1TODO LIST 2========= 3 4:: 5 6 POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power 7 RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power 8 POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2) 9 10 LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10 11 LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e 12 EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent 13 SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine 14 COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine 15 TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent 16 ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine 17 ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine 18 ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent 19 20These are not implemented. They are not currently issued by the compiler, 21and are handled by routines in libc. These are not implemented by the FPA11 22hardware, but are handled by the floating point support code. They should 23be implemented in future versions. 24 25There are a couple of ways to approach the implementation of these. One 26method would be to use accurate table methods for these routines. I have 27a couple of papers by S. Gal from IBM's research labs in Haifa, Israel that 28seem to promise extreme accuracy (in the order of 99.8%) and reasonable speed. 29These methods are used in GLIBC for some of the transcendental functions. 30 31Another approach, which I know little about is CORDIC. This stands for 32Coordinate Rotation Digital Computer, and is a method of computing 33transcendental functions using mostly shifts and adds and a few 34multiplications and divisions. The ARM excels at shifts and adds, 35so such a method could be promising, but requires more research to 36determine if it is feasible. 37 38Rounding Methods 39---------------- 40 41The IEEE standard defines 4 rounding modes. Round to nearest is the 42default, but rounding to + or - infinity or round to zero are also allowed. 43Many architectures allow the rounding mode to be specified by modifying bits 44in a control register. Not so with the ARM FPA11 architecture. To change 45the rounding mode one must specify it with each instruction. 46 47This has made porting some benchmarks difficult. It is possible to 48introduce such a capability into the emulator. The FPCR contains 49bits describing the rounding mode. The emulator could be altered to 50examine a flag, which if set forced it to ignore the rounding mode in 51the instruction, and use the mode specified in the bits in the FPCR. 52 53This would require a method of getting/setting the flag, and the bits 54in the FPCR. This requires a kernel call in ArmLinux, as WFC/RFC are 55supervisor only instructions. If anyone has any ideas or comments I 56would like to hear them. 57 58NOTE: 59 pulled out from some docs on ARM floating point, specifically 60 for the Acorn FPE, but not limited to it: 61 62 The floating point control register (FPCR) may only be present in some 63 implementations: it is there to control the hardware in an implementation- 64 specific manner, for example to disable the floating point system. The user 65 mode of the ARM is not permitted to use this register (since the right is 66 reserved to alter it between implementations) and the WFC and RFC 67 instructions will trap if tried in user mode. 68 69 Hence, the answer is yes, you could do this, but then you will run a high 70 risk of becoming isolated if and when hardware FP emulation comes out 71 72 -- Russell. 73