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Diffstat (limited to 'Documentation/arm/nwfpe')
| -rw-r--r-- | Documentation/arm/nwfpe/index.rst | 13 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/netwinder-fpe.rst | 162 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/notes.rst | 32 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/nwfpe.rst | 74 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/todo.rst | 72 |
5 files changed, 0 insertions, 353 deletions
diff --git a/Documentation/arm/nwfpe/index.rst b/Documentation/arm/nwfpe/index.rst deleted file mode 100644 index 3c4d2f9aa10e..000000000000 --- a/Documentation/arm/nwfpe/index.rst +++ /dev/null @@ -1,13 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -=================================== -NetWinder's floating point emulator -=================================== - -.. toctree:: - :maxdepth: 1 - - nwfpe - netwinder-fpe - notes - todo diff --git a/Documentation/arm/nwfpe/netwinder-fpe.rst b/Documentation/arm/nwfpe/netwinder-fpe.rst deleted file mode 100644 index cbb320960fc4..000000000000 --- a/Documentation/arm/nwfpe/netwinder-fpe.rst +++ /dev/null @@ -1,162 +0,0 @@ -============= -Current State -============= - -The following describes the current state of the NetWinder's floating point -emulator. - -In the following nomenclature is used to describe the floating point -instructions. It follows the conventions in the ARM manual. - -:: - - <S|D|E> = <single|double|extended>, no default - {P|M|Z} = {round to +infinity,round to -infinity,round to zero}, - default = round to nearest - -Note: items enclosed in {} are optional. - -Floating Point Coprocessor Data Transfer Instructions (CPDT) ------------------------------------------------------------- - -LDF/STF - load and store floating - -<LDF|STF>{cond}<S|D|E> Fd, Rn -<LDF|STF>{cond}<S|D|E> Fd, [Rn, #<expression>]{!} -<LDF|STF>{cond}<S|D|E> Fd, [Rn], #<expression> - -These instructions are fully implemented. - -LFM/SFM - load and store multiple floating - -Form 1 syntax: -<LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn] -<LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn, #<expression>]{!} -<LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn], #<expression> - -Form 2 syntax: -<LFM|SFM>{cond}<FD,EA> Fd, <count>, [Rn]{!} - -These instructions are fully implemented. They store/load three words -for each floating point register into the memory location given in the -instruction. The format in memory is unlikely to be compatible with -other implementations, in particular the actual hardware. Specific -mention of this is made in the ARM manuals. - -Floating Point Coprocessor Register Transfer Instructions (CPRT) ----------------------------------------------------------------- - -Conversions, read/write status/control register instructions - -FLT{cond}<S,D,E>{P,M,Z} Fn, Rd Convert integer to floating point -FIX{cond}{P,M,Z} Rd, Fn Convert floating point to integer -WFS{cond} Rd Write floating point status register -RFS{cond} Rd Read floating point status register -WFC{cond} Rd Write floating point control register -RFC{cond} Rd Read floating point control register - -FLT/FIX are fully implemented. - -RFS/WFS are fully implemented. - -RFC/WFC are fully implemented. RFC/WFC are supervisor only instructions, and -presently check the CPU mode, and do an invalid instruction trap if not called -from supervisor mode. - -Compare instructions - -CMF{cond} Fn, Fm Compare floating -CMFE{cond} Fn, Fm Compare floating with exception -CNF{cond} Fn, Fm Compare negated floating -CNFE{cond} Fn, Fm Compare negated floating with exception - -These are fully implemented. - -Floating Point Coprocessor Data Instructions (CPDT) ---------------------------------------------------- - -Dyadic operations: - -ADF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - add -SUF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - subtract -RSF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse subtract -MUF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - multiply -DVF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - divide -RDV{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse divide - -These are fully implemented. - -FML{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast multiply -FDV{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast divide -FRD{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast reverse divide - -These are fully implemented as well. They use the same algorithm as the -non-fast versions. Hence, in this implementation their performance is -equivalent to the MUF/DVF/RDV instructions. This is acceptable according -to the ARM manual. The manual notes these are defined only for single -operands, on the actual FPA11 hardware they do not work for double or -extended precision operands. The emulator currently does not check -the requested permissions conditions, and performs the requested operation. - -RMF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - IEEE remainder - -This is fully implemented. - -Monadic operations: - -MVF{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - move -MNF{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - move negated - -These are fully implemented. - -ABS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - absolute value -SQT{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - square root -RND{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - round - -These are fully implemented. - -URD{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - unnormalized round -NRM{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - normalize - -These are implemented. URD is implemented using the same code as the RND -instruction. Since URD cannot return a unnormalized number, NRM becomes -a NOP. - -Library calls: - -POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power -RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power -POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2) - -LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10 -LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e -EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent -SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine -COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine -TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent -ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine -ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine -ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent - -These are not implemented. They are not currently issued by the compiler, -and are handled by routines in libc. These are not implemented by the FPA11 -hardware, but are handled by the floating point support code. They should -be implemented in future versions. - -Signalling: - -Signals are implemented. However current ELF kernels produced by Rebel.com -have a bug in them that prevents the module from generating a SIGFPE. This -is caused by a failure to alias fp_current to the kernel variable -current_set[0] correctly. - -The kernel provided with this distribution (vmlinux-nwfpe-0.93) contains -a fix for this problem and also incorporates the current version of the -emulator directly. It is possible to run with no floating point module -loaded with this kernel. It is provided as a demonstration of the -technology and for those who want to do floating point work that depends -on signals. It is not strictly necessary to use the module. - -A module (either the one provided by Russell King, or the one in this -distribution) can be loaded to replace the functionality of the emulator -built into the kernel. diff --git a/Documentation/arm/nwfpe/notes.rst b/Documentation/arm/nwfpe/notes.rst deleted file mode 100644 index 102e55af8439..000000000000 --- a/Documentation/arm/nwfpe/notes.rst +++ /dev/null @@ -1,32 +0,0 @@ -Notes -===== - -There seems to be a problem with exp(double) and our emulator. I haven't -been able to track it down yet. This does not occur with the emulator -supplied by Russell King. - -I also found one oddity in the emulator. I don't think it is serious but -will point it out. The ARM calling conventions require floating point -registers f4-f7 to be preserved over a function call. The compiler quite -often uses an stfe instruction to save f4 on the stack upon entry to a -function, and an ldfe instruction to restore it before returning. - -I was looking at some code, that calculated a double result, stored it in f4 -then made a function call. Upon return from the function call the number in -f4 had been converted to an extended value in the emulator. - -This is a side effect of the stfe instruction. The double in f4 had to be -converted to extended, then stored. If an lfm/sfm combination had been used, -then no conversion would occur. This has performance considerations. The -result from the function call and f4 were used in a multiplication. If the -emulator sees a multiply of a double and extended, it promotes the double to -extended, then does the multiply in extended precision. - -This code will cause this problem: - -double x, y, z; -z = log(x)/log(y); - -The result of log(x) (a double) will be calculated, returned in f0, then -moved to f4 to preserve it over the log(y) call. The division will be done -in extended precision, due to the stfe instruction used to save f4 in log(y). diff --git a/Documentation/arm/nwfpe/nwfpe.rst b/Documentation/arm/nwfpe/nwfpe.rst deleted file mode 100644 index 35cd90dacbff..000000000000 --- a/Documentation/arm/nwfpe/nwfpe.rst +++ /dev/null @@ -1,74 +0,0 @@ -Introduction -============ - -This directory contains the version 0.92 test release of the NetWinder -Floating Point Emulator. - -The majority of the code was written by me, Scott Bambrough It is -written in C, with a small number of routines in inline assembler -where required. It was written quickly, with a goal of implementing a -working version of all the floating point instructions the compiler -emits as the first target. I have attempted to be as optimal as -possible, but there remains much room for improvement. - -I have attempted to make the emulator as portable as possible. One of -the problems is with leading underscores on kernel symbols. Elf -kernels have no leading underscores, a.out compiled kernels do. I -have attempted to use the C_SYMBOL_NAME macro wherever this may be -important. - -Another choice I made was in the file structure. I have attempted to -contain all operating system specific code in one module (fpmodule.*). -All the other files contain emulator specific code. This should allow -others to port the emulator to NetBSD for instance relatively easily. - -The floating point operations are based on SoftFloat Release 2, by -John Hauser. SoftFloat is a software implementation of floating-point -that conforms to the IEC/IEEE Standard for Binary Floating-point -Arithmetic. As many as four formats are supported: single precision, -double precision, extended double precision, and quadruple precision. -All operations required by the standard are implemented, except for -conversions to and from decimal. We use only the single precision, -double precision and extended double precision formats. The port of -SoftFloat to the ARM was done by Phil Blundell, based on an earlier -port of SoftFloat version 1 by Neil Carson for NetBSD/arm32. - -The file README.FPE contains a description of what has been implemented -so far in the emulator. The file TODO contains a information on what -remains to be done, and other ideas for the emulator. - -Bug reports, comments, suggestions should be directed to me at -<scottb@netwinder.org>. General reports of "this program doesn't -work correctly when your emulator is installed" are useful for -determining that bugs still exist; but are virtually useless when -attempting to isolate the problem. Please report them, but don't -expect quick action. Bugs still exist. The problem remains in isolating -which instruction contains the bug. Small programs illustrating a specific -problem are a godsend. - -Legal Notices -------------- - -The NetWinder Floating Point Emulator is free software. Everything Rebel.com -has written is provided under the GNU GPL. See the file COPYING for copying -conditions. Excluded from the above is the SoftFloat code. John Hauser's -legal notice for SoftFloat is included below. - -------------------------------------------------------------------------------- - -SoftFloat Legal Notice - -SoftFloat was written by John R. Hauser. This work was made possible in -part by the International Computer Science Institute, located at Suite 600, -1947 Center Street, Berkeley, California 94704. Funding was partially -provided by the National Science Foundation under grant MIP-9311980. The -original version of this code was written as part of a project to build -a fixed-point vector processor in collaboration with the University of -California at Berkeley, overseen by Profs. Nelson Morgan and John Wawrzynek. - -THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE. Although reasonable effort -has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT -TIMES RESULT IN INCORRECT BEHAVIOR. USE OF THIS SOFTWARE IS RESTRICTED TO -PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY -AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE. -------------------------------------------------------------------------------- diff --git a/Documentation/arm/nwfpe/todo.rst b/Documentation/arm/nwfpe/todo.rst deleted file mode 100644 index 393f11b14540..000000000000 --- a/Documentation/arm/nwfpe/todo.rst +++ /dev/null @@ -1,72 +0,0 @@ -TODO LIST -========= - -:: - - POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power - RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power - POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2) - - LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10 - LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e - EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent - SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine - COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine - TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent - ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine - ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine - ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent - -These are not implemented. They are not currently issued by the compiler, -and are handled by routines in libc. These are not implemented by the FPA11 -hardware, but are handled by the floating point support code. They should -be implemented in future versions. - -There are a couple of ways to approach the implementation of these. One -method would be to use accurate table methods for these routines. I have -a couple of papers by S. Gal from IBM's research labs in Haifa, Israel that -seem to promise extreme accuracy (in the order of 99.8%) and reasonable speed. -These methods are used in GLIBC for some of the transcendental functions. - -Another approach, which I know little about is CORDIC. This stands for -Coordinate Rotation Digital Computer, and is a method of computing -transcendental functions using mostly shifts and adds and a few -multiplications and divisions. The ARM excels at shifts and adds, -so such a method could be promising, but requires more research to -determine if it is feasible. - -Rounding Methods ----------------- - -The IEEE standard defines 4 rounding modes. Round to nearest is the -default, but rounding to + or - infinity or round to zero are also allowed. -Many architectures allow the rounding mode to be specified by modifying bits -in a control register. Not so with the ARM FPA11 architecture. To change -the rounding mode one must specify it with each instruction. - -This has made porting some benchmarks difficult. It is possible to -introduce such a capability into the emulator. The FPCR contains -bits describing the rounding mode. The emulator could be altered to -examine a flag, which if set forced it to ignore the rounding mode in -the instruction, and use the mode specified in the bits in the FPCR. - -This would require a method of getting/setting the flag, and the bits -in the FPCR. This requires a kernel call in ArmLinux, as WFC/RFC are -supervisor only instructions. If anyone has any ideas or comments I -would like to hear them. - -NOTE: - pulled out from some docs on ARM floating point, specifically - for the Acorn FPE, but not limited to it: - - The floating point control register (FPCR) may only be present in some - implementations: it is there to control the hardware in an implementation- - specific manner, for example to disable the floating point system. The user - mode of the ARM is not permitted to use this register (since the right is - reserved to alter it between implementations) and the WFC and RFC - instructions will trap if tried in user mode. - - Hence, the answer is yes, you could do this, but then you will run a high - risk of becoming isolated if and when hardware FP emulation comes out - - -- Russell. |