[SOLVED] PNFHA: if-else code generation

des_a · 09-10-2014, 11:23 PM

complicatediftest3:

Code:

if (3 + 2)
{
 ;
}
else if (false)
{
 ;
}
else
 ;

compiles to:

Code:

VERSION TVOID 0V


; Begin if :1
ALOAD TBOOLEAN true
CGOTOL TSTRING "if_part_1"
GOTOL TSTRING "else_part_or_end_1"


LBL TSTRING "if_part_1"
VOID TVOID 0V
; End if code :1
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_1"
; Begin if :2
ALOAD TBOOLEAN false
CGOTOL TSTRING "if_part_2"
GOTOL TSTRING "else_part_or_end_2"


LBL TSTRING "if_part_2"
VOID TVOID 0V
; End if code :2
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_2"
VOID TVOID 0V
; End if or else code :2
GOTOL TSTRING "end"


LBL TSTRING "end"
; End if :2
; End if or else code :1
GOTOL TSTRING "end"


LBL TSTRING "end"
; End if :1

END TVOID 0V

and should compile to:

Code:

VERSION TVOID 0V


; Begin if :1
ALOAD TBOOLEAN true
CGOTOL TSTRING "if_part_1"
GOTOL TSTRING "else_part_or_end_1"


LBL TSTRING "if_part_1"
VOID TVOID 0V
; End if code :1
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_1"
; Begin if :2
ALOAD TBOOLEAN false
CGOTOL TSTRING "if_part_2"
GOTOL TSTRING "else_part_or_end_2"


LBL TSTRING "if_part_2"
VOID TVOID 0V
; End if code :2
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_2"
VOID TVOID 0V
; End if or else code :2
GOTOL TSTRING "end"


LBL TSTRING "end"
; End if :2
; End if or else code :1
GOTOL TSTRING "end1"


LBL TSTRING "end1"
; End if :1

END TVOID 0V

des_a · 09-10-2014, 11:43 PM

Finally, complicatediftest4:

Code:

if (3 + 2)
{
 ;
}
else if (false)
{
 ;
}
else if (true)
{
 ;
}
else
 ;

compiles to:

Code:

VERSION TVOID 0V


; Begin if :1
ALOAD TBOOLEAN true
CGOTOL TSTRING "if_part_1"
GOTOL TSTRING "else_part_or_end_1"


LBL TSTRING "if_part_1"
VOID TVOID 0V
; End if code :1
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_1"
; Begin if :2
ALOAD TBOOLEAN false
CGOTOL TSTRING "if_part_2"
GOTOL TSTRING "else_part_or_end_2"


LBL TSTRING "if_part_2"
VOID TVOID 0V
; End if code :2
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_2"
; Begin if :3
ALOAD TBOOLEAN true
CGOTOL TSTRING "if_part_3"
GOTOL TSTRING "else_part_or_end_3"


LBL TSTRING "if_part_3"
VOID TVOID 0V
; End if code :3
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_3"
VOID TVOID 0V
; End if or else code :3
GOTOL TSTRING "end"


LBL TSTRING "end"
; End if :3
; End if or else code :2
GOTOL TSTRING "end"


LBL TSTRING "end"
; End if :2
; End if or else code :1
GOTOL TSTRING "end"


LBL TSTRING "end"
; End if :1

END TVOID 0V

but should compile to:

Code:

VERSION TVOID 0V


; Begin if :1
ALOAD TBOOLEAN true
CGOTOL TSTRING "if_part_1"
GOTOL TSTRING "else_part_or_end_1"


LBL TSTRING "if_part_1"
VOID TVOID 0V
; End if code :1
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_1"
; Begin if :2
ALOAD TBOOLEAN false
CGOTOL TSTRING "if_part_2"
GOTOL TSTRING "else_part_or_end_2"


LBL TSTRING "if_part_2"
VOID TVOID 0V
; End if code :2
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_2"
; Begin if :3
ALOAD TBOOLEAN true
CGOTOL TSTRING "if_part_3"
GOTOL TSTRING "else_part_or_end_3"


LBL TSTRING "if_part_3"
VOID TVOID 0V
; End if code :3
GOTOL TSTRING "end"


LBL TSTRING "else_part_or_end_3"
VOID TVOID 0V
; End if or else code :3
GOTOL TSTRING "end"


LBL TSTRING "end1"
; End if :3
; End if or else code :2
GOTOL TSTRING "end"


LBL TSTRING "end2"
; End if :2
; End if or else code :1
GOTOL TSTRING "end"


LBL TSTRING "end"
; End if :1

END TVOID 0V

des_a · 09-10-2014, 11:45 PM

What is an algorithm to fix up these (and any other) if-else statement so it turns out how it's supposed to?

des_a · 09-10-2014, 11:50 PM

Or is this too complicated to solve, because something in my AST needs to be adjusted?

des_a · 09-13-2014, 01:11 AM

My problems with code generation seem to be caused by the optional else clause. The desire is to have this function as it does in C++, but if I can't make that work, maybe there is a better way to do it. I could omit the optional else, but it still has to have a construct for being able to write code such as the if-else ladder. I seem to be having trouble, because the code for the if-else ladder is complicated.

NevemTeve · 09-14-2014, 12:14 AM

For a start, stop using label "end", instead use labels like "iftrue_N", "iffalse_N" and "endif_N". (N is the 'ifcounter')

Also, you could remove word "TSTRING" from your code, it is of no use.

des_a · 09-17-2014, 12:07 AM

I could try using labels like that. TSTRING is the type for the instruction and is needed. I "could" make an even higher level language, but that is mostly an assembly type language, and remove it in that and do some modifications to the language, but it is needed in the actual runnable language, and therefore carries over to the assembly language. T stands for type, and STRING, is a string type. The LBL instruction takes either TVOID or TSTRING. TSTRING specifies a string type label, where you could jump to it with the string name, and TVOID simply specifies a label number type jump, where you do NOT have a name. Therefore with that kind of jump, you must use a label number. You can, use a label number to jump to a string type label, but you do not have to. Since I already had label number jumps, implementing it in this way made the language more powerful, rather than just allowing a string type jump. It also allowed backward compatibility for the code I'd already written, though it isn't much.

des_a · 09-17-2014, 12:14 AM

The reason by the way, that the lower levels need the TSTRING, and cannot be assuming it in certain cases, is because it makes the syntax simpler to understand to always have an instruction, a type, and an operand. Earlier languages which were steps to this version of the language (which is a fully working language, though maybe not fully developed), had sometimes just part of it. But I decided it's clearer to always have a type, even if the type ends up being TVOID (void value). In higher levels above the assembly language, it is okay to just have a string or a value, and let the computer figure out in the lower level which value to assign it, as long as it's also specified in a way in which the user will understand it too. But for the assembly language, and the lowest level language (PNF), it is not okay. Would it make it that much easier if I created such a high level language and compiled this language to that?

NevemTeve · 09-17-2014, 12:25 AM

TSTRING is not 'the type of the instruction', it is 'the type of the next operand':

eg:

Code:

CGOTOL TSTRING "if_part_2"

You could simply write this:

Code:

CGOTOL "if_part_2"

Lexical parsers do recognize string-literals without putting reserved word TSTRING before them.

des_a · 09-17-2014, 01:11 AM

That's what I meant. I know it could be done, but it would make the lower levels harder to understand. If I needed to do that, I would want a higher level language and compile to that instead.

des_a · 09-17-2014, 01:58 AM

Also, at the lowest level, 0 could be either a void value, false, the number 0, a null character, or a null string. It'd be tricky to tell which is meant. At the assembly level, where we use words instead of numbers, I could've had the assembler figure it out, but that would break it's ability to generate ANY code. Should I make a higher level that makes assembly nicer, and compile to that?

NevemTeve · 09-17-2014, 02:35 AM

No, right now you should read post #82.

des_a · 09-18-2014, 01:44 PM

So I changed my code to match the action layout of post #82. My code now looks like:

Code:

if_statement:		IF
			{
			 ASTNode if_statementp1("if_statementp1");

			 ++ifcounter;
			 ifgoto = ifcounter < 2 ? ifcounter : ifcounter + 1;

			 String if_body_str = "if_body_";
			 if_body_str += ifgoto - 1;

			 labelTable.insert();
			 labelTable[labelTable.length() - 1].name(if_body_str);
			 labelTable[labelTable.length() - 1].address(labelTable.length() - 2);

			 if_statementp1.conprint("; Begin if :%u\n", ifcounter);

			 tree.add_node(if_statementp1);		
			}
			LEFTP expression RIGHTP
			{
			 ASTNode if_statementp2("if_statementp2");


			 if_statementp2.conprint("ALOAD TBOOLEAN %s\n", $2.to_boolean().get().getString().c_str());
			 if_statementp2.conprint("CGOTOL TSTRING \"iftrue_%u\"\n", ifcounter);
			 if_statementp2.conprint("GOTOL TSTRING \"iffalse_or_end_%u\"\n", ifcounter);

			 if_statementp2.conprint("\n\nLBL TSTRING \"iftrue_%u\"\n", ifcounter);


			 tree.add_node(if_statementp2);
			}
			stmt
			{
			 ASTNode if_statementp3("if_statementp3");
			 // Code for if will be inserted here...
			 if_statementp3.conprint("; End if code :%u\n", ifcounter);
			 ifbegin = outcount;

			 String after_if_str = "after_if_";
 			 after_if_str += ifgoto - 1;

			 labelTable.insert();
			 labelTable[labelTable.length() - 1].name(after_if_str);
			 labelTable[labelTable.length() - 1].address(labelTable.length() - 2);
			 endifbegin = outcount - 1;

			 if_statementp3.conprint("GOTOL TSTRING \"end_%u\"\n", ifcounter);

			 tree.add_node(if_statementp3);
			}
			opt_else
			{
			 --ifcounter;
			 ++ifnest;
			}
			;

opt_else:		{
			 ASTNode if_statementp4("if_statementp4");
			 if_statementp4.conprint("\n\nLBL TSTRING \"iffalse_or_end_%u\"\n", ifcounter);
			 tree.add_node(if_statementp4);
			}
			| ELSE
			{
			 ASTNode if_statementp5("if_statementp5");

			 ++elsecounter;
			 
			 // Code for else will be inserted here if exists...
			 if_statementp5.conprint("; End if or else code :%u\n", ifcounter);
			 elsebegin = outcount;

			 String else_body_str = "else_body_";
			 else_body_str += ifcounter;
			 String after_if_str = "after_if_";
 			 after_if_str += ifgoto - 1;

			 labelTable.remove();

			 labelTable.insert();
			 labelTable[labelTable.length() - 1].name(else_body_str);
			 labelTable[labelTable.length() - 1].address(labelTable.length() - 2);

			 labelTable.insert();
			 labelTable[labelTable.length() - 1].name(after_if_str);
			 labelTable[labelTable.length() - 1].address(labelTable.length() - 2);

			 if_statementp5.conprint("GOTOL TSTRING \"end_%u\"\n", ifcounter);


			 tree.add_node(if_statementp5);
			}
			stmt
			{
			 ASTNode if_statementp6("if_statementp6");
			 if_statementp6.conprint("\n\nLBL TSTRING \"end_%u\"\n", ifcounter);
			 if_statementp6.conprint("; End if :%u\n", ifcounter);
			 tree.add_node(if_statementp6);
			}
			;

des_a · 09-18-2014, 01:46 PM

iftest, which looks like this:

Code:

;
if (3 + 2)
 ;
end 0;

Now compiles to:

Code:

VERSION TVOID 0V


VOID TVOID 0V
; Begin if :1
ALOAD TBOOLEAN false
CGOTOL TSTRING "iftrue_1"
GOTOL TSTRING "iffalse_or_end_1"


LBL TSTRING "iftrue_1"
VOID TVOID 0V
; End if code :1
GOTOL TSTRING "end_1"


LBL TSTRING "iffalse_or_end_1"
QUIT TVOID 0

END TVOID 0V

It should compile to:

Code:

VERSION TVOID 0V


VOID TVOID 0V
; Begin if :1
ALOAD TBOOLEAN false
CGOTOL TSTRING "iftrue_1"
GOTOL TSTRING "end_1"


LBL TSTRING "iftrue_1"
VOID TVOID 0V
; End if code :1
GOTOL TSTRING "end_1"


LBL TSTRING "end_1"
QUIT TVOID 0

END TVOID 0V

des_a · 09-18-2014, 01:51 PM

ifelsetest:

Code:

if (3 + 2)
 ;
else
 ;

compiles to:

Code:

VERSION TVOID 0V


; Begin if :1
ALOAD TBOOLEAN false
CGOTOL TSTRING "iftrue_1"
GOTOL TSTRING "iffalse_or_end_1"


LBL TSTRING "iftrue_1"
VOID TVOID 0V
; End if code :1
GOTOL TSTRING "end_1"
; End if or else code :1
GOTOL TSTRING "end_1"
VOID TVOID 0V


LBL TSTRING "end_1"
; End if :1

END TVOID 0V