813 lines
21 KiB
Plaintext
813 lines
21 KiB
Plaintext
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PSIM - model the PowerPC environment
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Copyright (C) 1994-1996, Andrew Cagney <cagney@highland.com.au>.
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----------------------------------------------------------------------
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Building PSIM
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This file describes how to build the program PSIM
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o Walk through a basic build
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o Discussion of PSIM's components and
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how they relate to the build process
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o Detailed description of each of PSIM's
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compile time configuration options
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----------------------------------------------------------------------
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BUILDING PSIM:
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PSIM 1.0.2 is included in GDB-4.16. To build PSIM you will need the
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following:
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gdb-4.16.tar.gz Available from your favorite GNU
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ftp site
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gcc GCC version two includes suport
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for long long (64bit integer)
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arrithemetic which PSIM uses. Hence
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it is recommended that you build PSIM
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using GCC.
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Method:
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1. Unpack gdb
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$ cd .../scratch
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$ gunzip < gdb-4.16.tar.gz | tar xf -
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2. Configure gdb
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First consult the gdb documentation
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$ cd .../scratch
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$ cd gdb-4.16
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$ more README
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$ more gdb/README
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then something like (I assume SH):
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$ CC=gcc ./configure \
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--enable-sim-powerpc \
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--target=powerpc-unknown-eabi \
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--prefix=/applications/psim
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4. Build (again specifying GCC)
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$ make CC=gcc
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alternatively, if you are short on disk space or only
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want to build the simulator:
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$ ( cd libiberty && make CC=gcc )
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$ ( cd bfd && make CC=gcc )
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$ ( cd sim/ppc && make CC=gcc )
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5. Install
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$ make CC=gcc install
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or just
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$ cp gdb/gdb ~/bin/powerpc-unknown-eabisim-gdb
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$ cp sim/ppc/run ~/bin/powerpc-unknown-eabisim-run
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----------------------------------------------------------------------
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UPDATING PSIM:
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A PSIM is an ongoing development. Occasional snapshots which both contain new
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features and fix old bugs are made available. See the ftp directory:
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ftp://ftp.ci.com.au/pub/psim/beta
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or ftp://cambridge.cygnus.com/pub/psim/beta
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for the latest version. To build/install one of these snapshots, you
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replace the sim/ppc found in the gdb archive with with one from the
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snapshot. Then just re-configure and rebuild/install.
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Procedure:
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0. A starting point
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$ cd gdb-4.16
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1. Remove the old psim directory
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$ mv sim/ppc sim/old.ppc
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2. Unpack the new one
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$ gunzip < ../psim-NNNNNN.tar.gz | tar tf -
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$ gunzip < ../psim-NNNNNN.tar.gz | tar tf -
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3. Reconfigure/rebuild (as seen above):
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$ CC=gcc ./configure \
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--enable-sim-powerpc \
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--target=powerpc-unknown-eabi \
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--prefix=/applications/psim
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$ make CC=gcc
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----------------------------------------------------------------------
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UPDATES TO GDB:
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From time to time, problems involving the integration of PSIM into gdb
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are found. While eventually each of these problems is resolved there
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can be periouds during which a local hack may be needed.
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At the time of writing the following were outstanding:
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ATTACH command:
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ftp://ftp.ci.com.au/pub/psim/gdb-4.15+attach.diff.gz
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or ftp://cambridge.cygnus.com/pub/psim/gdb-4.15+attach.diff.gz
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PSIM, unlike the other simulators found in GDB, is able to load
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the description of a target machine (including the initial
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state of all processor registers) from a file.
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Unfortunatly GDB does not yet have a standard command that
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facilitates the use of this feature. Until such a command is
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added, the patch (hack?) gdb-4.15+attach.diff.gz can be used to
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extend GDB's attach command so that it can be used to initialize
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the simulators configuration from a file.
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----------------------------------------------------------------------
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RUNNING PROGRAMS:
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See the file:
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ftp://ftp.ci.com.au/pub/psim/RUN
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or ftp://cambridge.cygnus.com/pub/psim/RUN
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----------------------------------------------------------------------
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COMPILE TIME CONFIGURATION OPTIONS:
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PSIM's compile time configuration is controlled by autoconf. PSIM's
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configure script recognises options of the form:
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--enable-sim-<option>[=<val>]
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And can be specified on the configure command line (at the top level
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of the gdb directory tree) vis:
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$ cd gdb-4.15
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$ CC=gcc ./configure \
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--target=powerpc-unknown-eabisim \
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--prefix=/applications/psim \
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--enable-sim-inline
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$ make CC=gcc
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For a brief list of PSIM's configuration options, configure --help
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will list them vis:
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$ cd sim/ppc
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$ ./configure --help
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Each PSIM specific option is discussed in detail below.
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--enable-sim-cflags=<opts>
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Specify additional C compiler flags that are to be used when compiling
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just PSIM.
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PSIM places heavy demands on both the host machine and its C compiler. So that
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the builder has better control over the compiler the above option can be used
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to pass additional options to the compiler while PSIM is being built.
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Ex: No debug information
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PSIM can be built with everything inline. Unfortunately, because of
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all the debugging information generated the C compiler can grow very
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very large as a result. For GCC, the debug information can be
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restricted with the `-g0' option. To specify that this option should
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be include in the CFLAGS when compiling the psim source code use:
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--enable-sim-cflags=-g0
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Ex: Additional optimization flags
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A significant gain in performance can be achieved by tuning the
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optimization flags passed to the C compiler. For instance on an x86
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you may consider:
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--enable-sim-cflags='-g0 -O2 -fno-strength-reduce -f...'
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--enable-sim-warnings=<flags>
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Turn on additional GCC specific checks.
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Some hosts (NetBSD, Linux, Solaris-2.5) have complete header files
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that include correct prototypes for all library functions. On such
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hosts, PSIM can be built with many more than the standard C checks
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enabled. The option --enable-sim-warnings controls this.
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Ex: Default warnings
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With just --enable-sim-warnings, the following -W options are enabled:
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-Werror -Wall -Wpointer-arith -Wmissing-prototypes.
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--enable-sim-opcode=which
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Specify the file containing the rules for generating the instruction
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decode and execute functions from the file ppc-instructions.
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The form of the instruction decode and execute functions is controlled
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by an opcode table. It specifies: the combination of switch
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statements and jump tables to use when decoding an instruction and how
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much of each instruction should be decoded before calling the
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instruction execute function.
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PSIM includes a number of opcode tables:
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psim-opcode-simple
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Generates a small compact two level switch statement
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that will compile quickly and run reasonably fast.
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This may be useful on a small machine.
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psim-opcode-complex
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(the default) A fairly aggressive instruction decode
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table that includes the breaking out of a number
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of special instruction cases (eg RA==0 vs RA!=0).
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psim-opcode-flat
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Identical to complex except a switch statement
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is used. Ideal for when the icache is being
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disabled.
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psim-opcode-stupid
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In addition to the instruction decodes performed
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by psim-opcode-complex, this also full decodes mtspr,
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mfspr, and branch instructions. The table generated
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is very large and, as a consequence, only performs
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well on machines with large caches.
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ppc-opcode-test-1
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ppc-opcode-test-2
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Generate test (but workable) tables. These exercise
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PSIM's ability to generate instruction decode functions
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that are a combination of jump-tables and switch statements.
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The program igen generates the instruction tables from the opcode
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table and the ppc-instruction table.
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--enable-sim-switch
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Enable/disable the use of a switch statement when looking up the
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attributes of a SPR register.
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The PowerPC architecture defines a number of Special Purpose Registers
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(SPR's). Associated with each of these registers are a number of
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attributes (such as validity or size) which the instructions
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mtspr/mfspr query as part of their execution.
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For PSIM, this information is kept in a table (ppc-spr-table). The
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program dgen converts this table into lookup routines (contained in
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the generated files spreg.h spreg.c) that can be used to query an
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SPR's attributes. Those lookup routines are either implemented as
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a table or alternatively as a number of switch statements:
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spr_table spr_info[] = { .... };
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int spr_length(sprs spr) { return spr_info[spr].length; }
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vs
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int spr_length(sprs spr) { switch (spr) { case ..: return ..; } }
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In general the first implementation (a table) is the most efficient.
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It may, however, prove that when performing an aggressive optimization
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where both the SPR is known and the above function is being inlined
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(with the consequence that GCC can eliminate the switch statement)
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that the second choice is improves performance.
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In practice, only a marginal (if any benefit) has ever been seen.
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--enable-sim-duplicate
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Create a duplicate copy of each instruction function hardwiring
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instruction fields that would have otherwise have been variable.
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As discussed above, igen outputs a C function generated from the file
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ppc-instructions (using the opcode rules) for each of the
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instructions. Thus multiple entries in the instruction decode tables
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may be pointing back at the same function. Enabling duplicate, will
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result in psim creating a duplicate of the instruction's function for
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each different entry in the instruction decode tables.
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For instance, given the branch instruction:
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0.19,6.BO,11.BI,16./,21.528,31.LK
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...
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if (LK) LR = (spreg)IEA(CIA + 4);
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...
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igen as part of its instruction lookup table may have generated two
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different entries - one for LK=0 and one for LK=1. With duplicate
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enabled, igen outputs (almost) duplicate copies of branch function,
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one with LK hardwired to 0 and one with LK hardwired to 1.
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By doing this the compiler is provided with additional information that
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will allow it possibly eliminate dead code. (such as the assignment
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to LK if LR==0).
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Ex: default
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Because this feature is such a big win, --enable-sim-duplicate is
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turned on by default.
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Ex: A small machine
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Only rarely (eg on a very small host) would this feature need to be
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disabled (using: --disable-sim-duplicate).
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--enable-sim-filter=rule
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Include/exclude PowerPC instructions that are specific to a particular
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implementation.
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Some of the PowerPC instructions included in the file ppc-instructions
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are limited to certain specific PPC implementations. For instance,
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the instruction:
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0.58,6.RT,11.RA,16.DS,30.2:DS:64::Load Word Algebraic
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Is only valid for the 64bit architecture. The enable-sim-filter flag
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is passed to igen so that it can `filter out' any invalid
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instructions. The filter rule has the form:
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-f <name>
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thus:
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--enable-sim-filter='-f 64'
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(the default) would filter out all 64bit instructions.
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Ex: Remove floating point instructions
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A given 32bit PowerPC implementation may not include floating point
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hardware. Consequently there is little point in including floating
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point instructions in the instruction table. The option:
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--enable-sim-filter='-f 64 -f f'
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will eliminate all floating point instructions from the instruction
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table.
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--enable-sim-icache=size
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Set the size of the cache used to hold decoded instructions.
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Psim executes instructions in two separate steps:
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o instruction fetch/decode
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o instruction execution
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For a given instruction, the first stage need only be executed once
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(the first time the instruction is encountered) while the second stage
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must be executed every time the program `executes' that instruction.
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Exploiting this, PSIM can maintain a cache of decoded instructions.
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It will then use the decoded instruction from the cache in preference
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to fetching/decoding the real instruction from memory.
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Ex: default
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Because this feature is normally such a big win, it is enabled by
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default (with the cache size set to 1024 entries).
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The 1024 entries equals 4096 bytes (or one page) of instructions.
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Larger caches can be used but with caution - PSIM does not check for
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address aliasing within its instruction cache.
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Ex: disable the cache
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There may be cases (for instance where the cache has a low hit rate)
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where the psim performs better with no instruction cache. For such
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situations, the cache can be disabled vis: --disable-sim-icache.
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--enable-sim-inline[=module]
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Specify the inlining of one or more modules.
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Many architectures (in particular the x86) suffer from a large
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function call overhead. By eliminating function calls (through
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inlining of functions) a large performance gain can be achieved.
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In PSIM, modules are inlined in one of two possible ways. Some
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modules (such as the byte swapping code) can be inlined into any
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module that calls them. Other modules, due to complex
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interdependencies, are only inlined as a group when compiling the
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external interface module psim.c.
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Ex: default
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By default the modules endian (handle be/le), bits (manipulate
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bit-fields within words), cpu (the processor object) and events
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(timers) are inlined in any module that calls them. This gives a
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reasonable performance gain with little additional compilation
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overhead.
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Ex: recommended --enable-sim-inline
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Assuming you machine is reasonably well configured, this option is
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highly recommended. On the x86 several orders of magnitude
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improvement in performance is possible.
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Ex: fine tuning
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The file std-config.h contains a detailed description of how the
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inlining works. Individual modules can be inlined by specifying them.
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For if you have a very large cache the model module could be inlined
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with:
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--enable-sim-inline=MODEL
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--enable-sim-bswap
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(x86 specific) Use the i486/P5/P6 byte swap instruction.
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PSIM contains generic byte swapping code. For the x86 (P[4-6]) PSIM
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can be built so that it uses the bswap instruction instead of relying
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on the compiler to generate byte swap code.
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Ex: default
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By default, when compiling with GCC-2 on an i486/P5/P6 the bswap
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instruction is used.
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--enable-sim-endian=endian
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Specify the byte order of the target.
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By default, PSIM is able to execute both big and little endian
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executables. As a consequence, every byte swap routine includes a
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test to see if the byte swap is really needed. By specifying the byte
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order of the target (and the host below) the need for this test can be
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eliminated.
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Clearly setting the byte order of the target is only useful when known
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before hand.
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--enable-sim-hostendain=end
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As above but for the host.
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Normally this option should not be needed. configure (autoconf) should
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determine the byte order of the host automatically. However if for
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some reason there is a problem, this option can be used to override
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autoconf.
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--enable-sim-smp=n
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Set the maximum number of processors that PSIM can model.
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Psim can model (with small limitation discussed else where) a
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multi-processor PowerPC environment. While the overhead of
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co-ordinating the execution of a number of processors is relatively
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small it is still significant when compared to handling only one
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processor.
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This option only sets the maximum number of processors that can be
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simulated. The number active during a given simulation run us
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determined at run time.
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Ex: default
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By default 5 processors are configured but only one is enabled.
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Additional processors can be enabled with the runtime option:
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-o '/openprom/options/smp 5'
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Ex: recommended
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Unless you intend studying multi-processor systems there is little reason for
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having PSIM configured with SMP support. Specifying:
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--disable-sim-smp
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or --enable-sim-smp=0
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will eliminate any SMP such as:
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for (cpu = 0; cpu < nr_cpus; cpu++)
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...
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--enable-sim-xor-endian=n
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Set the byte-size of the bus involved in the PowerPC's xor endian byte
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swapping.
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The PowerPC's implementation of BE/LE mode is different to what a
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programmer may first expect. The details of this implementation are
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discussed at length in PowerPC documentation.
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Ex: default
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By default this is configured with a value of 8 (the bus size of most
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60x processors).
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Ex: recommended
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Unless you are expecting to test/debug PowerPC be/le switching code
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this option is of little use and should be disabled:
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--disable-sim-xor-endian
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--enable-sim-bitsize=n
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Specify the bit size (32/64) of the PowerPC to be modelled.
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Note: By default 32 is specified. The implementation of the 64bit
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architecture is still under development.
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--enable-sim-hostbitsize=32|64
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As above but for the host.
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NOTE: Psim has yet to be built on a 64bit host.
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--enable-sim-env=env
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Hardwire the PowerPC environment being modelled (user, virtual or
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operating).
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The PowerPC architecture defines three different levels of compliance to its
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architectural specification. These environments are discussed in detail in
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PowerPC publications.
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user - normal user programs
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virtual - an extension of the user environment (includes timers)
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operating - kernel code
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Ex: default
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By default all three environments are supported.
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Ex: recommended
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If you only intend running psim with user (or operating) code then
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PSIM should be configured accordingly. For user code, it eliminates:
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support for timers and events and redundant VM calls.
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--enable-sim-timebase
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Enable/disable the time base register.
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The PowerPC architecture (virtual environment) includes a time base
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register. Maintaining that register incurs an overhead in
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performance that can be eliminated by eliminating time-base register
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support.
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Ex: default
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Normally this option is not used. Instead --enable-sim-env (above) us
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used to disable/enable features such as the timebase register.
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--enable-sim-alignment=align
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Control the PowerPC's memory access alignment restrictions.
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The PowerPC in LE mode only allows memory transfers of a correctly
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aligned size/address. The above option controls how misaligned
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accesses are handled.
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strict All accesses must be correctly aligned
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nonstrict Unaligned access allowed (the are split
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into a number of aligned accesses).
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Ex: default
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Unless otherwise specified PSIM will auto configure a BE program to
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allow miss-aligned accesses while a LE program will not.
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Ex: 604e
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The recently announced 604e processor allows miss-aligned accesses in both
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BE and LE modes. If modeling the 604e then you should specify:
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--enable-sim-alignment=nonstrict
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--enable-sim-trace
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Include code to trace PSIM's internal progress (also controlled by the
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-t option).
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Checking to see if a trace message should be output slows down a
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simulation. Disabling this option (--disable-sim-trace) eliminates
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completely that code.
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--enable-sim-assert
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Include the code that checks the correctness of parts of PSIM.
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Eliminating such code (--disable-sim-assert) eliminates internal
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consistency tests and their overhead.
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--enable-sim-reserved-bits
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Include code to check that the reserved fields of the instruction are
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zero.
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The PowerPC architecture defines certain fields of some instructions
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as reserved (`/'). By default, for each instruction, PSIM will check
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the reserved fields causing an invalid instruction exception if a
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field is invalid. Disabling this option eliminates this test. This
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is at the slight risk of PSIM treating an invalid instruction as
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valid.
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--enable-sim-float
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Include support for hardware floating point.
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--enable-sim-monitor=mon
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Include support for basic instruction counting.
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If you are not interested in the performance of either you program or
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the simulator then you can disable this option.
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--enable-sim-model=which
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Hardwire the processor that will be used as a reference when modeling
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execution units.
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--enable-sim-default-model=which
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Specify the processor of choice for the execution unit model.
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--enable-sim-model-issue
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Include support for the modeling of processor execution units.
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----------------------------------------------------------------------
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TYPICAL CONFIGURATION OPTIONS:
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VEA CODE ONLY:
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Here of note are:
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o ramp up the compiler options (some
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of the below are P5 specific).
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o disable anything not used
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CC=gcc ./configure \
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--prefix=/applications/psim \
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--target=powerpc-unknown-eabi \
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--enable-sim-powerpc \
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--enable-sim-warnings \
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--enable-sim-inline \
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--disable-sim-smp \
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--enable-sim-duplicate \
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--enable-sim-endian=big \
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--disable-sim-xor-endian \
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--enable-sim-env=user \
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--disable-sim-reserved-bits \
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--disable-sim-assert \
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--disable-sim-trace \
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--enable-sim-cflags='-g0,-O2,-fno-strength-reduce,-fomit-frame-pointer'
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OEA CODE ONLY:
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The key configuration changes are:
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o turn off the instruction cache. The overhead
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of flushing and reloading it is greater than
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not having a cache.
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o use a switch statement (ppc-opcode-flat) for
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the instruction decode and then (-O3) fully
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inline all functions.
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o --enable-sim-warnings is not present. GCC (2.7.2)
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gets confused by the instruction decode table
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generated by igen (contains a perfect switch)
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and, as a consequence, generates a bogus warning.
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CC=gcc ./configure \
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--prefix=/applications/psim \
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--target=powerpc-unknown-eabi \
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--enable-sim-powerpc \
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--enable-sim-inline \
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--disable-sim-smp \
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--enable-sim-duplicate \
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--enable-sim-endian=big \
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--disable-sim-xor-endian \
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--enable-sim-env=operating \
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--disable-sim-reserved-bits \
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--disable-sim-assert \
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--disable-sim-trace \
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--enable-sim-opcode=ppc-opcode-flat \
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--disable-sim-icache \
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--enable-sim-cflags='-g0,-O3,-fno-strength-reduce,-fomit-frame-pointer'
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