown (2) |
-NONE     | NONE        | NONE        | NONE          | NONE        | powr (3) |

 """]]
 
 Note (1) FSINCOS is macro-op fused (see below).
 
 """]]
 
 Note (1) FSINCOS is macro-op fused (see below).
 

-Note (2) IEEE754-2019 pown(x, n) - n is an integer
-
-Note (3) IEEE754-2019 powr(x, y) is defined as "exp(y log (x))"
+Note (2) synthesised in IEEE754-2019 as "pown(x, 3)"

 
 

-Note (4) synthesised in IEEE754-2019 as "pown(x, 3)"
-
-Note (5) synthesised in IEEE754-2019 using "1.0 / x"
+Note (3) synthesised in IEEE754-2019 using "1.0 / x"

 
 ## List of 2-arg opcodes
 
 
 ## List of 2-arg opcodes
 


@@ -402,6 +411,8 @@ opcode    | Description            | pseudocode                 | Extension   |
 FATAN2    | atan2 arc tangent      | rd = atan2(rs2, rs1)       | Zarctrignpi |
 FATAN2PI  | atan2 arc tangent / pi | rd = atan2(rs2, rs1) / pi  | Zarctrigpi  |
 FPOW      | x power of y           | rd = pow(rs1, rs2)         | ZftransAdv  |
 FATAN2    | atan2 arc tangent      | rd = atan2(rs2, rs1)       | Zarctrignpi |
 FATAN2PI  | atan2 arc tangent / pi | rd = atan2(rs2, rs1) / pi  | Zarctrigpi  |
 FPOW      | x power of y           | rd = pow(rs1, rs2)         | ZftransAdv  |

+FPOWN     | x power of n (n int)   | rd = pow(rs1, rs2)         | ZftransAdv  |
+FPOWR     | x power of y (x +ve)   | rd = exp(rs1 log(rs2))     | ZftransAdv  |

 FROOTN    | x power 1/n (n integer)| rd = pow(rs1, 1/rs2)       | ZftransAdv  |
 FHYPOT    | hypotenuse             | rd = sqrt(rs1^2 + rs2^2)   | ZftransAdv  |
 """]]
 FROOTN    | x power 1/n (n integer)| rd = pow(rs1, 1/rs2)       | ZftransAdv  |
 FHYPOT    | hypotenuse             | rd = sqrt(rs1^2 + rs2^2)   | ZftransAdv  |
 """]]


@@ -435,7 +446,6 @@ FACOS       | arccos (radians)         | rd = acos(rs1)          | Zarctrignpi |
 FATAN       | arctan (radians)         | rd = atan(rs1)          | Zarctrignpi |
 FSINPI      | sin times pi             | rd = sin(pi * rs1)      | Ztrigpi |
 FCOSPI      | cos times pi             | rd = cos(pi * rs1)      | Ztrigpi |
 FATAN       | arctan (radians)         | rd = atan(rs1)          | Zarctrignpi |
 FSINPI      | sin times pi             | rd = sin(pi * rs1)      | Ztrigpi |
 FCOSPI      | cos times pi             | rd = cos(pi * rs1)      | Ztrigpi |

-

 FTANPI      | tan times pi             | rd = tan(pi * rs1)      | Ztrigpi |
 FASINPI     | arcsin / pi              | rd = asin(rs1) / pi     | Zarctrigpi |
 FACOSPI     | arccos / pi              | rd = acos(rs1) / pi     | Zarctrigpi |
 FTANPI      | tan times pi             | rd = tan(pi * rs1)      | Ztrigpi |
 FASINPI     | arcsin / pi              | rd = asin(rs1) / pi     | Zarctrigpi |
 FACOSPI     | arccos / pi              | rd = acos(rs1) / pi     | Zarctrigpi |


@@ -556,7 +566,7 @@ HPC and high-end GPUs are likely markets for these.
 
 ### ZftransAdv
 
 
 ### ZftransAdv
 

-CBRT, POW, ROOTN
+CBRT, POW, POWN, POWR, ROOTN

 
 These are simply much more complex to implement in hardware, and typically
 will only be put into HPC applications.
 
 These are simply much more complex to implement in hardware, and typically
 will only be put into HPC applications.