Custom Search

Based on kernel version `4.3`. Page generated on `2015-11-02 12:43 EST`.

1 The following describes the current state of the NetWinder's floating point 2 emulator. 3 4 In the following nomenclature is used to describe the floating point 5 instructions. It follows the conventions in the ARM manual. 6 7 <S|D|E> = <single|double|extended>, no default 8 {P|M|Z} = {round to +infinity,round to -infinity,round to zero}, 9 default = round to nearest 10 11 Note: items enclosed in {} are optional. 12 13 Floating Point Coprocessor Data Transfer Instructions (CPDT) 14 ------------------------------------------------------------ 15 16 LDF/STF - load and store floating 17 18 <LDF|STF>{cond}<S|D|E> Fd, Rn 19 <LDF|STF>{cond}<S|D|E> Fd, [Rn, #<expression>]{!} 20 <LDF|STF>{cond}<S|D|E> Fd, [Rn], #<expression> 21 22 These instructions are fully implemented. 23 24 LFM/SFM - load and store multiple floating 25 26 Form 1 syntax: 27 <LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn] 28 <LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn, #<expression>]{!} 29 <LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn], #<expression> 30 31 Form 2 syntax: 32 <LFM|SFM>{cond}<FD,EA> Fd, <count>, [Rn]{!} 33 34 These instructions are fully implemented. They store/load three words 35 for each floating point register into the memory location given in the 36 instruction. The format in memory is unlikely to be compatible with 37 other implementations, in particular the actual hardware. Specific 38 mention of this is made in the ARM manuals. 39 40 Floating Point Coprocessor Register Transfer Instructions (CPRT) 41 ---------------------------------------------------------------- 42 43 Conversions, read/write status/control register instructions 44 45 FLT{cond}<S,D,E>{P,M,Z} Fn, Rd Convert integer to floating point 46 FIX{cond}{P,M,Z} Rd, Fn Convert floating point to integer 47 WFS{cond} Rd Write floating point status register 48 RFS{cond} Rd Read floating point status register 49 WFC{cond} Rd Write floating point control register 50 RFC{cond} Rd Read floating point control register 51 52 FLT/FIX are fully implemented. 53 54 RFS/WFS are fully implemented. 55 56 RFC/WFC are fully implemented. RFC/WFC are supervisor only instructions, and 57 presently check the CPU mode, and do an invalid instruction trap if not called 58 from supervisor mode. 59 60 Compare instructions 61 62 CMF{cond} Fn, Fm Compare floating 63 CMFE{cond} Fn, Fm Compare floating with exception 64 CNF{cond} Fn, Fm Compare negated floating 65 CNFE{cond} Fn, Fm Compare negated floating with exception 66 67 These are fully implemented. 68 69 Floating Point Coprocessor Data Instructions (CPDT) 70 --------------------------------------------------- 71 72 Dyadic operations: 73 74 ADF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - add 75 SUF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - subtract 76 RSF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse subtract 77 MUF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - multiply 78 DVF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - divide 79 RDV{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse divide 80 81 These are fully implemented. 82 83 FML{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast multiply 84 FDV{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast divide 85 FRD{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast reverse divide 86 87 These are fully implemented as well. They use the same algorithm as the 88 non-fast versions. Hence, in this implementation their performance is 89 equivalent to the MUF/DVF/RDV instructions. This is acceptable according 90 to the ARM manual. The manual notes these are defined only for single 91 operands, on the actual FPA11 hardware they do not work for double or 92 extended precision operands. The emulator currently does not check 93 the requested permissions conditions, and performs the requested operation. 94 95 RMF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - IEEE remainder 96 97 This is fully implemented. 98 99 Monadic operations: 100 101 MVF{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - move 102 MNF{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - move negated 103 104 These are fully implemented. 105 106 ABS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - absolute value 107 SQT{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - square root 108 RND{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - round 109 110 These are fully implemented. 111 112 URD{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - unnormalized round 113 NRM{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - normalize 114 115 These are implemented. URD is implemented using the same code as the RND 116 instruction. Since URD cannot return a unnormalized number, NRM becomes 117 a NOP. 118 119 Library calls: 120 121 POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power 122 RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power 123 POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2) 124 125 LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10 126 LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e 127 EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent 128 SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine 129 COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine 130 TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent 131 ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine 132 ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine 133 ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent 134 135 These are not implemented. They are not currently issued by the compiler, 136 and are handled by routines in libc. These are not implemented by the FPA11 137 hardware, but are handled by the floating point support code. They should 138 be implemented in future versions. 139 140 Signalling: 141 142 Signals are implemented. However current ELF kernels produced by Rebel.com 143 have a bug in them that prevents the module from generating a SIGFPE. This 144 is caused by a failure to alias fp_current to the kernel variable 145 current_set[0] correctly. 146 147 The kernel provided with this distribution (vmlinux-nwfpe-0.93) contains 148 a fix for this problem and also incorporates the current version of the 149 emulator directly. It is possible to run with no floating point module 150 loaded with this kernel. It is provided as a demonstration of the 151 technology and for those who want to do floating point work that depends 152 on signals. It is not strictly necessary to use the module. 153 154 A module (either the one provided by Russell King, or the one in this 155 distribution) can be loaded to replace the functionality of the emulator 156 built into the kernel.

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.