From 1433b404d68f9fe314ae2955d0988dd74e5ecb92 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Sun, 6 Sep 2020 21:06:56 +0900
Subject: [PATCH] [GNU] Add __builtin_types_compatible_p

---
 chibicc.h      |  2 ++
 parse.c        | 10 ++++++++++
 test/builtin.c | 33 +++++++++++++++++++++++++++++++++
 type.c         | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 92 insertions(+)
 create mode 100644 test/builtin.c

diff --git a/chibicc.h b/chibicc.h
index a418d52..fc6ca6d 100644
--- a/chibicc.h
+++ b/chibicc.h
@@ -284,6 +284,7 @@ struct Type {
   int size;           // sizeof() value
   int align;          // alignment
   bool is_unsigned;   // unsigned or signed
+  Type *origin;       // for type compatibility check
 
   // Pointer-to or array-of type. We intentionally use the same member
   // to represent pointer/array duality in C.
@@ -348,6 +349,7 @@ extern Type *ty_double;
 bool is_integer(Type *ty);
 bool is_flonum(Type *ty);
 bool is_numeric(Type *ty);
+bool is_compatible(Type *t1, Type *t2);
 Type *copy_type(Type *ty);
 Type *pointer_to(Type *base);
 Type *func_type(Type *return_ty);
diff --git a/parse.c b/parse.c
index 1fe83d8..ea6ff50 100644
--- a/parse.c
+++ b/parse.c
@@ -2611,6 +2611,7 @@ static Node *funcall(Token **rest, Token *tok, Node *fn) {
 //         | "sizeof" unary
 //         | "_Alignof" "(" type-name ")"
 //         | "_Alignof" unary
+//         | "__builtin_types_compatible_p" "(" type-name, type-name, ")"
 //         | "__builtin_reg_class" "(" type-name ")"
 //         | ident
 //         | str
@@ -2656,6 +2657,15 @@ static Node *primary(Token **rest, Token *tok) {
     return new_ulong(node->ty->align, tok);
   }
 
+  if (equal(tok, "__builtin_types_compatible_p")) {
+    tok = skip(tok->next, "(");
+    Type *t1 = typename(&tok, tok);
+    tok = skip(tok, ",");
+    Type *t2 = typename(&tok, tok);
+    *rest = skip(tok, ")");
+    return new_num(is_compatible(t1, t2), start);
+  }
+
   if (equal(tok, "__builtin_reg_class")) {
     tok = skip(tok->next, "(");
     Type *ty = typename(&tok, tok);
diff --git a/test/builtin.c b/test/builtin.c
new file mode 100644
index 0000000..178c555
--- /dev/null
+++ b/test/builtin.c
@@ -0,0 +1,33 @@
+#include "test.h"
+
+int main() {
+  ASSERT(1, __builtin_types_compatible_p(int, int));
+  ASSERT(1, __builtin_types_compatible_p(double, double));
+  ASSERT(0, __builtin_types_compatible_p(int, long));
+  ASSERT(0, __builtin_types_compatible_p(long, float));
+  ASSERT(1, __builtin_types_compatible_p(int *, int *));
+  ASSERT(0, __builtin_types_compatible_p(short *, int *));
+  ASSERT(0, __builtin_types_compatible_p(int **, int *));
+  ASSERT(1, __builtin_types_compatible_p(const int, int));
+  ASSERT(0, __builtin_types_compatible_p(unsigned, int));
+  ASSERT(1, __builtin_types_compatible_p(signed, int));
+  ASSERT(0, __builtin_types_compatible_p(struct {int a;}, struct {int a;}));
+
+  ASSERT(1, __builtin_types_compatible_p(int (*)(void), int (*)(void)));
+  ASSERT(1, __builtin_types_compatible_p(void (*)(int), void (*)(int)));
+  ASSERT(1, __builtin_types_compatible_p(void (*)(int, double), void (*)(int, double)));
+  ASSERT(1, __builtin_types_compatible_p(int (*)(float, double), int (*)(float, double)));
+  ASSERT(0, __builtin_types_compatible_p(int (*)(float, double), int));
+  ASSERT(0, __builtin_types_compatible_p(int (*)(float, double), int (*)(float)));
+  ASSERT(0, __builtin_types_compatible_p(int (*)(float, double), int (*)(float, double, int)));
+  ASSERT(1, __builtin_types_compatible_p(double (*)(...), double (*)(...)));
+  ASSERT(0, __builtin_types_compatible_p(double (*)(...), double (*)(void)));
+
+  ASSERT(1, ({ typedef struct {int a;} T; __builtin_types_compatible_p(T, T); }));
+  ASSERT(1, ({ typedef struct {int a;} T; __builtin_types_compatible_p(T, const T); }));
+
+  ASSERT(1, ({ struct {int a; int b;} x; __builtin_types_compatible_p(typeof(x.a), typeof(x.b)); }));
+
+  printf("OK\n");
+  return 0;
+}
diff --git a/type.c b/type.c
index b50c3c3..a774f09 100644
--- a/type.c
+++ b/type.c
@@ -38,9 +38,56 @@ bool is_numeric(Type *ty) {
   return is_integer(ty) || is_flonum(ty);
 }
 
+bool is_compatible(Type *t1, Type *t2) {
+  if (t1 == t2)
+    return true;
+
+  if (t1->origin)
+    return is_compatible(t1->origin, t2);
+
+  if (t2->origin)
+    return is_compatible(t1, t2->origin);
+
+  if (t1->kind != t2->kind)
+    return false;
+
+  switch (t1->kind) {
+  case TY_CHAR:
+  case TY_SHORT:
+  case TY_INT:
+  case TY_LONG:
+    return t1->is_unsigned == t2->is_unsigned;
+  case TY_FLOAT:
+  case TY_DOUBLE:
+    return true;
+  case TY_PTR:
+    return is_compatible(t1->base, t2->base);
+  case TY_FUNC: {
+    if (!is_compatible(t1->return_ty, t2->return_ty))
+      return false;
+    if (t1->is_variadic != t2->is_variadic)
+      return false;
+
+    Type *p1 = t1->params;
+    Type *p2 = t2->params;
+    for (; p1 && p2; p1 = p1->next, p2 = p2->next)
+      if (!is_compatible(p1, p2))
+        return false;
+    return p1 == NULL && p2 == NULL;
+  }
+  case TY_ARRAY:
+    if (!is_compatible(t1->base, t2->base))
+      return false;
+    return t1->array_len < 0 && t2->array_len < 0 &&
+           t1->array_len == t2->array_len;
+  }
+  return false;
+}
+
 Type *copy_type(Type *ty) {
   Type *ret = calloc(1, sizeof(Type));
   *ret = *ty;
+  ret->origin = ty;
   return ret;
 }
 
-- 
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