The Verilog LRM specifies that it is legal to give constant part
selects that are beyond the bounds of the identifier being selected.
But elaboration was flagging that as an error. This patch changes it
to a warning, and handles the cases by generating 'bx bits as needed.
IEEE1364 has specific names for the various generations of Verilog that
are supported. Icarus Verilog should stick to those names for selection
the language feature set.
In the process, the extensions that were tied to the 2x generations
are pulled out out and given their own enable flags. The makes all the
feature control more regular and understandable.
In continuous assign expressions, the abs() operator can't easily be
burried in generic unary handling, so add the IVL_LPM_ABS type and
generate it as needed.
1364-2001 does not allow a replication count of zero, but
1364-2005 allows them when the replication is enclosed in
a concatenation with other valid bits. This patch adds
code to perform these checks for procedural expressions.
Because of the NetNet object must have a width greater
than zero a replication used in a continuous assignment
can never have a count of zero.
This patch fixes the elaboration of parameters in a continuous
assignment to only pad the constants to their defined width.
Previously they were padded to the l-value width which resulted
in a vvp runtime error. This appears to be because the width
for padding is the defined width, but the constant is printed
using its internal width which previously could be larger than
its defined width.
These constants are local nets so I added that flag as well.
Parameters with vector descriptions that are not zero based and
are used in net contexts should generate the properly ranged
temporary signals. This causes subsequent part selects to work
out properly.
Binary bit based operators were not padding arguments if they had
different widths. The reduction operators and ! were not correctly
evaluating their arguments in a self-determined context.
This patch only applies to the ternary operator when used in a
continuous assignment. It adds short circuiting when the expression
is a constant true or false. It does not optimize the special case of
a constant 'bx expression with constant T/F expressions.
If implicit nets are declared during elaboration, then the success
of binding during elaboration will depend on the order of the code
in the source file.
This patch reworks much of the ternary code to short circuit when
possible and supports real values better. It adds a blend operator
for real values that returns 0.0 when the values differ and the value
when they match. This deviates slightly from the standard which
specifies that the value for reals is always 0.0 when the conditional
is 'bx. There are also a couple bug fixes.
These fixes have not been ported to continuous assignments yet.
Ternary operators used at compile time and in procedural assignments
should be complete (short circuit and support real values).
This patch adds support for delaying constants at time zero. It also
cleans up the code in elab_net.cc to use this capability instead of
building it with an extra BUFZ to carry the delay information.
This patch adds the power operator for signed bit based values
in a continuous assignment. It also fixes a few other power
expression width problems. The expression width is still not
calculated correctly, since the correct method can produce huge
possible bit widths. The result is currently limited to the width
of the native long. This is because lround() is used to convert
from a double to an integer. A check in the code generator protects
the runtime from this limitation.
This patch adds the power operator for unsigned bit based values
in a continuous assignment. It also refactors the power code for
normal expressions and continuous assignments.
This patch adds some checks to verify that shifts, the reduction
operators and the bit wise operators are not used with real values.
It also includes a few other cleanups.
This patch add delays in continuous assignments for the shift operators,
concatenations and replications. It also reports an error if the user
attempts to take the modulus of a real value.
This patch uncovers a couple other problems in the system. I am trying
to fix one of them. I will report the other problem shortly.
This patch fixes some of the delays in bit based continuous
assignments (unary -, unary +constants, string constants,
reduction operators and user functions).
Use draw_lpm_output_delay() in all functions that need it.
Addresses pr1879226 on a couple of levels. Analysis:
NetNet* PEBinary::elaborate_net_shift_() didn't flag dist==lwidth
as a case where all bits of the input are shifted away, which made
it create a real concatenator for this case. It attempted to create
NetNet*tmp with zero width, which doesn't work; (lsb,msb) ends up
as (0,-1), which is later interpreted as a 2-bit wide net.
Added an assert to the NetNet constructor to catch any other lurking
attempts to create zero-width nets.
Added short-circuit code to handle the case where all bits of the input
are shifted away. This case used to be "handled" by an assert failure.
Allow user defined functions to take real value arguments and return
real value results in net contexts. Use the data type of the nets
attached to the ports to define the data types of the arguments and
return value.
Previously only the logical operators (~, &, |, ^, etc.) supported a
delayed value in a continuous assignment. This patch should extend this
to all operators. An extensive check of real values was done. The same
will be done shortly for bit based nets.
Checks for constructs currently unsupported in continuous assignments
provide a more explicit message (** operator, real user functions,
{!, && and ||} operators with a real argument).
The continuous assignment multiply expands vectors to the sum
of the two widths. This is correct for bit based vectors, but
for real variables it should always be one bit wide.
System functions used in a continuous assignment must be defined
in the system function table since the name of the system functions
is kept in this definition. The default name is NULL which causes
problems. This patch add $rtoi to the system table and adds a check
for a NULL name.
In nets, if system functions return a real value the function lookup
was getting the correct width, but was also setting the width to 0,
which confused down-stream net handling. Real-value system fuctions
have a width of 1. (1 real-valued scalar.)
Rework the handling of file names to use a perm_string heap to hold
the file names, instead of the custom file name heap in the lexor.
Also rename the get_line to get_fileline to reflect its real duties.
This latter chage touched a lot of files.
Here are some more array fixes. They are mostly better error messages
instead of just asserting and some code cleanup. The one new thing
that probably should have been a separate submission is that down
indexed part select [base -: width] can now be a lvalue.
This patch fixes/enhances the array part select code. It also
verifies that any lval array index in a continuous assignment
is a constant value. Also, %set/av now uses index register 1 as
described in the documentation (as a bit offset).
Factor common code for processing signed constants to be padded.
In the process, fix some minor bugs in the padding decisions.
Signed-off-by: Stephen Williams <steve@icarus.com>
Non-constant indexed part select in continuous assignment generates
a select node with the correct width. In the process factor out and
share some of the part select calculations with expr part select
handling methods.
Signed-off-by: Stephen Williams <steve@icarus.com>
Cary R
Stephen Williams
Larry Doolittle
steve