Convert some EVALUATE statements to switch statement (#504)

Author: yutaro-sakamoto

cobj/codegen.c

@@ -3549,6 +3549,47 @@ static void joutput_ferror_stmt(struct cb_statement *p, int code) {
 //   joutput_line("// %s:%d: %s", p->file, p->line, p->comment);
 // }
 
+static void joutput_switch(struct cb_switch *sw,
+                           enum joutput_stmt_type output_type) {
+  joutput_prefix();
+  joutput("switch(");
+  joutput_param(sw->test, -1);
+  joutput(".getInt()) {");
+  joutput_newline();
+  joutput_indent_level += 2;
+  cb_tree case_tree;
+  for (case_tree = sw->case_list; case_tree; case_tree = CB_CHAIN(case_tree)) {
+    cb_tree whens = CB_VALUE(case_tree);
+    cb_tree stmt = CB_VALUE(whens);
+    int flag_other_exists = 1;
+    for (; whens; whens = CB_CHAIN(whens)) {
+      cb_tree objs = CB_VALUE(whens);
+      for (; objs; objs = CB_CHAIN(objs)) {
+        cb_tree obj = CB_VALUE(objs);
+        if (obj && CB_LIST_P(obj)) {
+          flag_other_exists = 0;
+        }
+        if (obj && CB_PAIR_P(obj)) {
+          cb_tree when_target = CB_PAIR_Y(obj);
+          struct cb_literal *primary_target =
+              CB_LITERAL(CB_PAIR_X(when_target));
+          int dummy;
+          int label =
+              cb_literal_to_int_for_switch_label(primary_target, &dummy);
+          joutput_line("case %d:", label);
+        }
+      }
+    }
+    if (flag_other_exists) {
+      joutput_line("default:");
+    }
+    joutput_stmt(stmt, output_type);
+    joutput_line("break;");
+  }
+  joutput_indent_level -= 2;
+  joutput_line("}");
+}
+
 static void joutput_stmt(cb_tree x, enum joutput_stmt_type output_type) {
   struct cb_statement *p;
   struct cb_label *lp;
@@ -3948,6 +3989,9 @@ static void joutput_stmt(cb_tree x, enum joutput_stmt_type output_type) {
     joutput_prefix();
     joutput(";\n");
     break;
+  case CB_TAG_SWITCH:
+    joutput_switch(CB_SWITCH(x), output_type);
+    break;
   case CB_TAG_LIST:
     if (x && CB_TREE_TAG(CB_VALUE(x)) == CB_TAG_PERFORM) {
       putParen = 0;

cobj/tree.c

@@ -2511,6 +2511,19 @@ cb_tree cb_build_continue(void) {
   return CB_TREE(p);
 }
 
+/*
+ * SWITCH
+ */
+
+cb_tree cb_build_switch(cb_tree test, cb_tree case_list) {
+  struct cb_switch *p;
+
+  p = make_tree(CB_TAG_SWITCH, CB_CATEGORY_UNKNOWN, sizeof(struct cb_switch));
+  p->test = test;
+  p->case_list = case_list;
+  return CB_TREE(p);
+}
+
 /*
  * FUNCTION
  */

cobj/tree.h

@@ -85,6 +85,8 @@ enum cb_tag {
 
   CB_TAG_JAVA_CONTINUE,
   CB_TAG_JAVA_BREAK,
+
+  CB_TAG_SWITCH,
 };
 
 enum cb_alphabet_name_type {
@@ -1118,6 +1120,24 @@ extern cb_tree cb_build_perform(int type);
 extern cb_tree cb_build_perform_varying(cb_tree name, cb_tree from,
                                         cb_tree step, cb_tree until);
 
+/*
+ * switch (evaluate)
+ */
+
+struct cb_switch {
+  struct cb_tree_common common;
+  cb_tree test;
+  cb_tree case_list;
+};
+
+#define CB_SWITCH(x) (CB_TREE_CAST(CB_TAG_SWITCH, struct cb_switch, x))
+#define CB_SWITCH_P(x) (CB_TREE_TAG(x) == CB_TAG_SWITCH)
+
+extern cb_tree cb_build_switch(cb_tree test, cb_tree case_tree);
+
+extern int cb_literal_to_int_for_switch_label(struct cb_literal *lit,
+                                              int *result);
+
 /*
  * SORT
  */

cobj/typeck.c

@@ -3673,8 +3673,154 @@ static cb_tree build_evaluate(cb_tree subject_list, cb_tree case_list) {
   }
 }
 
+int cb_literal_to_int_for_switch_label(struct cb_literal *lit, int *result) {
+  const char *min_num_abs =
+      "2147483648";                   // -1 * (the minimum value of int of Java)
+  const char *max_num = "2147483647"; // the maximum value of int of Java
+  const int len_boundary =
+      10; // string length of min_num_abs (== string length of max_num)
+  if (lit->size > len_boundary) {
+    // the value of the literal is out of range
+    *result = 0;
+    return 0;
+  }
+
+  size_t i;
+  const char *boundary = lit->sign < 0 ? min_num_abs : max_num;
+  if (lit->size == len_boundary) {
+    for (i = 0; i < len_boundary; ++i) {
+      if (boundary[i] < lit->data[i]) {
+        // the value of the literal is out of range
+        *result = 0;
+        return 0;
+      }
+    }
+  }
+
+  int ret = 0;
+  for (i = 0; i < lit->size; ++i) {
+    ret = ret * 10 + lit->data[i] - '0';
+  }
+  *result = 1;
+  return lit->sign < 0 ? -ret : ret;
+}
+
+// Determine a given label exists in the list of existing labels
+// If a given label exists in the list, return 1. Otherwise return 0;
+static int is_switch_label_duplicate(int label, const int *existing_label_list,
+                                     int list_len) {
+  int i = 0;
+  for (; i < list_len; ++i) {
+    if (existing_label_list[i] == label) {
+      return 1;
+    }
+  }
+  return 0;
+}
+
+static cb_tree convert_evaluate_stmt_to_switch_stmt(cb_tree subject_list,
+                                                    cb_tree case_list) {
+  cb_tree subjs;
+  cb_tree whens;
+  cb_tree objs;
+
+  cb_tree case_tree = case_list;
+  int when_count = 0;
+  int other_exists = 0;
+
+  // The length of subject_list must be 1
+  if (subject_list == NULL || CB_CHAIN(subject_list)) {
+    return NULL;
+  }
+
+  // Determine if a given evaluate statement can be converted to a switch
+  // statement
+  int case_count = 0;
+  for (; case_tree; case_tree = CB_CHAIN(case_tree), ++case_count) {
+    whens = CB_VALUE(case_tree);
+    /* for each WHEN sequence */
+    int flag_other_exists = 1;
+    for (; whens; whens = CB_CHAIN(whens)) {
+      for (subjs = subject_list, objs = CB_VALUE(whens); subjs && objs;
+           subjs = CB_CHAIN(subjs), objs = CB_CHAIN(objs)) {
+        cb_tree subj = CB_VALUE(subjs);
+        cb_tree obj = CB_VALUE(objs);
+        if (!subj || CB_TREE_CATEGORY(subj) != CB_CATEGORY_NUMERIC) {
+          return NULL;
+        }
+        if (obj) {
+          if (CB_LIST_P(obj)) {
+            flag_other_exists = 0;
+          }
+          if (CB_STATEMENT_P(obj)) {
+            continue;
+          }
+          if (CB_PAIR_P(obj)) {
+            // WHEN NOT
+            if (CB_PURPOSE_INT(obj)) {
+              return NULL;
+            }
+            cb_tree when_target = CB_PAIR_Y(obj);
+            if (CB_PAIR_P(when_target)) {
+              cb_tree primary_target = CB_PAIR_X(when_target);
+              cb_tree thru_target = CB_PAIR_Y(when_target);
+              if (!CB_LITERAL_P(primary_target) || thru_target) {
+                return NULL;
+              }
+              struct cb_literal *lit = CB_LITERAL(primary_target);
+              if (lit->data == NULL || lit->scale != 0) {
+                return NULL;
+              }
+              ++when_count;
+            }
+          }
+        }
+      }
+    }
+    other_exists |= flag_other_exists;
+  }
+  // Build Switch statement
+  int *cases = malloc(when_count * sizeof(int));
+  int case_index = 0;
+  for (case_tree = case_list; case_tree; case_tree = CB_CHAIN(case_tree)) {
+    whens = CB_VALUE(case_tree);
+    /* for each WHEN sequence */
+    for (; whens; whens = CB_CHAIN(whens)) {
+      for (objs = CB_VALUE(whens); objs; objs = CB_CHAIN(objs)) {
+        cb_tree obj = CB_VALUE(objs);
+        if (obj && CB_PAIR_P(obj)) {
+          cb_tree when_target = CB_PAIR_Y(obj);
+          struct cb_literal *primary_target =
+              CB_LITERAL(CB_PAIR_X(when_target));
+          int result;
+          int label =
+              cb_literal_to_int_for_switch_label(primary_target, &result);
+          // If calculating a switch label fails, the evaluate statement cannot
+          // be converted to switch statement
+          if (!result) {
+            return NULL;
+          }
+          // If a duplicate label is found, the evaluate statement cannot be
+          // converted to switch statement
+          if (is_switch_label_duplicate(label, cases, case_index)) {
+            return NULL;
+          }
+          cases[case_index++] = label;
+        }
+      }
+    }
+  }
+  return cb_build_switch(CB_VALUE(subject_list), case_list);
+}
+
 void cb_emit_evaluate(cb_tree subject_list, cb_tree case_list) {
-  cb_emit(build_evaluate(subject_list, case_list));
+  cb_tree switch_stmt =
+      convert_evaluate_stmt_to_switch_stmt(subject_list, case_list);
+  if (switch_stmt) {
+    cb_emit(switch_stmt);
+  } else {
+    cb_emit(build_evaluate(subject_list, case_list));
+  }
 }
 
 /*

tests/Makefile.am

@@ -217,7 +217,8 @@ misc_DEPENDENCIES = \
 	misc.src/record-key-duplicates-error.at \
 	misc.src/copy-comments.at \
 	misc.src/read_prev_after_start.at \
-	misc.src/japanese-char-section-var.at
+	misc.src/japanese-char-section-var.at \
+	misc.src/evaluate-switch.at
 
 EXTRA_DIST = $(srcdir)/package.m4 \
 	$(TESTS) \

tests/Makefile.in

@@ -758,7 +758,8 @@ misc_DEPENDENCIES = \
 	misc.src/record-key-duplicates-error.at \
 	misc.src/copy-comments.at \
 	misc.src/read_prev_after_start.at \
-	misc.src/japanese-char-section-var.at
+	misc.src/japanese-char-section-var.at \
+	misc.src/evaluate-switch.at
 
 EXTRA_DIST = $(srcdir)/package.m4 \
 	$(TESTS) \

tests/misc.at

@@ -47,3 +47,4 @@ m4_include([record-key-duplicates-error.at])
 #m4_include([copy-comments.at])
 m4_include([read_prev_after_start.at])
 m4_include([japanese-char-section-var.at])
+m4_include([evaluate-switch.at])