docs/pypowersim.mdwn

   1 # Links
   2
   3 * <https://bugs.libre-soc.org/show_bug.cgi?id=758>
   4 * [Pypowersim](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/decoder/isa/pypowersim.py)
   5 * [Media directory](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=media;hb=HEAD)
   6 * [MP3 test directory](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=media/audio/mp3;hb=HEAD)
   7 * [Machine-readable executable Power ISA 3.0 pseudocode](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=openpower/isa;hb=HEAD)
   8
   9 # Prerequisite installation
  10
  11 pypowersim is part of the
  12 [openpower-isa](https://git.libre-soc.org/?p=openpower-isa.git;a=summary)
  13 repository.  It is easiest installed with the [[HDL_workflow/devscripts]].
  14
  15 *Note: installation time without following the scripts has typically taken
  16 new users 2-3 weeks. After much pain and failure, when they then follow the
  17 advice given (formerly ignored), they find it takes under 1 day*.
  18
  19 # Pypowersim Guide
  20
  21 These are multimedia tests intended to cover the inner loops of various
  22 Audio/Video CODECs (such as MP3) and this guide uses them as examples
  23 to demonstrate pypowersim's functionality.  Other examples also exist:
  24
  25 * [basic scalar integer](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=src/test/basic_pypowersim;hb=HEAD)
  26 * [basic scalar FP](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=src/test/basic_pypowersim_fp;hb=HEAD)
  27
  28 **Note 1:** This is a bare-metal simulator.
  29 There's no GUI, UART, or console. To check that the tests ran
  30 succesfully, you need to dump the memory contents and inspect the output.
  31
  32 **Note 2:** pypowersim is designed for ease-of-understanding of the Power
  33 ISA and as a tool to check that the Power ISA Specification itself is
  34 correct. For example, a python class
  35 [SelectableInt](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/decoder/selectable_int.py;hb=HEAD)
  36 has been created which understands IBM MSB0 ordering. Even
  37 a RADIX MMU has been implemented, 100% in python using IBM-sponsored
  38 [gem5-experimental](https://github.com/power-gem5/gem5/blob/gem5-experimental/src/arch/power/radixwalk.cc) work as a guide.  This
  39 *deliberate and conscious* design choice to focus on readability
  40 and understanding makes pypowersim extremely slow: an Intel i9 running
  41 at 4.8 ghz is only capable of 2,500 instructions per second.
  42
  43 # Pypowersim - PowerISA Simulator
  44
  45 Pypowersim is a PowerISA simulator written in Python. It includes
  46 the **exact** same
  47 [RADIX MMU](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/decoder/isa/radixmmu.py;hb=HEAD)
  48 support as
  49 [Microwatt](https://github.com/antonblanchard/microwatt/blob/master/mmu.vhdl).
  50 PowerISA binaries are decoded by an
  51 [ISA class instance](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/decoder/isa/caller.py;hb=HEAD).
  52 ISACaller utilises compiled machine-readable Power ISA 3.0
  53 pseudocode taken directly from the Power ISA Specification.
  54
  55 SVP64 binaries are also supported. Simulation is managed cycle by cycle,
  56 for instruction and memory debugging.
  57 Use of QEMU as a co-simulator is also supported for verifying the
  58 binaries run identically.
  59
  60 To find out about input arg information, run the script with "-h/--help"
  61 or no arguments to get the help message:
  62
  63 ```
  64 $ python3 openpower-isa/src/openpower/decoder/isa/pypowersim.py
  65 ```
  66
  67 # Tests
  68
  69
  70 The tests consist of running Pypowersim with several input arg's:
  71
  72 * ".gpr" text file for initialising the General Purpose (integer) Registers
  73 * ".spr" text file for initialising the Special Purpose Registers
  74 * Initialising the Program Counter
  75 * Loading given binaries into specified memory locations
  76 * Select which memory regions to dump to a file
  77 * Select the executable to run
  78
  79 There are other options available (such as initialising the Floating Point
  80 Registers).
  81 for
  82
  83 **Example GPR file**:
  84
  85 See <https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=media/audio/mp3/mp3_0.gpr;hb=HEAD>
  86
  87 This file sets the GPRs to explicit values prior to execution.
  88 This allows for example a function call's parameters, according
  89 to Power ISA
  90 [ABI calling convention](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=media/calling-conv;hb=HEAD),
  91 to be set conveniently and quickly, but
  92 more importantly without requiring execution of additional
  93 instructions.
  94
  95 In this example below the parameters point to areas of memory
  96 that are loaded or dumped, containing the input and output areas
  97 of the function.  They match up with the other parameters to the
  98 example script
  99
 100 ```
 101    1 # void ff_mpadsp_apply_window_float(float *synth_buf, float *window,
 102    2 #                                  int *dither_state, float *samples,
 103    3 #                                  ptrdiff_t incr);
 104    4 1: 0x8000        # stack pointer
 105    5 3: 0x600000      # param 1: float *sunth_buf     buf
 106    6 4: 0x700000      # param 2: float *window        win
 107    7 5: 0x800000      # param 3: int *dither_state    &unused
 108    8 6: 0x900000      # param 3: float *samples       out
 109    9 7: 1             # param 5: ptr_diff_t incr      1
 110 ```
 111
 112 **Example SPR file**
 113
 114 See <https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=media/common.spr;hb=HEAD>
 115
 116 This file sets SPRs to explicit values prior to execution. In this
 117 example Link Register LR is set to 0xffffffff which on completion
 118 of the function sets PC to an invalid out-of-bounds value causing
 119 program termination.
 120
 121 ```
 122   1 LR: 0xffffffff
 123 ```
 124
 125 **Example Execution**
 126
 127 See <https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=media/audio/mp3/mp3_0.sh;hb=HEAD>
 128
 129 The GPRs and SPRs above are loaded prior to execution, as is the
 130 sample data (at appropriate addresses matching the function parameters).
 131 After execution 128 bytes are dumped from address 0x900000.
 132
 133 ```
 134    1 #!/bin/sh -xe
 135    2
 136    3 pypowersim -g audio/mp3/mp3_0.gpr \
 137    4         -s common.spr \
 138    5         -p 0x20000000 \
 139    6         -l data/audio/mp3/mp3_0_data/buf${1}:0x600000 \
 140    7         -l data/audio/mp3/mp3_0_data/win0:0x700000 \
 141    8         -d ${2}:0x900000:128 \
 142    9         -i audio/mp3/mp3_0_apply_window_float.bin
 143 ```
 144
 145 # Before running the media tests
 146
 147 During development, the available opcodes may change.
 148 Make sure to update the auto-generated Python functions
 149 simulating the instructions. Also the audio data needs to be downloaded.
 150
 151 * run "pywriter". This is an installed utility, so should be in your PATH.
 152   It recompiles the machine-readable Power ISA pseudocode into
 153   executable python.
 154 * Download audio data. Use the Makefile inside "openpower-isa/media" to
 155  download the audio samples.
 156
 157 ```
 158 $ pywriter
 159 $ make wget
 160 ```
 161
 162 # Running both tests
 163
 164 Run the Makefile in the "openpower-isa/media" directory with "tests" arg:
 165
 166 ```
 167 $ make tests
 168 ```
 169
 170 All the debug will go to standard output, so you may wish to direct it to a
 171 log file (the file will be **big**!).
 172
 173 To suppress verbose debug log, uncomment "#export SILENCELOG = 1" in the
 174 Makefile or export it manually.
 175
 176 # Running "mp3_x" tests individually
 177
 178 Inside "openpower-isa/media" directory run:
 179
 180 ```
 181 $ ./audio/mp3/mp3_0.sh 0 out0
 182 ```
 183
 184 The "out0" file will be created in the "media" directory. Change the name
 185 if you don't want the second test to overwrite the results of the first.
 186
 187 # Checking results
 188
 189 If you run both tests through the makefile, the shell script
 190 automatically compares the input "sample0" file with the
 191 generated "out0" file.
 192
 193 For manual checking, you need to know where the "out" file is, and then
 194 use the "cmp" program to compare byte by byte the sample and output
 195 files.
 196
 197 ```
 198 $ cmp out0 data/audio/mp3/mp3_0_data/samples0
 199 ```
 200
 201 As is usual for UNIX commands no output indicates the files are identical.