[Iverilog-devel] Left shift of unsized constant

[Stephen W. <st...@ic...>]

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Cary R. wrote:
| It appears that the writemem* problems are created by the
1<<(6-count). It look like the 1 is being interpreted as a two bit wide
value instead of the normal integer 32 bits. This means that for values
of count less than five the result is zero. The following simple program
is producing incorrect results:
|
| module main;
|   reg [2:0] val;
|
|   initial begin
|     for (val=0; val<=6; val=val+1) begin
|       $displayh(val,, 1<<(6-val));
|     end
|   end
| endmodule

Hmm, ideally, I would like the left shift in a self-determined
context like this to take on the size of the largest possible
value that it can emit, but I think that can lead to crazyness.
For example, if val were an integer (32bits) then the width of
the shift expression would be 2**32. NAK!

So I'm thinking that for left shift, if the left side is an
unsized constant and the right side is non-consant, then it
should take on the size of the integer. If both sides are
constant, then it should take on exactly the right size. Does
that sound workable to you?

- --
Steve Williams                "The woods are lovely, dark and deep.
steve at icarus.com           But I have promises to keep,
http://www.icarus.com         and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."
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