[Libre-soc-bugs] [Bug 425] DIV overflow not being calculated correctly

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=425

--- Comment #12 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Luke Kenneth Casson Leighton from comment #10)

> actually the sim output might be wrong, here.  it should never be
> set to 0b1.  the two legal values are 0b00 and 0b11, NEVER 0b01.

it was wrong.  fixed.  

commit f25aad525dfc184b5a8407e52b62a499dfb182f4
Author: Luke Kenneth Casson Leighton <lkcl at lkcl.net>
Date:   Fri Jul 10 16:04:08 2020 +0100

    check for div_overflow equal to None rather than == 1


going through some more regression tests, it looks like we're out of the
woods.  the div_by_zero flag is not being propagated through the
pipeline stages to the output stage, that was shown by this test:

    def test_div_by_zero_1(self):
        lst = ["divw. 3, 1, 2"]
        initial_regs = [0] * 32
        initial_regs[1] = 0x1
        initial_regs[2] = 0x0
        self.run_tst_program(Program(lst), initial_regs)

i'll sort that now.

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