Anshuman Khandual [khand...@linux.vnet.ibm.com] wrote: | On 10/16/2013 01:55 PM, David Laight wrote: | >> Implement instr_is_load_store_2_06() to detect whether a given instruction | >> is one of the fixed-point or floating-point load/store instructions in the | >> POWER Instruction Set Architecture v2.06. | > ... | | The op code encoding is dependent on the ISA version ? Does the basic load | and store instructions change with newer ISA versions ?
TBH, I don't know whether the encoding is dependent on the ISA version. We need this for a very narrow/specific purpose on Power7 _and_ did not want to set up expectations that it will work with all versions. Hence the horribly named function :-) | BTW we have got a | newer version for the ISA "PowerISA_V2.07_PUBLIC.pdf" here at power.org | | https://www.power.org/documentation/power-isa-version-2-07/ Yes, but on Power8 there is a bit in the SIER that tells us whether it is a load or store instruction. We use that and don't need to determine in software. Power7 does not have such a bit and we need this only for Power7. We are not targetting this "memory hierarchy" feature for Power6 or older processors. | | Does not sound like a good idea to analyse the instructions with functions | names which specify ISA version number. Besides, this function does not | belong to specific processor or platform. It has to be bit generic. | | >> +int instr_is_load_store_2_06(const unsigned int *instr) | >> +{ | >> + unsigned int op, upper, lower; | >> + | >> + op = instr_opcode(*instr); | >> + | >> + if ((op >= 32 && op <= 58) || (op == 61 || op == 62)) | >> + return true; | >> + | >> + if (op != 31) | >> + return false; | >> + | >> + upper = op >> 5; | >> + lower = op & 0x1f; | >> + | >> + /* Short circuit as many misses as we can */ | >> + if (lower < 3 || lower > 23) | >> + return false; | >> + | >> + if (lower == 3) { | >> + if (upper >= 16) | >> + return true; | >> + | >> + return false; | >> + } | >> + | >> + if (lower == 7 || lower == 12) | >> + return true; | >> + | >> + if (lower >= 20) /* && lower <= 23 (implicit) */ | >> + return true; | >> + | >> + return false; | >> +} | > | > I can't help feeling the code could do with some comments about | > which actual instructions are selected where. | | Yeah, I agree. At least which category of load-store instructions are | getting selected in each case. Like I mentioned in the other message, how about adding a couple of lines in the function header ? _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
