From c3c7f10a4f6b55abbc5e577930ed59d94577cb59 Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Thu, 23 Jul 2020 15:53:46 +0200
Subject: asm-i386: started to work on const expressions, works again for pure
 integer/hex constants

---
 ecomp-c/asm-i386.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 127 insertions(+), 3 deletions(-)

diff --git a/ecomp-c/asm-i386.c b/ecomp-c/asm-i386.c
index fc91130..3cb6ff1 100644
--- a/ecomp-c/asm-i386.c
+++ b/ecomp-c/asm-i386.c
@@ -90,6 +90,8 @@ typedef enum {
 	S_rbrak,
 	S_plus,
 	S_minus,
+	S_star,
+	S_slash,
 	S_eof
 } S_Symbol;
 
@@ -108,6 +110,8 @@ static char *symname[S_eof+1] = {
 	"]",
 	"+",
 	"-",
+	"*",
+	"/",
 	"eof"
 };
 
@@ -395,6 +399,12 @@ static S_Symbol getSym( void )
 		case '+':
 			s = S_plus;
 			break;
+		case '*':
+			s = S_star;
+			break;
+		case '/':
+			s = S_slash;
+			break;
 		case 'f':
 			identifier( );
 			if( strcmp( ident, "format" ) == 0 ) {
@@ -761,6 +771,7 @@ typedef struct OperandInfo {
 	int addr;
 	Symbol *symbol;
 	struct OperandInfo *next;
+	struct ExpressionNode *node;
 } OperandInfo;
 
 typedef struct OpcodeInfo {
@@ -997,6 +1008,116 @@ static void assign_label( OperandInfo *operand_info, char *label )
 	}		
 }
 
+typedef enum ExpressionNodeType {
+	EXPRESSION_NODE_TYPE_CONST,
+	EXPRESSION_NODE_TYPE_VAR,
+	EXPRESSION_NODE_TYPE_OP
+} ExpressionNodeType;
+
+typedef struct ExpressionNode {
+	ExpressionNodeType type;
+	S_Symbol op;
+	struct ExpressionNode *left, *right;
+	int integer_value;
+	Symbol *symbol;
+} ExpressionNode;
+
+static ExpressionNode *create_expression_node( void )
+{
+	ExpressionNode *node = Allocate( sizeof( ExpressionNode ) );
+	node->left = NULL;
+	node->right = NULL;
+	
+	return node;
+}
+
+static void free_expression_node( ExpressionNode *node )
+{
+	if( node->left != NULL ) {
+		free_expression_node( node->left );
+	}
+	if( node->right != NULL ) {
+		free_expression_node( node->right );
+	}
+	free( node );
+}
+
+static ExpressionNode *parseFactor( void )
+{
+	Symbol *symbol;
+	ExpressionNode *node = NULL;
+
+	if( sym == S_number ) {
+		node = create_expression_node( );
+		node->type = EXPRESSION_NODE_TYPE_CONST;
+		node->integer_value = num;
+		sym = getSym( );
+	} else if( sym == S_ident ) {
+		symbol = get_symbol( ident );
+		if( symbol == NULL ) {
+			Abort( "Unknown identifier '%s'", ident );
+		}	
+		node = create_expression_node( );
+		node->type = EXPRESSION_NODE_TYPE_VAR;
+		node->symbol = symbol;
+		sym = getSym( );			
+	} else {
+		Abort( "Expected a literal, a variable or a constant." );
+	}
+	
+	return node;
+}
+
+static ExpressionNode *parseTerm( void )
+{
+	ExpressionNode *node, *tmp;
+	
+	node = parseFactor( );
+
+	while( sym == S_star || sym == S_slash ) {
+		tmp = node;
+		node = create_expression_node( );
+		node->type = EXPRESSION_NODE_TYPE_OP;
+		node->op = sym;
+		sym = getSym( );
+		node->left = tmp;
+		node->right = parseFactor( );
+	}
+	
+	return node;
+}
+
+static ExpressionNode *parseExpression( void )
+{
+	ExpressionNode *node, *tmp;
+	
+	node = parseTerm( );
+	while( sym == S_plus || sym == S_minus ) {
+		tmp = node;
+		node = create_expression_node( );
+		node->type = EXPRESSION_NODE_TYPE_OP;
+		node->op = sym;
+		sym = getSym( );
+		node->left = tmp;
+		node->right = parseTerm( );
+	}
+	
+	return node;
+}
+
+static int evaluate_const_expression_as_integer( ExpressionNode *node )
+{
+	switch( node->type ) {
+		case EXPRESSION_NODE_TYPE_CONST:
+			return node->integer_value;
+		case EXPRESSION_NODE_TYPE_VAR:
+		case EXPRESSION_NODE_TYPE_OP:
+			Abort( "Const node expression node not implemented yet" );
+	}
+	
+	return 0;
+}
+
 static OperandInfo *parseOperand( OpcodeInfo *opcode_info )
 {
 	OperandInfo *operand_info;
@@ -1018,10 +1139,13 @@ static OperandInfo *parseOperand( OpcodeInfo *opcode_info )
 		}
 		sym = getSym( );
 	} else if( sym == S_number ) {
-		/* absolute operand, like in mov eax, $1 */
+		/* absolute operand, like in mov eax, $1,
+		 * we have assemble-time expressions here
+		 */
 		operand_info->type = OPERAND_ABSOLUTE;
-		operand_info->num = num;
-		sym = getSym( );
+		operand_info->node = parseExpression( );
+		operand_info->num = evaluate_const_expression_as_integer( operand_info->node );
+		free_expression_node( operand_info->node );
 	} else if( sym == S_string ) {
 		operand_info->type = OPERAND_ABSOLUTE;
 		operand_info->str = AllocateAndCopyStr( str );
-- 
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