From 01ee6d3e1de75a1aa08afd06f4dafe49d099e77e Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Wed, 29 Sep 2021 20:32:00 +0200
Subject: cc: work on a working if

---
 miniany/cc.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 107 insertions(+), 9 deletions(-)

(limited to 'miniany/cc.c')

diff --git a/miniany/cc.c b/miniany/cc.c
index 01472c9..c814f3d 100644
--- a/miniany/cc.c
+++ b/miniany/cc.c
@@ -15,6 +15,8 @@ enum {
 	S_SEMICOLON,
 	S_LPAREN,
 	S_RPAREN,
+	S_LBRACE,
+	S_RBRACE,
 	S_ASSIGN,
 	S_EQUALS,
 	S_NOT_EQUALS,
@@ -22,10 +24,12 @@ enum {
 	S_LESS_OR_EQUALS,
 	S_MORE,
 	S_MORE_OR_EQUALS,
-	S_INT = 10,
+	S_INT = 50,
+	S_IF,
+	S_ELSE,
 	S_PUTINT,
-	S_IDENT = 20,
-	S_NUM = 30,
+	S_IDENT = 60,
+	S_NUM = 70,
 	S_EOI = 98,
 	S_ERR = 99
 };
@@ -157,8 +161,18 @@ void scanIdent( struct Scanner *scanner )
 int keyword( char *ident )
 {
 	switch( ident[0] ) {
+		case 'e':
+			if( strcmp( ident, "else" ) == 0 ) {
+				return S_ELSE;
+			} else {
+				return 0;
+			}
+			break;
+			
 		case 'i':
-			if( strcmp( ident, "int" ) == 0 ) {
+			if( strcmp( ident, "if" ) == 0 ) {
+				return S_IF;
+			} else if( strcmp( ident, "int" ) == 0 ) {
 				return S_INT;
 			} else {
 				return 0;
@@ -260,6 +274,12 @@ int getToken( struct Scanner *scanner )
 		case ')':
 			scanner->token = S_RPAREN;
 			break;
+		case '{':
+			scanner->token = S_LBRACE;
+			break;
+		case '}':
+			scanner->token = S_RBRACE;
+			break;
 		case '0': case '1': case '2': case '3': case '4':
 		case '5': case '6': case '7': case '8': case '9':
 			scanNumber( scanner );
@@ -330,6 +350,7 @@ void freeSymbol( struct Symbol *sym )
 struct Scope {
 	char *name;
 	struct Symbol *sym;
+	int labelNo;
 };
 
 struct Scope *createScope( char *name )
@@ -339,6 +360,7 @@ struct Scope *createScope( char *name )
 	scope = (struct Scope *)malloc( sizeof( struct Scope ) );
 	scope->name = strdup( name );
 	scope->sym = NULL;
+	scope->labelNo = 0;
 	
 	return scope;
 }
@@ -1132,7 +1154,7 @@ struct ASTnode *parseExpression( struct Parser *parser, int level )
 		parser->token = getToken( parser->scanner );
 		right = parseExpression( parser, parserOperatorPrecedence( parser, op ) );
 		left = createASTbinary( op, left, right );
-		if( parser->token == S_EOI || parser->token == S_SEMICOLON ) {
+		if( parser->token == S_EOI || parser->token == S_SEMICOLON || parser->token == S_RPAREN ) {
 			return left;
                 }
 		op = parserTokenToOperator( parser, parser->token );
@@ -1209,6 +1231,70 @@ void parsePutint( struct Compiler *compiler )
 	freeASTnode( node );
 }
 
+/* TODO c4: forward reference of function */
+void parseStatementBlock( struct Compiler *compiler );
+
+char *genGetLabel( struct Compiler *compiler, struct Scope *scope )
+{
+	char *label;
+	char *s;
+	
+	label = (char *)malloc( MAX_IDENT_LEN );
+	strlcpy( label, "__", MAX_IDENT_LEN );
+	strlcat( label, scope->name, MAX_IDENT_LEN );
+	strlcat( label, "_", 1 );
+	s = (char *)malloc( MAX_IDENT_LEN );
+	itoa( scope->labelNo, s, 10 );
+	strlcat( label, s, MAX_IDENT_LEN );
+	free( (char *)s );
+	scope->labelNo++;
+	
+	return label;
+}
+
+void parseIf( struct Compiler *compiler )
+{
+	struct Parser *parser;
+	struct ASTnode *node;
+	char *label1, *label2;
+	
+	parser = compiler->parser;
+	parserExpect( parser, S_IF, "if" );
+	parserExpect( parser, S_LPAREN, "(" );
+	node = parseExpression( parser, 0 );
+	if( compiler->generator->debug ) {
+		putstring( "; if <cond> then" ); putnl( );
+	}
+	generateFromAST( compiler->generator, node, NOREG );
+	/* TODO: this should be condensed and optimized for the normal path
+	 *       (rare ifs, invert the condition, jmpXX directly */
+	putstring( "cmp al, 0" ); putnl( );
+	label1 = genGetLabel( compiler, compiler->parser->global_scope );
+	putstring( "je " ); putstring( label1 ); putnl( );
+	genFreeAllRegs( compiler->generator );
+	parserExpect( parser, S_RPAREN, ")" );
+	parseStatementBlock( compiler );
+	if( parser->token == S_ELSE ) {
+		label2 = genGetLabel( compiler, compiler->parser->global_scope );
+		putstring( "jmp " ); putstring( label2 ); putnl( );
+		if( compiler->generator->debug ) {
+			putstring( "; else" ); putnl( );
+		}
+		putstring( label1 ); putchar( ':' ); putnl( );
+		compiler->parser->token = getToken( compiler->parser->scanner );
+		parseStatementBlock( compiler );
+		putstring( label2 ); putchar( ':' ); putnl( );
+		free( label2 );
+	} else {
+		putstring( label1 ); putchar( ':' ); putnl( );
+	}
+		
+	if( compiler->generator->debug ) {
+		putstring( "; fi" ); putnl( );
+	}
+	free( label1 );
+}
+
 void parseStatement( struct Compiler *compiler )
 {
 	struct Parser *parser;
@@ -1220,7 +1306,9 @@ void parseStatement( struct Compiler *compiler )
 		parseAssignment( compiler );
 	} else if( parser->token == S_PUTINT ) {
 		parsePutint( compiler );
-	} else if( parser->token == S_EOI ) {
+	} else if( parser->token == S_IF ) {
+		parseIf( compiler );
+	} else if( parser->token == S_RBRACE || parser->token == S_EOI ) {
 		return;
 	} else {
 		scannerPrintErrorHeader( parser->scanner );
@@ -1232,6 +1320,18 @@ void parseStatement( struct Compiler *compiler )
 	}
 }
 
+void parseStatementBlock( struct Compiler *compiler )
+{
+	struct Parser *parser;
+	
+	parser = compiler->parser;
+	parserExpect( parser, S_LBRACE, "{" );
+	while( parser->token != S_RBRACE && parser->token != S_EOI ) {
+		parseStatement( compiler );
+	}	
+	parserExpect( parser, S_RBRACE, "}" );
+}
+
 /* compiler */
 
 struct Compiler *createCompiler( )
@@ -1263,9 +1363,7 @@ int main( int argc, char **argv )
 	/* compiler->generator->debug = 1; */
 	genPrologue( compiler );
 	compiler->parser->token = getToken( compiler->parser->scanner );
-	while( compiler->parser->token != S_EOI ) {
-		parseStatement( compiler );
-	}
+	parseStatementBlock( compiler );
 	genEpilogue( compiler );
 	freeCompiler( compiler );
 	
-- 
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