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I've gobe for my own mul algorithm for now, and it seems to work for small

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positive integers, but it probably needs fixing.
This commit is contained in:
Warren Toomey
2016-03-04 15:29:37 +10:00
parent 807fb56d35
commit 6f3008e8bd
1 changed files with 12 additions and 7 deletions
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tools/a7out
+12 -7
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@@ -555,6 +555,7 @@ sub eae {
# https://github.com/simh/simh/blob/master/PDP18B/pdp18b_cpu.c # https://github.com/simh/simh/blob/master/PDP18B/pdp18b_cpu.c
my $MB= $Mem[ $PC+1 ]; my $MB= $Mem[ $PC+1 ];
my $eae_ac_sign; my $eae_ac_sign;
dprintf("mul AC %06o by %06o (decimal %d by %d)\n", $AC, $MB, $AC, $MB);
if (($instruction & 0004000) && ($AC & SIGN)) { # IR<6> and minus? if (($instruction & 0004000) && ($AC & SIGN)) { # IR<6> and minus?
$eae_ac_sign = $LINK; # set eae_ac_sign $eae_ac_sign = $LINK; # set eae_ac_sign
@@ -565,18 +566,22 @@ sub eae {
my $oldlink= $LINK; my $oldlink= $LINK;
$LINK = 0; # Clear link $LINK = 0; # Clear link
foreach my $SC (1 .. $instruction & 077) { # Loop for SC times my $result= $AC * $MB;
$AC = $AC + $MB $AC= ($result >> 18) & MAXINT;
if ($MQ & 1); # MQ<17>? add $MQ= $result & MAXINT;
$MQ = ($MQ >> 1) | (($AC & 1) << 17);
$AC = $AC >> 1; # Shift AC'MQ right ## foreach my $SC (1 .. $instruction & 077) { # Loop for SC times
} ## $AC = $AC + $MB
## if ($MQ & 1); # MQ<17>? add
## $MQ = ($MQ >> 1) | (($AC & 1) << 17);
## $AC = $AC >> 1; # Shift AC'MQ right
## }
if ($eae_ac_sign ^ $oldlink) { # Result negative? if ($eae_ac_sign ^ $oldlink) { # Result negative?
$AC = $AC ^ MAXINT; $AC = $AC ^ MAXINT;
$MQ = $MQ ^ MAXINT; $MQ = $MQ ^ MAXINT;
} }
$PC++; $PC+=2;
return; return;
} }
printf( STDERR "PC %06o: Unknown eae instruction %06o\n", printf( STDERR "PC %06o: Unknown eae instruction %06o\n",