Unpacked array dimensions that are specified with only a single size value
(C-style unpacked arrays) have a $left of 0 and a $right of size - 1. E.g.
`x[10]` is equivalent to `x[0:9]`. This is defined in the LRM (1800-2017)
section 7.4.2 ("Unpacked arrays").
Currently it is implemented the other way around. There are a few contexts
where this distinction matters. For example array to array assignments,
which are supposed to be done left-to-right.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Dynamic arrays and queues can be implicitly cast between each other. At the
moment this only works if the right hand side is a signal or assignment
pattern.
But this should be possible for other r-value expression that returns a
queue or dynamic array type. E.g. function calls or class properties.
Since the expr_type() method is defined for all NetExpr objects we can use
that and do not have to cast to NetESignal.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Parameters can have string type and do the usual string stuff,
and also implement some of the string methods on string parameters
so that they evaluate down to constants.
Use the common data_type_or_implicit rules to support type
definitions for parameters. This eliminates a bunch of special
rules in parse.y, and opens the door for parameters having
more complex types.
As reported on iverilog-devel on 2018-10-12, a dimension size of zero
could case the compiler to go into an infinite loop. Further tests
showed that unsized or queue dimensions entered as packed dimensions
would cause the compiler to crash.
As discussed on iverilog-devel (2018-03-09), the existing implementation
(using Icarus-specific vpi functions) only worked with assignments to
simple variables, and could not be easily modified to work more generally.
So use the new vvp instructions added in the previous two commits.
This does a better job of setting the intermediate expression types
and widths when calculating the canonical index into a packed array.
It still doesn't properly handle out-of-bound indices (br953).
A compressed assignment statement should give exactly the same
result as the equivalent uncompressed statement. This means
that the type (signed/unsigned) of the LHS affects the type of
the RHS expression (unlike in normal assignments). We need to
take care that bit/part selects and concatenations are correctly
identified as unsigned values, even in the cases where they
reduce to a single whole signal.
If an error is found whilst elaborating a range expression in a signal
declaration, create a dummy range and continue elaboration. This stops
the compiler reporting an error every time that signal is referenced.
If an expression contains a division, remainder, or right shift operation,
set the expression min_width to UINT_MAX to flag that the expression width
cannot be pruned. Using UINT_MAX ensures that the min_width won't change
as we continue to elaborate the expression.
When a mux (NetCondit) is only writing to a part of the output
vector (and using only a part of the inputs) then blend the mux
output with the previous statement output.
If both conditions of a NetCondit device assign to the same subset
of l-value bits, then generate a smaller NetMux device that only
switches the affected bits.
Unsized expressions can expand to extremely large widths. Usually this
is actually a mistake in the source code, but it can lead to the compiler
temporarily using extremely large amounts of memory, or in the worst
case, crashing. This adds a cap on the width of unsized expressions (by
default 65536 bits, but overridable by the user), and causes a warning
message to be output when the cap is reached.
Lars-Peter Clausen
Martin Whitaker
Cary R
Stephen Williams
Noah Moroze
Larry Doolittle
Maciej Suminski