Test for cpu_forwarded->test_forwarded_arith fails

[jlusiardi]

There seems to be an issue while running the test bench:

The program should store 8 into mem address 123.

The check is kind of strange:

  cout << "top->MEM[123] = " << ((int)top->MEM[1000]) << endl;
  assert(top->MEM[123] == ((8 + 1000) + 1000));

Complete output of test:

make: Entering directory '/home/jlusiardi/Dokumente/src/TinyCPU_orig/obj_dir'
make: 'Vcpu_forwarded' is up to date.
make: Leaving directory '/home/jlusiardi/Dokumente/src/TinyCPU_orig/obj_dir'
Testing arithmetic result forwarding
Instruction being issued  = 00000000000000000000000000000000
decode_ireg_out           = 00000000000000000000000000000000
execute_ireg_out          = 00000000000000000000000000000000
memory_ireg_out           = 00000000000000000000000000000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
Instruction being issued  = 00000000000000000000000000000000
decode_ireg_out           = 00000000000000000000000000000000
execute_ireg_out          = 00000000000000000000000000000000
memory_ireg_out           = 00000000000000000000000000000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 0
forwarded alu result     =          0
Memory read address 0          0
Memory read address 1          0
Instruction being issued  = 00001000000000000100000000000000
decode_ireg_out           = 00000000000000000000000000000000
execute_ireg_out          = 00000000000000000000000000000000
memory_ireg_out           = 00000000000000000000000000000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 0
forwarded alu result     =          0
Memory read address 0          1
Memory read address 1          0
Instruction being issued  = 00001000000111110100000001000000
decode_ireg_out           = 00001000000000000100000000000000
execute_ireg_out          = 00000000000000000000000000000000
memory_ireg_out           = 00000000000000000000000000000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 1
operand 1 written by exe = 1
forwarded alu result     =          0
Memory read address 0          2
Memory read address 1          0
Instruction being issued  = 00101000000000100010000110000000
decode_ireg_out           = 00001000000111110100000001000000
execute_ireg_out          = 00001000000000000100000000000000
memory_ireg_out           = 00000000000000000000000000000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 1
forwarded alu result     =          0
Memory read address 0          3
Memory read address 1          0
Instruction being issued  = 00101000010001000011001010000000
decode_ireg_out           = 00101000000000100010000110000000
execute_ireg_out          = 00001000000111110100000001000000
memory_ireg_out           = 00001000000000000100000000000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 1
forwarded alu result     =          0
Memory read address 0          4
Memory read address 1          0
Writing          8 to register  0

Instruction being issued  = 00001000000000111101100001000000
decode_ireg_out           = 00101000010001000011001010000000
execute_ireg_out          = 00101000000000100010000110000000
memory_ireg_out           = 00001000000111110100000001000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 0
forwarded alu result     =          0
Memory read address 0          5
Memory read address 1          0
Writing       1000 to register  1

Instruction being issued  = 00011000000000100000000000000000
decode_ireg_out           = 00001000000000111101100001000000
execute_ireg_out          = 00101000010001000011001010000000
memory_ireg_out           = 00101000000000100010000110000000
read_data_0               =          0
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 1
forwarded alu result     =          0
Memory read address 0          6
Memory read address 1          0
Writing          0 to register  2

Instruction being issued  = 00000000000000000000000000000000
decode_ireg_out           = 00011000000000100000000000000000
execute_ireg_out          = 00001000000000111101100001000000
memory_ireg_out           = 00101000010001000011001010000000
read_data_0               =          8
read_data_1               =          0
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 0
forwarded alu result     =          8
Memory read address 0          7
Memory read address 1          0
Writing          0 to register  3

Instruction being issued  = 00000000000000000000000000000000
decode_ireg_out           = 00000000000000000000000000000000
execute_ireg_out          = 00011000000000100000000000000000
memory_ireg_out           = 00001000000000111101100001000000
read_data_0               =          8
read_data_1               =       1000
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 0
forwarded alu result     =       1000
Memory read address 0          8
Memory read address 1          8
Writing 00000000000000000000000000001000 to memory address 00000000000000000000000000000000
Writing        123 to register  1

Instruction being issued  = 00000000000000000000000000000000
decode_ireg_out           = 00000000000000000000000000000000
execute_ireg_out          = 00000000000000000000000000000000
memory_ireg_out           = 00011000000000100000000000000000
read_data_0               =          8
read_data_1               =       1000
stall                     = 0
squash                    = 0
operand 0 written by exe = 0
operand 1 written by exe = 0
forwarded alu result     =       1000
Memory read address 0          9
Memory read address 1          8
top->MEM[123] = 0
Vcpu_forwarded: ../cpu_forwarded_main.cpp:256: void test_forwarded_arith(int, char**): Assertion `top->MEM[123] == ((8 + 1000) + 1000)' failed.
Aborted
ERROR: cpu_forwarded tests failed
Traceback (most recent call last):
  File "test_bench.py", line 10, in <module>
    build_module('cpu_forwarded', '-Icommon -Icpu_forwarded')
  File "/home/jlusiardi/Dokumente/src/TinyCPU_orig/testbench_utils.py", line 35, in build_module
    build_module_with_main(mod_name, mod_name + '_main.cpp', flags)
  File "/home/jlusiardi/Dokumente/src/TinyCPU_orig/testbench_utils.py", line 32, in build_module_with_main
    assert(False)
AssertionError

[jlusiardi]

Ok, I found https://www.dillonbhuff.com/?p=1558 stating that the forwarded "version is a pipelined CPU with forwarding of operands to reduce stalling. It is unfinished.".

So unclear if close is correct here?

[dillonhuff]

I would just leave it open. If I do eventually find time to deal with this problem I will close the issue.