[Zamiacad-devel] issues in 'mux' IG

[Saif A. <sye...@gm...>]

hello Guenter,
as part of the VHDL-to-SC conversion, I was looking at the GCD-2 code.
there is a description of a mux as follows:

entity mux is
    port(	rst, sLine: in std_logic;
		load, result: in std_logic_vector( 3 downto 0 );
		output: out std_logic_vector( 3 downto 0 )
    );
end mux;
architecture mux_arc of mux is
begin
    process( rst, sLine, load, result )
    begin
	if( rst = '1' ) then
	    output <= "0000";		-- do nothing
	elsif sLine = '0' then
	    output <= load;		-- load inputs
	else
	    output <= result;		-- load results
	end if;
    end process;
end mux_arc;

there are few doubts that need clarifications:
1. in this mux description, the last assignment operation (output <=
result;) is
the 'else' clause of the second if-statement (if sLine = '0').
Correct?

2. in the IG graph, the second if-statement (if sLine = '0') and the
last assignment operation (output <= result;)
both are coming within the first 'else' statement.
logically, this renders the code as:
	IF ( rst = '1' ) then
	    output <= "0000";
	ELSE
	    IF sLine = '0' then output <= load;
	        ELSE nothing;
	        END-IF
	    output <= result; //this line will always be executed within this 'else'
	END-IF

I am copying below the DOT code starting from the first if-statement
(rst = '1').
Please clarify if I am mis-interpreting something in this context.

thanks,
Saif


o4763369[shape=none,margin=0,label=<
<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
<TR><TD COLSPAN="2">org.zamia.instgraph.IGSequentialIf</TD></TR>
 <TR><TD>fThenSOS</TD><TD PORT="p0">obj</TD></TR>
 <TR><TD>fElseSOS</TD><TD PORT="p1">obj</TD></TR>      <==============
the Else-SOS resolves to 2 statements
 <TR><TD>fCond</TD><TD PORT="p2">obj</TD></TR>
 <TR><TD>fId</TD><TD PORT="p3">null</TD></TR>
  </TABLE>>];
  o4763369:p0 -> o22716491;
  o4763369:p1 -> o13745259;
  o4763369:p2 -> o29275392;


o13745259[shape=none,margin=0,label=<
<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
<TR><TD COLSPAN="2">org.zamia.instgraph.IGSequenceOfStatements</TD></TR>
 <TR><TD>fStmts</TD><TD PORT="p0">obj</TD></TR>
 <TR><TD>fId</TD><TD PORT="p1">null</TD></TR>
  </TABLE>>];
  o13745259:p0 -> o391089378;

  o391089378[shape=none,margin=0,label=<
<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
<TR><TD COLSPAN="2">java.util.ArrayList</TD></TR>
 <TR><TD>size</TD><TD PORT="p0">2</TD></TR>
  </TABLE>>];
  o391089378:p0 -> o12115416;
  o391089378:p0 -> o15510521;

    o12115416[shape=none,margin=0,label=<
<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
<TR><TD COLSPAN="2">org.zamia.instgraph.IGSequentialIf</TD></TR>
 <TR><TD>fThenSOS</TD><TD PORT="p0">obj</TD></TR>
 <TR><TD>fElseSOS</TD><TD PORT="p1">null</TD></TR>
<================= there is no statement in the 'else'
 <TR><TD>fCond</TD><TD PORT="p2">obj</TD></TR>
 <TR><TD>fId</TD><TD PORT="p3">null</TD></TR>
  </TABLE>>];
  o12115416:p0 -> o27869524;
  o12115416:p2 -> o25931923;


o15510521[shape=none,margin=0,label=<
<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
<TR><TD COLSPAN="2">org.zamia.instgraph.IGSequentialAssignment</TD></TR>
 <TR><TD>fValue</TD><TD PORT="p0">obj</TD></TR>
 <TR><TD>fTarget</TD><TD PORT="p1">obj</TD></TR>
 <TR><TD>fId</TD><TD PORT="p2">null</TD></TR>
  </TABLE>>];
  o15510521:p0 -> o948824;
  o15510521:p1 -> o8542380;