ack/mach/m68020/libem/dvi8.s
George Koehler e867861f6d Add 8-byte long long for linux68k.
Add rules for 8-byte integers to m68020 ncg.  Add 8-byte long long to
ACK C on linux68k.  Enable long-long tests for linux68k.  The tests
pass in our emulator using musahi; I don't have a real 68k processor
and haven't tried other emulators.

Still missing are conversions between 8-byte integers and any size of
floats.  The long-long tests don't cover these conversions, and our
emulator can't do floating-point.

Our build always enables TBL68020 and uses word size 4.  Without
TBL68020, 8-byte multiply and divide are missing.  With word size 2,
some conversions between 2-byte and 8-byte integers are missing.

Fix .cii in libem, which didn't work when converting from 1-byte or
2-byte integers.  Now .cii and .cuu work, but also add some rules to
skip .cii and .cuu when converting 8-byte integers.  The new rule for
loc 4 loc 8 cii `with test_set4` exposes a bug: the table may believe
that the condition codes test a 4-byte register when they only test a
word or byte, and this incorrect test may describe an unsigned word or
byte as negative.  Another rule `with exact test_set1+test_set2` works
around the bug by ignoring the negative flag, because a zero-extended
word or byte is never negative.

The old rules for comparison and logic do work with 8-byte integers
and bitsets, but add some specific 8-byte rules to skip libem calls or
loops.  There were no rules for 8-byte arithmetic, shift, or rotate;
so add some.  There is a register shortage, because the table requires
preserving d3 to d7, leaving only 3 data registers (d0, d1, d2) for
8-byte operations.  Because of the shortage, the code may move data to
an address register, or read a memory location more than once.

The multiplication and division code are translations of the i386
code.  They pass the tests, but might not give the best performance on
a real 68k processor.
2019-09-24 13:32:17 -04:00

35 lines
667 B
ArmAsm

.define .dvi8
.sect .text
.sect .rom
.sect .data
.sect .bss
yh=8
yl=12
xh=16
xl=20
! .dvi8 yields d0:d1 = quotient from x / y
.sect .text
.dvi8:
move.l d3, -(sp) ! preserve caller's d3
clr.l d2 ! d2 = 0, non-negative result
move.l (xh, sp), d0 ! d0 for .divrem8
bge 1f
move.l #1, d2 ! d2 = 1, negative result
neg.l (xl, sp)
negx.l d0 ! x = absolute value
1: move.l (yh, sp), d1 ! d1 for .divrem8
bge 1f
bchg #0, d2 ! flip sign of result
neg.l (yl, sp)
negx.l d1 ! y = absolute value
1: move.l d2, -(sp)
jsr (.divrem8)
move.l (sp)+, d2
beq 1f ! branch unless result < 0
neg.l d1
negx.l d0 ! negate quotient d0:d1
1: move.l (sp)+, d3
rtd #16