parser enhancement to get rid of unneeded statements

lib/parse.c

@@ -994,6 +994,223 @@ oops:
 	return -1;
 }
 
+static int is_nde_bool_literal_atom (hawk_nde_t* nde)
+{
+	switch (nde->type)
+	{
+		case HAWK_NDE_XFALSE:
+		case HAWK_NDE_XTRUE:
+		case HAWK_NDE_XNIL:
+		case HAWK_NDE_INT:
+		case HAWK_NDE_FLT:
+		case HAWK_NDE_STR:
+		case HAWK_NDE_MBS:
+			return 1;
+		default:
+			return 0;
+	}
+}
+
+/* return the effective literal node for boolean decision.
+ * if nde is a grouped node, every grouped element must be literal.
+ * the returned node is the last literal element in the group.
+ *
+ * examples:
+ *   (1, 0)         -> INT(0)
+ *   ((1, 0))       -> INT(0)
+ *   ("x", @false)  -> XFALSE
+ *   (abc(), 0)     -> HAWK_NULL
+ */
+static hawk_nde_t* get_nde_bool_literal_tail (hawk_nde_t* nde, int depth)
+{
+	if (depth >= 256) return HAWK_NULL; /* i don't wawnt to support to deep recursion. TODO: remove hard-coded value or remove recursion? */
+
+	if (nde->type == HAWK_NDE_GRP)
+	{
+		hawk_nde_t* cur, * last;
+
+		cur = ((hawk_nde_grp_t*)nde)->body;
+		HAWK_ASSERT(cur != HAWK_NULL);
+
+		last = HAWK_NULL;
+		do
+		{
+			last = get_nde_bool_literal_tail(cur, depth + 1);
+			if (!last) return HAWK_NULL;
+			cur = cur->next;
+		}
+		while (cur);
+
+		return last;
+	}
+
+	return is_nde_bool_literal_atom(nde)? nde: HAWK_NULL;
+}
+
+static nde_hard_bool_t classify_nde_hard_bool (hawk_nde_t* nde)
+{
+	nde = get_nde_bool_literal_tail(nde, 0);
+	if (!nde) return NDE_HARD_BOOL_UNKNOWN;
+
+	switch (nde->type)
+	{
+		case HAWK_NDE_XFALSE:
+		case HAWK_NDE_XNIL:
+			return NDE_HARD_BOOL_FALSE;
+
+		case HAWK_NDE_XTRUE:
+			return NDE_HARD_BOOL_TRUE;
+
+		case HAWK_NDE_INT:
+			return (((hawk_nde_int_t*)nde)->val == 0)?
+				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
+
+		case HAWK_NDE_FLT:
+			return (((hawk_nde_flt_t*)nde)->val == 0.0)?
+				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
+
+		case HAWK_NDE_STR:
+			return (((hawk_nde_str_t*)nde)->len == 0)?
+				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
+
+		case HAWK_NDE_MBS:
+			return (((hawk_nde_mbs_t*)nde)->len == 0)?
+				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
+
+		default:
+			return NDE_HARD_BOOL_UNKNOWN;
+	}
+}
+
+static HAWK_INLINE int is_nde_hard_false (hawk_nde_t* nde)
+{
+	return classify_nde_hard_bool(nde) == NDE_HARD_BOOL_FALSE;
+}
+
+static HAWK_INLINE int is_nde_hard_true (hawk_nde_t* nde)
+{
+	return classify_nde_hard_bool(nde) == NDE_HARD_BOOL_TRUE;
+}
+
+static int is_nde_unconditional_terminator (hawk_nde_t* nde)
+{
+	switch (nde->type)
+	{
+		case HAWK_NDE_EXIT: /* exit or @abort */
+		case HAWK_NDE_RETURN: /* return */
+		case HAWK_NDE_NEXT:
+		case HAWK_NDE_NEXTFILE:
+			return 1;
+
+/* TODO: recursion depth check? */
+		case HAWK_NDE_BLK:
+		{
+			hawk_nde_t* p;
+			for (p = ((hawk_nde_blk_t*)nde)->body; p; p = p->next)
+			{
+				if (is_nde_unconditional_terminator(p)) return 1;
+			}
+			return 0;
+		}
+
+		case HAWK_NDE_IF:
+		{
+			hawk_nde_if_t* p = (hawk_nde_if_t*)nde;
+			return p->else_part &&
+			       is_nde_unconditional_terminator(p->else_part) &&
+			       is_nde_unconditional_terminator(p->then_part);
+		}
+
+		default:
+			return 0;
+	}
+}
+
+static int does_nde_have_side_effect (hawk_nde_t* nde)
+{
+	HAWK_ASSERT(nde != HAWK_NULL);
+
+	switch (nde->type)
+	{
+		case HAWK_NDE_NULL:
+		case HAWK_NDE_CHAR:
+		case HAWK_NDE_BCHR:
+		case HAWK_NDE_INT:
+		case HAWK_NDE_FLT:
+		case HAWK_NDE_STR:
+		case HAWK_NDE_MBS:
+		case HAWK_NDE_REX:
+		case HAWK_NDE_XNIL:
+		case HAWK_NDE_XTRUE:
+		case HAWK_NDE_XFALSE:
+		case HAWK_NDE_XARGC:
+		case HAWK_NDE_XARGV:
+		case HAWK_NDE_FUN:
+		case HAWK_NDE_MODSYM:
+		case HAWK_NDE_NAMED:
+		case HAWK_NDE_GBL:
+		case HAWK_NDE_LCL:
+		case HAWK_NDE_ARG:
+			return 0;
+
+		case HAWK_NDE_NAMEDIDX:
+		case HAWK_NDE_GBLIDX:
+		case HAWK_NDE_LCLIDX:
+		case HAWK_NDE_ARGIDX:
+			return does_nde_have_side_effect(((hawk_nde_var_t*)nde)->idx);
+
+		case HAWK_NDE_XARGVIDX:
+			return does_nde_have_side_effect(((hawk_nde_xargvidx_t*)nde)->pos);
+
+		case HAWK_NDE_POS:
+			return does_nde_have_side_effect(((hawk_nde_pos_t*)nde)->val);
+
+		case HAWK_NDE_GRP:
+		{
+			hawk_nde_t* p;
+			for (p = ((hawk_nde_grp_t*)nde)->body; p; p = p->next)
+			{
+				if (does_nde_have_side_effect(p)) return 1;
+			}
+			return 0;
+		}
+
+		case HAWK_NDE_EXP_BIN:
+			return does_nde_have_side_effect(((hawk_nde_exp_t*)nde)->left) ||
+			       does_nde_have_side_effect(((hawk_nde_exp_t*)nde)->right);
+
+		case HAWK_NDE_EXP_UNR:
+			return does_nde_have_side_effect(((hawk_nde_exp_t*)nde)->left);
+
+		case HAWK_NDE_BLK:
+		{
+			hawk_nde_t* p;
+			for (p = ((hawk_nde_blk_t*)nde)->body; p; p = p->next)
+			{
+				if (does_nde_have_side_effect(p)) return 1;
+			}
+			return 0;
+		}
+
+		case HAWK_NDE_CND:
+			return does_nde_have_side_effect(((hawk_nde_cnd_t*)nde)->test) ||
+			       does_nde_have_side_effect(((hawk_nde_cnd_t*)nde)->left) ||
+			       does_nde_have_side_effect(((hawk_nde_cnd_t*)nde)->right);
+
+		case HAWK_NDE_IF:
+		{
+			hawk_nde_if_t* p = (hawk_nde_if_t*)nde;
+			return does_nde_have_side_effect(p->test) ||
+			       does_nde_have_side_effect(p->then_part) ||
+			       (p->else_part && does_nde_have_side_effect(p->else_part));
+		}
+
+		/* all other nodes */
+		default:
+			return 1;
+	}
+}
+
 static int parse_progunit (hawk_t* hawk)
 {
 	/*
@@ -2024,6 +2241,7 @@ static hawk_nde_t* parse_block (hawk_t* hawk, const hawk_loc_t* xloc, int flags)
 	hawk_nde_blk_t* block;
 	hawk_oow_t nlcls_outer, nlcls_max, tmp;
 	nde_chain_t local_inits = { HAWK_NULL, HAWK_NULL };
+	int dead_code;
 
 	nlcls_outer = HAWK_ARR_SIZE(hawk->parse.lcls);
 	nlcls_max = hawk->parse.nlcls_max;
@@ -2034,6 +2252,7 @@ static hawk_nde_t* parse_block (hawk_t* hawk, const hawk_loc_t* xloc, int flags)
 	/* block body */
 	head = local_inits.head;
 	curr = local_inits.tail;
+	dead_code = 0;
 
 	while (1)
 	{
@@ -2100,9 +2319,17 @@ static hawk_nde_t* parse_block (hawk_t* hawk, const hawk_loc_t* xloc, int flags)
 				continue;
 			}
 
+			if (dead_code)
+			{
+				hawk_clrpt(hawk, nde);
+				continue;
+			}
+
 			if (curr == HAWK_NULL) head = nde;
 			else curr->next = nde;
 			curr = nde;
+
+			if (is_nde_unconditional_terminator(nde)) dead_code = 1;
 		}
 	}
 
@@ -3025,102 +3252,22 @@ oops:
 	return HAWK_NULL;
 }
 
-static int is_nde_bool_literal_atom (hawk_nde_t* nde)
+static hawk_nde_t* make_null_nde (hawk_t* hawk, const hawk_loc_t* xloc)
 {
-	switch (nde->type)
+	hawk_nde_t* null_nde;
+
+	null_nde = (hawk_nde_t*)hawk_callocmem(hawk, HAWK_SIZEOF(*null_nde));
+	if (HAWK_UNLIKELY(!null_nde))
 	{
-		case HAWK_NDE_XFALSE:
-		case HAWK_NDE_XTRUE:
-		case HAWK_NDE_XNIL:
-		case HAWK_NDE_INT:
-		case HAWK_NDE_FLT:
-		case HAWK_NDE_STR:
-		case HAWK_NDE_MBS:
-			return 1;
-		default:
-			return 0;
-	}
-}
-
-/* return the effective literal node for boolean decision.
- * if nde is a grouped node, every grouped element must be literal.
- * the returned node is the last literal element in the group.
- *
- * examples:
- *   (1, 0)         -> INT(0)
- *   ((1, 0))       -> INT(0)
- *   ("x", @false)  -> XFALSE
- *   (abc(), 0)     -> HAWK_NULL
- */
-static hawk_nde_t* get_nde_bool_literal_tail (hawk_nde_t* nde, int depth)
-{
-	if (depth >= 256) return HAWK_NULL; /* i don't wawnt to support to deep recursion. TODO: remove hard-coded value or remove recursion? */
-
-	if (nde->type == HAWK_NDE_GRP)
-	{
-		hawk_nde_t* cur, * last;
-
-		cur = ((hawk_nde_grp_t*)nde)->body;
-		HAWK_ASSERT(cur != HAWK_NULL);
-
-		last = HAWK_NULL;
-		do
-		{
-			last = get_nde_bool_literal_tail(cur, depth + 1);
-			if (!last) return HAWK_NULL;
-			cur = cur->next;
-		}
-		while (cur);
-
-		return last;
+		ADJERR_LOC(hawk, xloc);
+		return HAWK_NULL;
 	}
 
-	return is_nde_bool_literal_atom(nde)? nde: HAWK_NULL;
-}
+	null_nde->type = HAWK_NDE_NULL;
+	if (xloc) null_nde->loc = *xloc;
+	null_nde->next = HAWK_NULL;
 
-static nde_hard_bool_t classify_nde_hard_bool (hawk_nde_t* nde)
-{
-	nde = get_nde_bool_literal_tail(nde, 0);
-	if (!nde) return NDE_HARD_BOOL_UNKNOWN;
-
-	switch (nde->type)
-	{
-		case HAWK_NDE_XFALSE:
-		case HAWK_NDE_XNIL:
-			return NDE_HARD_BOOL_FALSE;
-
-		case HAWK_NDE_XTRUE:
-			return NDE_HARD_BOOL_TRUE;
-
-		case HAWK_NDE_INT:
-			return (((hawk_nde_int_t*)nde)->val == 0)?
-				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
-
-		case HAWK_NDE_FLT:
-			return (((hawk_nde_flt_t*)nde)->val == 0.0)?
-				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
-
-		case HAWK_NDE_STR:
-			return (((hawk_nde_str_t*)nde)->len == 0)?
-				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
-
-		case HAWK_NDE_MBS:
-			return (((hawk_nde_mbs_t*)nde)->len == 0)?
-				NDE_HARD_BOOL_FALSE: NDE_HARD_BOOL_TRUE;
-
-		default:
-			return NDE_HARD_BOOL_UNKNOWN;
-	}
-}
-
-static HAWK_INLINE int is_nde_hard_false (hawk_nde_t* nde)
-{
-	return classify_nde_hard_bool(nde) == NDE_HARD_BOOL_FALSE;
-}
-
-static HAWK_INLINE int is_nde_hard_true (hawk_nde_t* nde)
-{
-	return classify_nde_hard_bool(nde) == NDE_HARD_BOOL_TRUE;
+	return null_nde;
 }
 
 static hawk_nde_t* parse_if (hawk_t* hawk, const hawk_loc_t* xloc)
@@ -3148,10 +3295,6 @@ static hawk_nde_t* parse_if (hawk_t* hawk, const hawk_loc_t* xloc)
 		goto oops;
 	}
 
-/* TODO: optimization. if you know 'test' evaluates to true or false,
- *       you can drop the 'if' statement and take either the 'then_part'
- *       or 'else_part'. */
-
 	if (get_token(hawk) <= -1) goto oops;
 
 	tloc = hawk->tok.loc;
@@ -3189,12 +3332,8 @@ static hawk_nde_t* parse_if (hawk_t* hawk, const hawk_loc_t* xloc)
 		{
 			hawk_nde_t* null_nde;
 
-			null_nde = (hawk_nde_t*)hawk_callocmem(hawk, HAWK_SIZEOF(*null_nde));
-			if (HAWK_UNLIKELY(!null_nde))
-			{
-				ADJERR_LOC(hawk, xloc);
-				goto oops;
-			}
+			null_nde = make_null_nde(hawk, xloc);
+			if (HAWK_UNLIKELY(!null_nde)) goto oops;
 
 			/* [BE CAREFUL]
 			 * Don't forget reset test and then_part to HAWK_NULL if the control
@@ -3202,8 +3341,6 @@ static hawk_nde_t* parse_if (hawk_t* hawk, const hawk_loc_t* xloc)
 			hawk_clrpt(hawk, test);
 			hawk_clrpt(hawk, then_part);
 
-			null_nde->type = HAWK_NDE_NULL;
-			null_nde->loc = *xloc;
 			return null_nde;
 		}
 	}
@@ -3480,18 +3617,12 @@ static hawk_nde_t* parse_while (hawk_t* hawk, const hawk_loc_t* xloc)
 		/* fold while(0) and while(@false) into a null statement. */
 		hawk_nde_t* null_nde;
 
-		null_nde = (hawk_nde_t*)hawk_callocmem(hawk, HAWK_SIZEOF(*null_nde));
-		if (HAWK_UNLIKELY(!null_nde))
-		{
-			ADJERR_LOC(hawk, xloc);
-			goto oops;
-		}
+		null_nde = make_null_nde(hawk, xloc);
+		if (HAWK_UNLIKELY(!null_nde)) goto oops;
 
 		hawk_clrpt(hawk, body); body = HAWK_NULL;
 		hawk_clrpt(hawk, test); test = HAWK_NULL;
 
-		null_nde->type = HAWK_NDE_NULL;
-		null_nde->loc = *xloc;
 		return null_nde;
 	}
 
@@ -4342,20 +4473,12 @@ static hawk_nde_t* parse_statement (hawk_t* hawk, const hawk_loc_t* xloc)
 	if (MATCH(hawk,TOK_SEMICOLON))
 	{
 		/* null statement */
-		nde = (hawk_nde_t*)hawk_callocmem(hawk, HAWK_SIZEOF(*nde));
-		if (HAWK_UNLIKELY(!nde))
-		{
-			ADJERR_LOC(hawk, xloc);
-			return HAWK_NULL;
-		}
-
-		nde->type = HAWK_NDE_NULL;
-		nde->loc = *xloc;
-		nde->next = HAWK_NULL;
+		nde = make_null_nde(hawk, xloc);
+		if (HAWK_UNLIKELY(!nde)) return HAWK_NULL;
 
 		if (get_token(hawk) <= -1)
 		{
-			hawk_freemem(hawk, nde);
+			hawk_clrpt(hawk, nde);
 			return HAWK_NULL;
 		}
 	}
@@ -4392,6 +4515,15 @@ static hawk_nde_t* parse_statement (hawk_t* hawk, const hawk_loc_t* xloc)
 		hawk->parse.id.stmt = old_id;
 	}
 
+	if (nde && !does_nde_have_side_effect(nde))
+	{
+		hawk_nde_t* tmp;
+		tmp = make_null_nde(hawk, &nde->loc);
+		hawk_clrpt(hawk, nde);
+		if (HAWK_UNLIKELY(!tmp)) return HAWK_NULL;
+		nde = tmp;
+	}
+
 	return nde;
 }
 
@@ -4430,7 +4562,7 @@ static hawk_nde_t* parse_expr_basic (hawk_t* hawk, const hawk_loc_t* xloc)
 	hawk_nde_t* nde, * n1, * n2;
 
 	nde = parse_logical_or(hawk, xloc);
-	if (nde == HAWK_NULL) return HAWK_NULL;
+	if (!nde) return HAWK_NULL;
 
 	if (MATCH(hawk,TOK_QUEST))
 	{
@@ -4445,7 +4577,7 @@ static hawk_nde_t* parse_expr_basic (hawk_t* hawk, const hawk_loc_t* xloc)
 
 		eloc = hawk->tok.loc;
 		n1 = parse_expr_withdc(hawk, &eloc);
-		if (n1 == HAWK_NULL)
+		if (!n1)
 		{
 			hawk_clrpt(hawk, nde);
 			return HAWK_NULL;
@@ -4467,7 +4599,7 @@ static hawk_nde_t* parse_expr_basic (hawk_t* hawk, const hawk_loc_t* xloc)
 
 		eloc = hawk->tok.loc;
 		n2 = parse_expr_withdc(hawk, &eloc);
-		if (n2 == HAWK_NULL)
+		if (!n2)
 		{
 			hawk_clrpt(hawk, nde);
 			hawk_clrpt(hawk, n1);
@@ -4475,7 +4607,7 @@ static hawk_nde_t* parse_expr_basic (hawk_t* hawk, const hawk_loc_t* xloc)
 		}
 
 		cnd = (hawk_nde_cnd_t*)hawk_callocmem(hawk, HAWK_SIZEOF(*cnd));
-		if (cnd == HAWK_NULL)
+		if (HAWK_UNLIKELY(!cnd))
 		{
 			hawk_clrpt(hawk, nde);
 			hawk_clrpt(hawk, n1);
@@ -7403,18 +7535,14 @@ static hawk_nde_t* parse_idx_chain (hawk_t* hawk, const hawk_loc_t* xloc)
 
 		/* additional index - a[10][20] or a.b.c ...
 		 * use the NULL node as a splitter */
-		splitter = (hawk_nde_t*)hawk_callocmem(hawk, HAWK_SIZEOF(*splitter));
-		if (HAWK_UNLIKELY(!splitter))
-		{
-			ADJERR_LOC(hawk, xloc);
-			goto oops;
-		}
 
-		splitter->type = HAWK_NDE_NULL;
+		splitter = make_null_nde(hawk, xloc);
+		if (HAWK_UNLIKELY(!splitter)) goto oops;
 
 		HAWK_ASSERT(idx.tail != HAWK_NULL);
 		idx.tail->next = splitter;
 		idx.tail = splitter;
+		/* splitter is already chained. no need seperate clearing upon failure */
 
 		if (parse_single_idx(hawk, &idx) <= -1) goto oops;
 	}