Commit Graph

13 Commits (master)

Author SHA1 Message Date
Paul Mackerras 20f49f06f8 multiply_tb: Fix multiply_tb.vhdl for the new multiplier interface
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
10 months ago
Lars Asplund 478b787c10 Replaced VHDL assert and report with VUnit checking and logging
The VUnit log package is a SW style logging framework in VHDL and the check package is an assertion library doing its error reporting with VUnit logging.
These testbenches don't use, and do not need, very advanced logging/checking features but the following was possible to improve

- Checking equality in VHDL can be quite tedious with a lot of type conversions and long message strings to explain the data received and what was expected.
  VUnit's check_equal procedure allow comparison between same or similar types and automatically create the error message for you.
- The code has report statements used for testbench progress reporting and debugging. These were replaced with the info and debug procedures.
  info logs are visible by default while debug is not. This means that debug logs don't have to be commented, which they are now, when not used.
  Instead there is a show procedure making debug messages visible. The show procedure has been commented to hide the debug messages but a more elegant
  solution is to control visibility from a generic and then set that generic from the command line. I've left this as a TODO but the run script allow you to
  extend the standard CLI of VUnit to add new options and you can also set generics from the run script.
- VUnit log messages are color coded if color codes are supported by the terminal. It makes it quicker to spot messages of different types when there are many log messages.
  Error messages will always be made visible on the terminal but you must use the -v (verbose) to see other logs.
- Some tests have a lot of "metvalue detected" warning messages from the numeric_std package and these clutter the logs when using the -v option. VUnit has a simulator independent
  option allowing you to suppress those messages. That option has been enabled.

Signed-off-by: Lars Asplund <lars.anders.asplund@gmail.com>
2 years ago
Lars Asplund 0940b8a9d3 Organized VUnit testbenches into test cases.
Several of the testbenches have stimuli code divided into sections preceded with a header comment explaining
what is being tested. These sections have been made into VUnit test cases. The default behavior of VUnit is
to run each test case in a separate simulation which comes with a number of benefits:

* A failing test case doesn't prevent other test cases to be executed
* Test cases are independent. A test case cannot fail as a side-effect to a problem with another test case
* Test execution can be more parallelized and the overall test execution time reduced

Signed-off-by: Lars Asplund <lars.anders.asplund@gmail.com>
2 years ago
Lars Asplund 08c0c4c1b4 Make core testbenches recognized by VUnit
This commit also removes the dependencies these testbenches have on VHPIDIRECT.
The use of VHPIDIRECT limits the number of available simulators for the project. Rather than using
foreign functions the testbenches can be implemented entirely in VHDL where equivalent functionality exists.
For these testbenches the VHPIDIRECT-based randomization functions were replaced with VHDL-based functions.

The testbenches recognized by VUnit can be executed in parallel threads for better simulation performance using
the -p option to the run.py script

Signed-off-by: Lars Asplund <lars.anders.asplund@gmail.com>
2 years ago
Paul Mackerras 535341961d multiplier: Generalize interface to the multiplier
This makes the interface to the multiplier more general so an instance
of it can be used in the FPU.  It now has a 128-bit addend that is
added on to the product.  Instead of an input to negate the output,
it now has a "not_result" input to complement the output.  Execute1
uses not_result=1 and addend=-1 to get the effect of negating the
output.  The interface is defined this way because this is what can
be done easily with the Xilinx DSP slices in xilinx-mult.vhdl.

This also adds clock enable signals to the DSP slices, mostly for the
sake of reducing power consumption.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
3 years ago
Paul Mackerras 9880fc7435 multiply: Move selection of result bits into execute1
This puts the logic that selects which bits of the multiplier result
get written into the destination GPR into execute1, moved out from
multiply.

The multiplier is now expected to do an unsigned multiplication of
64-bit operands, optionally negate the result, detect 32-bit
or 64-bit signed overflow of the result, and return a full 128-bit
result.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
3 years ago
Anton Blanchard ab86b58d95 Exit cleanly from testbench on success
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
3 years ago
Paul Mackerras c9a2076dd3 execute1: Remember dest GPR, RC, OE, XER for slow operations
For multiply and divide operations, execute1 now records the
destination GPR number, RC and OE from the instruction, and the
XER value.  This means that the multiply and divide units don't
need to record those values and then send them back to execute1.
This makes the interface to those units a bit simpler.  They
simply report an overflow signal along with the result value, and
execute1 takes care of updating XER if necessary.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
3 years ago
Paul Mackerras 2167186b5f Make multiplier hang off the side of execute1
With this, the multiplier isn't a separate pipe that decode2 issues
instructions to, but rather is a unit that execute1 sends operands
to and which sends the result back to execute1, which then sends it
to writeback.  Execute1 now sends a stall signal when it gets a
multiply instruction until it gets a valid signal back from the
multiplier.

This all means that we no longer need to mark the multiply
instructions as single-issue.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
3 years ago
Paul Mackerras 374f4c536d writeback: Do data formatting and condition recording in writeback
This adds code to writeback to format data and test the result
against zero for the purpose of setting CR0.  The data formatter
is able to shift and mask by bytes and do byte reversal and sign
extension.  It can also put together bytes from two input
doublewords to support unaligned loads (including unaligned
byte-reversed loads).

The data formatter starts with an 8:1 multiplexer that is able
to direct any byte of the input to any byte of the output.  This
lets us rotate the data and simultaneously byte-reverse it.
The rotated/reversed data goes to a register for the unaligned
cases that overlap two doublewords.  Then there is per-byte logic
that does trimming, sign extension, and splicing together bytes
from a previous input doubleword (stored in data_latched) and the
current doubleword.  Finally the 64-bit result is tested to set
CR0 if rc = 1.

This removes the RC logic from the execute2, multiply and divide
units, and the shift/mask/byte-reverse/sign-extend logic from
loadstore2.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
4 years ago
Anton Blanchard 28e6d343dc Reformat multiply_tb
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
4 years ago
Anton Blanchard 1b6eef2a5d Fix multiply_tb
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
4 years ago
Anton Blanchard 5a29cb4699 Initial import of microwatt
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
4 years ago