Re: [Iverilog-devel] VVP Performance boots

[Stephen W. <st...@ic...>]

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Stephen Williams wrote:
| Try modifying the vhtread_run() function in vthread.cc to include
| a simple print after the call to the opcode, like this:
|
| ~   bool rc = (cp->opcode)(thr, cp);
| ~   cerr << "thr pc=" << thr->pc << " bit4=" << thr->bits4 << endl;

OK, I'm seeing something interesting. The second %addi is not
working. Judging by the symptoms, it appears to be reading a
32'd0 from the thread where it should be reading a 32'd1.

~   %load/v 12, v0xa0296d8_0, 4; "small1"
pc=0x84469e0
bit4=64'b000000000000000000000000000000010001111111111111_0001_0001X010ZX10

~   %mov 32, 12, 4;
pc=0x84469f0
bit4=64'b0000000000000000000000000000_0001_0001111111111111_0001_0001X010ZX10

~   %mov 36, 0, 28;
pc=0x8446a00
bit4=64'b_0000000000000000000000000000_0001000111111111111100010001X010ZX10

~   %addi 32, 1, 32;
pc=0x8446a10
bit4=64'b_00000000000000000000000000000001_000111111111111100010001X010ZX10

The 32'd1 stays 32'd1 in the thread, and hence the loop.

We need to look more carefully at the of_ADDI instruction. The
most likely problem is the vector_to_array() call returning a
wrong value. Then we need to look closely at the lvb array that
is made up by from the immediate data. This is probably OK if
the first %addi created an addition. Then we also need to look
at the final result that is lva. That is probably OK (given the
initial lva and lvb) because the thread got modified with the
correct result after the first %addi.

Can you put a test print in of_ADDI that prints lva[0] and lvb[0]
right before the "for" loop in the of_ADDI instruction? I'm going
to best that lva!=0 and lva[1]==0 every time through the of_ADDI
instruction.
- --
Steve Williams                "The woods are lovely, dark and deep.
steve at icarus.com           But I have promises to keep,
http://www.icarus.com         and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."
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