path: root/sim/ppc/README.psim

		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