PSIM - model a PowerPC platform
Copyright (C) 1994-1995, Andrew Cagney <cagney@highland.com.au>.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
This directory contains the source code to the program PSIM.
What is PSIM?
PSIM is an ANSI C program that implements an instruction
level model of the PowerPC architecture.
It can be configured to model various PowerPC platforms
and include:
o A user program environment (UEA) complete
with emulated system calls
to
o A hardware platform with several processors
interacting with each other and various
modeled hardware devices.
For each of these models PSIM is able perform a detailed
analysis of the machines performance.
Who would be interested in PSIM?
o the curious
Using psim, gdb, gcc and binutils the curious
user can contruct an environment that allows
them to play with PowerPC user programs with out
the need for real hardware.
o the analyst
PSIM includes many (contributed) monitoring
features which (unlike many other simulators)
do not come with a great penalty in performance.
Thus the performance analyst is able to use
this simulator to model the inpact of changes
to the system they are analysing. Be that
system a compiler or real hardware platform.
If PSIM doesn't monitor a components of interest,
the source code is freely available, and hence
there is no hinderance to changing things
to meet a specific analysts needs.
o the serious SW developer
PSIM models all three levels of the PowerPC
Architecture: UEA, VEA and OEA. Further,
the internal design is such that PSIM can
be extended to suport additional
development requirements. Such requirements
might include (for the UEA) a new Operating
System emulation through to (for the OEA)
a model of a different hardware platform.
What features does PSIM have?
Monitoring and modeling
PSIM includes (thanks to Michael Meissner)
a detailed model of the various PowerPC
implementations schedulers.
SMP
The PowerPC ISA defines SMP synchronizing instructions
this simulator models a limited subset of their
behavor. Consequently, if you limit code to the
use the modeled behavour, PSIM can be used to
model SMP PowerPC platforms.
People intending to use this system should study
the code implementing the lwarx etc instructions.
ENDIAN SUPORT
PSIM implements the PowerPC's big and little (xor
endian) modes and correctly simulates code that
switches between these two modes.
In addition, psim can model a true little-endian
machine.
ISA models (Instruction Set Architecture)
PSIM includes a model of the UEA, VEA and OEA. This
inclues the time base registers (VEA) and HTAB
and BATS (OEA).
In addition, a preliminary model of the 64 bit
PowerPC architecture is implemented.
Hardware
PSIM's internals are based around the concept
of a Device Tree. This tree intentionaly
resembles that of the Device Tree found in
OpenBoot firmware. PSIM is flexable enough
to allow the user to fully configure the
actual hardware model from a device tree
specification that is read in from a file.
A user can either run a program using one of
PSIM's built in hardware models specify a
custom hardware model that should be simulated.
A user is also able to quickly add a model
of new hardware devices so that they can be
included in a custom hardware model.
OS-Emulation
PSIM's UEA model includes emulation for UNIX system
calls.
PSIM's OEA model includes emulation of either:
o OpenBoot client interface
o MOTO's BUG interface.
Floating point
Preliminary suport for floating point is included.
What performance analysis measurements can PSIM perform?
Below is the output from a recent analysis run
(contributed by Michael Meissner):
For the following program:
long
simple_rand ()
{
static unsigned long seed = 47114711;
unsigned long this = seed * 1103515245 + 12345;
seed = this;
return this >> 8;
}
unsigned long int
random_bitstring ()
{
unsigned long int x;
int ran, n_bits;
int tot_bits = 0;
x = 0;
for (;;)
{
ran = simple_rand ();
n_bits = (ran >> 1) % 16;
tot_bits += n_bits;
if (n_bits == 0)
return x;
else
{
x <<= n_bits;
if (ran & 1)
x |= (1 << n_bits) - 1;
if (tot_bits > 8 * sizeof (long) + 6)
return x;
}
}
}
#define ABS(x) ((x) >= 0 ? (x) : -(x))
main ()
{
int i;
for (i = 0; i < 50000; i++)
{
unsigned long x, y;
x = random_bitstring ();
y = random_bitstring ();
if (sizeof (int) == sizeof (long))
goto save_time;
{ unsigned long xx = x, yy = y, r1, r2;
if (yy == 0) continue;
r1 = xx / yy;
r2 = xx % yy;
if (r2 >= yy || r1 * yy + r2 != xx)
abort ();
}
{ signed long xx = x, yy = y, r1, r2;
if ((unsigned long) xx << 1 == 0 && yy == -1)
continue;
r1 = xx / yy;
r2 = xx % yy;
if (ABS (r2) >= (unsigned long) ABS (yy) || (signed long) (r1 * yy + r2) != xx)
abort ();
}
save_time:
{ unsigned int xx = x, yy = y, r1, r2;
if (yy == 0) continue;
r1 = xx / yy;
r2 = xx % yy;
if (r2 >= yy || r1 * yy + r2 != xx)
abort ();
}
{ signed int xx = x, yy = y, r1, r2;
if ((unsigned int) xx << 1 == 0 && yy == -1)
continue;
r1 = xx / yy;
r2 = xx % yy;
if (ABS (r2) >= (unsigned int) ABS (yy) || (signed int) (r1 * yy + r2) != xx)
abort ();
}
{ unsigned short xx = x, yy = y, r1, r2;
if (yy == 0) continue;
r1 = xx / yy;
r2 = xx % yy;
if (r2 >= yy || r1 * yy + r2 != xx)
abort ();
}
{ signed short xx = x, yy = y, r1, r2;
r1 = xx / yy;
r2 = xx % yy;
if (ABS (r2) >= (unsigned short) ABS (yy) || (signed short) (r1 * yy + r2) != xx)
abort ();
}
{ unsigned char xx = x, yy = y, r1, r2;
if (yy == 0) continue;
r1 = xx / yy;
r2 = xx % yy;
if (r2 >= yy || r1 * yy + r2 != xx)
abort ();
}
{ signed char xx = x, yy = y, r1, r2;
r1 = xx / yy;
r2 = xx % yy;
if (ABS (r2) >= (unsigned char) ABS (yy) || (signed char) (r1 * yy + r2) != xx)
abort ();
}
}
exit (0);
}
Here is the current output generated with the -I switch on a 90 Mhz
pentium (the compiler used is the devlopment version of GCC with a new
scheduler replacing the old one):
CPU #1 executed 41,994 AND instructions.
CPU #1 executed 519,785 AND Immediate instructions.
CPU #1 executed 680,058 Add instructions.
CPU #1 executed 41,994 Add Extended instructions.
CPU #1 executed 921,916 Add Immediate instructions.
CPU #1 executed 221,199 Add Immediate Carrying instructions.
CPU #1 executed 943,823 Add Immediate Shifted instructions.
CPU #1 executed 471,909 Add to Zero Extended instructions.
CPU #1 executed 571,915 Branch instructions.
CPU #1 executed 1,992,403 Branch Conditional instructions.
CPU #1 executed 571,910 Branch Conditional to Link Register instructions.
CPU #1 executed 320,431 Compare instructions.
CPU #1 executed 471,911 Compare Immediate instructions.
CPU #1 executed 145,867 Compare Logical instructions.
CPU #1 executed 442,414 Compare Logical Immediate instructions.
CPU #1 executed 1 Condition Register XOR instruction.
CPU #1 executed 103,873 Divide Word instructions.
CPU #1 executed 104,275 Divide Word Unsigned instructions.
CPU #1 executed 132,510 Extend Sign Byte instructions.
CPU #1 executed 178,895 Extend Sign Half Word instructions.
CPU #1 executed 871,920 Load Word and Zero instructions.
CPU #1 executed 41,994 Move From Condition Register instructions.
CPU #1 executed 100,005 Move from Special Purpose Register instructions.
CPU #1 executed 100,002 Move to Special Purpose Register instructions.
CPU #1 executed 804,619 Multiply Low Word instructions.
CPU #1 executed 421,201 OR instructions.
CPU #1 executed 471,910 OR Immediate instructions.
CPU #1 executed 1,292,020 Rotate Left Word Immediate then AND with Mask instructions.
CPU #1 executed 663,613 Shift Left Word instructions.
CPU #1 executed 1,151,564 Shift Right Algebraic Word Immediate instructions.
CPU #1 executed 871,922 Store Word instructions.
CPU #1 executed 100,004 Store Word with Update instructions.
CPU #1 executed 887,804 Subtract From instructions.
CPU #1 executed 83,988 Subtract From Immediate Carrying instructions.
CPU #1 executed 1 System Call instruction.
CPU #1 executed 207,746 XOR instructions.
CPU #1 executed 23,740,856 cycles.
CPU #1 executed 10,242,780 stalls waiting for data.
CPU #1 executed 1 stall waiting for a function unit.
CPU #1 executed 1 stall waiting for serialization.
CPU #1 executed 1,757,900 times a writeback slot was unavilable.
CPU #1 executed 1,088,135 branches.
CPU #1 executed 2,048,093 conditional branches fell through.
CPU #1 executed 1,088,135 successful branch predictions.
CPU #1 executed 904,268 unsuccessful branch predictions.
CPU #1 executed 742,557 branch if the condition is FALSE conditional branches.
CPU #1 executed 1,249,846 branch if the condition is TRUE conditional branches.
CPU #1 executed 571,910 branch always conditional branches.
CPU #1 executed 9,493,653 1st single cycle integer functional unit instructions.
CPU #1 executed 1,220,900 2nd single cycle integer functional unit instructions.
CPU #1 executed 1,254,768 multiple cycle integer functional unit instructions.
CPU #1 executed 1,843,846 load/store functional unit instructions.
CPU #1 executed 3,136,229 branch functional unit instructions.
CPU #1 executed 16,949,396 instructions that were accounted for in timing info.
CPU #1 executed 871,920 data reads.
CPU #1 executed 971,926 data writes.
CPU #1 executed 221 icache misses.
CPU #1 executed 16,949,396 instructions in total.
Simulator speed was 250,731 instructions/second
What motivated PSIM?
As an idea, psim was first discussed seriously during mid
1994. At that time its main objectives were:
o good performance
Many simulators loose out by only providing
a binary interface to the internals. This
interface eventually becomes a bottle neck
in the simulators performance.
It was intended that PSIM would avoid this
problem by giving the user access to the
full source code.
Further, by exploiting the power of modern
compilers it was hoped that PSIM would achieve
good performance with out having to compromize
its internal design.
o practical portability
Rather than try to be portable to every
C compiler on every platform, it was decided
that PSIM would restrict its self to suporting
ANSI compilers that included the extension
of a long long type.
GCC is one such compiler, consequenly PSIM
should be portable to any machine running GCC.
o flexability in its design
PSIM should allow the user to select the
features required and customize the build
accordingly. By having the source code,
the compler is able to eliminate any un
used features of the simulator.
After all, let the compiler do the work.
o SMP
A model that allowed the simulation of
SMP platforms with out the large overhead
often encountered with such models.
PSIM achieves each of these objectives.
Is PSIM PowerPC Platform (PPCP) (nee CHRP) Compliant?
No.
Among other things it does not have an Apple ROM socket.
Can PSIM be configured so that it models a CHRP machine?
Yes.
PSIM has been designed with the CHRP spec in mind. To model
a CHRP desktop a user would need to add the following:
o An apple rom socket :-)
o Model of each of the desktop IO devices
(some may already be implemented).
o An OpenPIC (Open Programmable Interrupt
Controller) device. (it may by now be
implemented).
o RTAS (Run Time Abstraction Services).
o A fully populated device tree.
Is the source code available?
Yes.
The source code to PSIM is available under the terms of
the GNU Public Licence. This allows you to distribute
the source code for free but with certain conditions.
How do I build PSIM?
To build PSIM you will need the following files:
gdb-4.15.tar.gz From your favorite GNU ftp site.
I've also tested psim with
gdb-4.15.1. If you would prefer
a graphical development environment
then PSIM can also be built with
gdbtk.
ftp://ftp.ci.com.au/pub/clayton/README.pim
This file.
ftp://ftp.ci.com.au/pub/clayton/gdb-4.15+psim.diff.gz
Firstly this file contains a few
minor changes to gdb-4.15 so that it
will build PSIM as part of GDB.
ftp://ftp.ci.com.au/pub/clayton/gdb-4.15+note.diff.gz
Add suport for note sections (used
by OpenBoot PowerPC programs).
ftp://ftp.ci.com.au/pub/clayton/gdb-4.15+attach.diff.gz
Allow the gdb attach command to
work with simulators.
ftp://ftp.ci.com.au/pub/clayton/psim-960119.tar.gz
This contains the psim files proper.
gcc Again available from your favorite
GNU ftp site.
patch Sun's patch behaves a little wierd
and doesn't appear to like creating
empty files. You may want to consider
installing gnu's patch.
Procedure:
0. A starting point
$ ls -1
gdb-4.15+attach.diff.gz
gdb-4.15+note.diff.gz
gdb-4.15+psim.diff.gz
gdb-4.15+psim.diff.gz
gdb-4.15.tar.gz
psim-960119.tar.gz
1. Unpack gdb
$ gunzip < gdb-4.15.tar.gz | tar xf -
2. Change to the gdb directory, apply the psim patches and unpack
the psim files.
$ cd gdb-4.15
$ gunzip < ../gdb-4.15+psim.diff.gz | more
$ gunzip < ../gdb-4.15+psim.diff.gz | patch -p1
$ gunzip < ../gdb-4.15+psim-960119.tar.gz | tar tvf -
$ gunzip < ../gdb-4.15+psim-960119.tar.gz | tar xvf -
You may also want to consider applying the `attach' and
`note' patches that are available vis:
$ gunzip < ../gdb-4.15+attach.diff.gz | more
$ gunzip < ../gdb-4.15+attach.diff.gz | patch -p
$ gunzip < ../gdb-4.15+note.diff.gz | more
$ gunzip < ../gdb-4.15+note.diff.gz | patch -p
3. Configure gdb
$ more gdb/README
then something like (I assume SH):
$ CC=gcc ./configure --target=powerpc-unknown-eabisim
eabisim is needed as by default (because PSIM needs GCC) the
simulator is not built.
[If building with a more recent gdb snapshot then the
command:
$CC=gcc ./configure --enable-sim-powerpc
is used.]
4. Build
$ make CC=gcc
alternativly, if you are short on disk space or just want the
simulator built:
$ ( cd libiberty && make CC=gcc )
$ ( cd bfd && make CC=gcc )
$ ( cd sim/ppc && make CC=gcc )
5. Install
$ make CC=gcc install
or just
$ cp gdb/gdb ~/bin/powerpc-unknown-eabisim-gdb
$ cp sim/ppc/run ~/bin/powerpc-unknown-eabisim-run
Is there a more recent version of PSIM and if so, how would I build it?
A PSIM is an ongoing development, occasional snapshots
(that include new features) are made available. Several of
the more recent snapshots are:
<to-be-advised>
To build/install one of these snapshots, you replace the
current gdb/sim/ppc directory with the one in the update,
re-configure and rebuild.
Procedure:
0. A starting point
$ cd gdb-4.15
1. Remove the old psim directory
$ mv sim/ppc sim/old.ppc
2. Unpack the new one
$ gunzip < ../psim-960105.tar.gz | tar tf -
$ gunzip < ../psim-960105.tar.gz | tar tf -
3. Reconfig/rebuild (as seen above):
$ CC=gcc ./configure --target=powerpc-unknown-eabisim
$ make CC=gcc
Are there any example programs that can be run on PSIM?
Psim has a simple test suite that is used to ensure
that fixes do not introduce new bugs. This test suite
like psim is updated:
ftp://ftp.ci.com.au/pub/clayton/psim-test-960118.tar.gz
Prebuilt test programs for PSIM.
Includes examples of UEA, VEA and
OEA code.
Requires gcc-2.7.2 and binutils-2.6
to rebuild.
How do I use the simulator?
I assume that you've unpacked a psim-test archive.
1. As a standalone program
Print out the users environment:
$ powerpc-unknown-eabisim-run psim-test/uea/envp
Print out the arguments:
$ powerpc-unknown-eabisim-run psim-test/uea/argv a b c
Check that sbrk works:
$ powerpc-unknown-eabisim-run psim-test/uea/break
2. Example of running GDB:
The main thing to note is that before you can run the simulator
you must enable it. The example below illustrates this:
$ powerpc-unknown-eabisim-gdb psim-test/uea/envp
(gdb) target sim
(gdb) load
(gdb) break main
(gdb) run
.
.
.
3. Using a device tree as a description of a machine
(I assume that you have applied the attach bug).
$ cd psim-test/tree
$ powerpc-unknown-eabisim-gdb
(gdb) target sim
(gdb) attach device-tree
(gdb) run
or
$ cd psim-test/tree
$ powerpc-unknown-eabisim-run device-tree
Where do I send bugs or report problems?
There is a mailing list (subscribe through majordomo@ci.com.au) (that
is almost never used) at:
powerpc-psim@ci.com.au
If I get the ftp archive updated I post a note to that mailing list.
In addition your welcome to send bugs or problems either to me or to
that e-mail list.
Does PSIM have any limitations or problems?
See the file PROBLEMS (included in the distribution) for any
outstanding issues.
Who helped?
Thanks go to the following who each helped in their own
way:
Allen Briggs, Bett Koch, David Edelsohn, Gordon Irlam,
Michael Meissner, Bob Mercier, Richard Perini, Dale Rahn
Richard Stallman, Mitchele Walker
