PowerPC has a few hundred special-purpose registers. The assembler
had only accepted the names "xer", "lr", "ctr". Most programs use
only those three SPRs. If I add more names, they would almost never
get used, and they might conflict with labels.
I want to use "mfspr r3, 0x3f0" and "mtspr 0x3f0, r3" in
plat/qemu/boot.s to access register hid0 from supervisor mode.
Telling osx386 and osxppc to build and run their own tools, not to
reuse the tools from linux386 and linuxppc. This wastes time to build
identical tools, but it removes some bogus dependencies. OS X tools
had wrongly depended on Linux descr files and aelflod; now they don't.
Discussion in https://github.com/davidgiven/ack/pull/23
Until now, I was always doing chmod +x before running my files on the
Mac. Now files get created +x. There's no change when overwriting
an existing file. I needed to gmake clean my build to remove the
example programs without +x, so cvmach can create them with +x.
If I want to check for overflow, then I should check it before I do
base + incr, not after.
Now that I have no check, I am passing the overflowed base + incr to
brk1(), where it will probably fail the nbreak < segment check.
This manual is in the new mdoc(7) format. All existing ack manuals
use the old man(7) format. This might be a problem if someone can't
display mdoc(7) files.
The build system doesn't install the cvmach(6) manual; that might
happen later. The current build system installs manuals in two
different places, and doesn't install some manuals, so I don't know
what to do.
No change to linuxppc and qemuppc. They continue to run ego without
any descr file.
I copied m68020.descr to powerpc.descr and changed some numbers. My
numbers are guesses; I know little about PowerPC cycle counts, and
almost nothing about ego. This powerpc.descr causes most of the
example programs to shrink in size (without descr -> with descr):
65429 -> 57237 hilo_b.osxppc -8192
36516 -> 32420 hilo_c.osxppc -4096
55782 -> 51686 hilo_mod.osxppc -4096
20096 -> 20096 hilo_p.osxppc 0
8813 -> 8813 mandelbrot_c.osxppc 0
93355 -> 89259 paranoia_c.osxppc -4096
92751 -> 84559 startrek_c.osxppc -8192
(Each file has 2 Mach segments, then a symbol table. Each segment
takes a multiple of 4096 bytes. When the code shrinks, we lose a
multiple of 4096 bytes.)
I used "ack -mosxppc -O6 -c.so" to examine the assembly code for
hilo.mod and mandelbrot.c, both without and with descr. This reveals
optimizations made only with descr, from 2 ego phases: SP (stack
pollution) and RA (register allocation). In hilo.mod, SP deletes some
instructions that remove items from the stack. These items get
removed when the function returns. In both hilo.mod and mandelbrot.c,
RA moves some values into local variables, so ncg can make them into
register variables. This shrinks code size, probably because register
variables get preserved across function calls. More values stay in
registers, and ncg emits shorter code.
I believe that the ego descr file uses (time,space) tuples but the ncg
table uses (space,time) tuples. This is confusing. Perhaps I am
wrong, and some or all tuples are backwards. My time values are the
cycle counts in latency from the MPC7450 Reference Manual (but not
including complications like "store serialization").
In powerpc.descr, I give the cost for saving and restoring registers
as if I was using chains of stw and lwz instructions. Actually ncg
uses single stmw and lmw instructions with at least 2 instructions.
The (time,space) for stmw and lmw would be much less than the
(time,space) for chains of stw and lwz. But this ignores the pipeline
of the MPC7450. The chains of stw and lwz may run faster than stmw
and lmw in the pipeline, because the throughput may be better than the
latency. By using the wrong values for (time,space), I'm trying to
tell ego that stmw and lmw are not better than chains of stw and lwz.
This prevents the warning, "implicit declaration of function raise",
in programs that call raise(). I forgot to declare it because the
function raise() is in libc but the declaration goes in libsys.
David Given made top for PowerPC. Copy the asopt phase (running top)
from linuxppc to osxppc.
Remove CC_ALIGN=-Vr to become compatible with Apple's gcc. Apple uses
left adjustment for bitfields; the first bitfield is on the left side
(the big end), not the right side.
Remove unused variables C_LIB and OLD_C_LIB; the file libc-ansi.a
doesn't exist.
Change MACHOPT_F from -m10 to -m3. This means to use no more than 3
adds and shifts to optimize a multiply by a constant. I pick -m3
because -m4 can use too many instructions. At -m4, the compiler
rewrites
n * 14
as
s = n << 1
(s << 3) + (0 - s)
This means (n * 16 - n * 2), but even at ack -O6, the compiler doesn't
rewrite (a + (0 - b)) as (a - b). The compiler emits 5 instructions:
2 of rlinmw for 2 left shifts, then addi to load 0 in a register, subf
to subtract from that 0, then add. These 5 instructions cost 5 cycles
on the MPC7450, using the cycle counts from mach/powerpc/ncg/table.
At -m3, (n * 14) becomes 2 instructions: addi to load 14 in a register
and mullw to multiply. This also costs 5 cycles (because mullw costs
4 cycles), but uses less space.
This brings in David Given's PowerPC changes, including the addition
of the modern code generator (mcg) for PowerPC.
Resolve minor conflicts in top build.lua and util/led/main.c
Also add fstat() and lstat(). I don't #define the constants for
st_mode or d_type, but I provide enough to get the block size of a
file and to list the names in a directory. Some fields of struct stat
get truncated, see XXX in plat/osx/include/sys/stat.h.
In struct dirent, the inode field might be d_ino or d_fileno. I
picked d_ino because Apple's sys/dirent.h uses d_ino (but Apple's
manual pages use d_fileno).
was nearly useless; lots of fixes to qemuppc and pc86 sbrk(), which was broken;
change the pc86 console to echo output to the serial port (needed for running
tests on qemu).
standard library, because they never worked and come from an achingly old
version of the Pascal specification. Fix the implementations of New() and
Dispose() to use the standard C memory allocator rather than rolling their own
(also in C). Write test!
