[Libre-soc-bugs] [Bug 1115] rldimi "mb" offset by 1 bit

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=1115

--- Comment #3 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
start with this:

echo "rldimi. 3,4,56,8" >> /tmp/test.s

then run these:

pysvp64asm /tmp/test.s /tmp/py.s
powerpc64le-linux-gnu-as /tmp/py.s -o /tmp/test.o
powerpc64le-linux-gnu-objcopy -Obinary /tmp/test.o /tmp/bin.o
powerpc64le-linux-gnu-objdump -dr /tmp/test.o 
pysvp64dis -v /tmp/bin.o 

and the output is:

   0:   0f c2 83 78     rldimi. r3,r4,56,8
0f c2 83 78    rldimi. r3,r4,56,16
    spec
        rldimi. RA,RS,sh,mb Rc=1
    pcode
        n <- sh
        r <- ROTL64((RS), n)
        b <- mb[5] || mb[0:4]
        m <- MASK(b,  ¬n)
        RA <- r&m | (RA)& ¬m
    binary
        [0:8]   01111000
        [8:16]  10000011
        [16:24] 11000010
        [24:32] 00001111
    opcodes
        011110---------------------011-1
    PO
        011110
        0, 1, 2, 3, 4, 5
    XO
        011
        27, 28, 29
    Rc
        1
        31
    RA (scalar)
        00011
        11, 12, 13, 14, 15
    RS (scalar)
        00100
        6, 7, 8, 9, 10
    sh
        111000
        30, 16, 17, 18, 19, 20
    mb
        010000
        21, 22, 23, 24, 25, 26


now let's do "rldimi. r3,r4,56,32":

   0:   2f c0 83 78     rldimi. r3,r4,56,32
2f c0 83 78    rldimi. r3,r4,56,1
    spec
        rldimi. RA,RS,sh,mb Rc=1
    pcode
        n <- sh
        r <- ROTL64((RS), n)
        b <- mb[5] || mb[0:4]
        m <- MASK(b,  ¬n)
        RA <- r&m | (RA)& ¬m
    binary
        [0:8]   01111000
        [8:16]  10000011
        [16:24] 11000000
        [24:32] 00101111
    opcodes
        011110---------------------011-1
    PO
        011110
        0, 1, 2, 3, 4, 5
    XO
        011
        27, 28, 29
    Rc
        1
        31
    RA (scalar)
        00011
        11, 12, 13, 14, 15
    RS (scalar)
        00100
        6, 7, 8, 9, 10
    sh
        111000
        30, 16, 17, 18, 19, 20
    mb
        000001
        21, 22, 23, 24, 25, 26

and, ahhh mb has bit 0 in the wrong place.

it looks like Operand-Decode of mb is out

https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/test/shift_rot/shift_rot_cases.py;h=71a5ce#l159

damn, there's no "ExpectedResults".

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