[committed] jit: handle equality of function pointer types

[committed] jit: handle equality of function pointer types

[David Malcolm]

libgccjit was being overzealous when type-checking function pointers,
requiring exact pointer equality of recording::function_type
instances, defeating attempts by client code to work with function
pointers as data.

This patch removes the overzealous checking, and should allow
function pointers to be used as expected.

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu;
takes jit.sum from 9889 to 9909 PASS results.

Committed to trunk as r253255.

gcc/jit/ChangeLog:
	* jit-recording.c
	(gcc::jit::recording::function_type::is_same_type_as): New function.
	* jit-recording.h: In namespace gcc::jit::recording::
	(type::accepts_writes_from): Use is_same_type_as rather than pointer
	equality.
	(type::is_same_type_as): New virtual function.
	(function_type::is_same_type_as): New override.

gcc/testsuite/ChangeLog:
	* jit.dg/test-error-mismatching-types-in-assignment-fn-ptr.c: New
	test case.
	* jit.dg/test-returning-function-ptr.c (create_code): Update to
	create a function pointer type independently of the call to
	gcc_jit_function_get_address, and assign the pointer to a local
	before returning it, to exercise the function pointer type
	comparison code.
---
 gcc/jit/jit-recording.c                            | 47 +++++++++++
 gcc/jit/jit-recording.h                            |  9 ++-
 ...-error-mismatching-types-in-assignment-fn-ptr.c | 92 ++++++++++++++++++++++
 gcc/testsuite/jit.dg/test-returning-function-ptr.c | 33 ++++++--
 4 files changed, 173 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/jit.dg/test-error-mismatching-types-in-assignment-fn-ptr.c

diff --git a/gcc/jit/jit-recording.c b/gcc/jit/jit-recording.c
index 8481280..6d7dc80 100644
--- a/gcc/jit/jit-recording.c
+++ b/gcc/jit/jit-recording.c
@@ -2643,6 +2643,53 @@ recording::function_type::dereference ()
   return NULL;
 }
 
+/* Implementation of virtual hook recording::type::is_same_type_as for
+   recording::function_type.
+
+   We override this to avoid requiring identity of function pointer types,
+   so that if client code has obtained the same signature in
+   different ways (e.g. via gcc_jit_context_new_function_ptr_type
+   vs gcc_jit_function_get_address), the different function_type
+   instances are treated as compatible.
+
+   We can't use type::accepts_writes_from for this as we need a stronger
+   notion of "sameness": if we have a fn_ptr type that has args that are
+   themselves fn_ptr types, then those args still need to match exactly.
+
+   Alternatively, we could consolidate attempts to create identical
+   function_type instances so that pointer equality works, but that runs
+   into issues about the lifetimes of the cache (w.r.t. nested contexts).  */
+
+bool
+recording::function_type::is_same_type_as (type *other)
+{
+  gcc_assert (other);
+
+  function_type *other_fn_type = other->dyn_cast_function_type ();
+  if (!other_fn_type)
+    return false;
+
+  /* Everything must match.  */
+
+  if (!m_return_type->is_same_type_as (other_fn_type->m_return_type))
+    return false;
+
+  if (m_param_types.length () != other_fn_type->m_param_types.length ())
+    return false;
+
+  unsigned i;
+  type *param_type;
+  FOR_EACH_VEC_ELT (m_param_types, i, param_type)
+    if (!param_type->is_same_type_as (other_fn_type->m_param_types[i]))
+      return false;
+
+  if (m_is_variadic != other_fn_type->m_is_variadic)
+    return false;
+
+  /* Passed all tests.  */
+  return true;
+}
+
 /* Implementation of pure virtual hook recording::memento::replay_into
    for recording::function_type.  */
 
diff --git a/gcc/jit/jit-recording.h b/gcc/jit/jit-recording.h
index 8918124..9123645 100644
--- a/gcc/jit/jit-recording.h
+++ b/gcc/jit/jit-recording.h
@@ -491,7 +491,12 @@ public:
   virtual bool accepts_writes_from (type *rtype)
   {
     gcc_assert (rtype);
-    return this->unqualified () == rtype->unqualified ();
+    return this->unqualified ()->is_same_type_as (rtype->unqualified ());
+  }
+
+  virtual bool is_same_type_as (type *other)
+  {
+    return this == other;
   }
 
   /* Strip off "const" etc */
@@ -751,6 +756,8 @@ public:
   function_type *dyn_cast_function_type () FINAL OVERRIDE { return this; }
   function_type *as_a_function_type () FINAL OVERRIDE { return this; }
 
+  bool is_same_type_as (type *other) FINAL OVERRIDE;
+
   bool is_int () const FINAL OVERRIDE { return false; }
   bool is_float () const FINAL OVERRIDE { return false; }
   bool is_bool () const FINAL OVERRIDE { return false; }
diff --git a/gcc/testsuite/jit.dg/test-error-mismatching-types-in-assignment-fn-ptr.c b/gcc/testsuite/jit.dg/test-error-mismatching-types-in-assignment-fn-ptr.c
new file mode 100644
index 0000000..4faa3b4
--- /dev/null
+++ b/gcc/testsuite/jit.dg/test-error-mismatching-types-in-assignment-fn-ptr.c
@@ -0,0 +1,92 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "libgccjit.h"
+
+#include "harness.h"
+
+void
+create_code (gcc_jit_context *ctxt, void *user_data)
+{
+  /* Let's try to inject the equivalent of:
+
+     typedef void (*fn_ptr_iii) (int, int, int);
+     typedef void (*fn_ptr_ifi) (int, float, int);
+     void
+     test_fn (void)
+     {
+        fn_ptr_iii iii_ptr;
+        fn_ptr_ifi ifi_ptr;
+
+	iii_ptr = NULL;
+	ifi_ptr = iii_ptr;
+     }
+
+     and verify that the API complains about the mismatching types
+     in the second assignment (but not the first).
+  */
+  gcc_jit_type *void_type =
+    gcc_jit_context_get_type (ctxt, GCC_JIT_TYPE_VOID);
+  gcc_jit_type *int_type =
+    gcc_jit_context_get_type (ctxt, GCC_JIT_TYPE_INT);
+  gcc_jit_type *float_type =
+    gcc_jit_context_get_type (ctxt, GCC_JIT_TYPE_FLOAT);
+
+  gcc_jit_type *iii_types[] = {int_type, int_type, int_type};
+  gcc_jit_type *fn_ptr_type_iii
+    = gcc_jit_context_new_function_ptr_type (ctxt, NULL,
+					     void_type,
+					     3, iii_types,
+					     0);
+
+  gcc_jit_type *ifi_types[] = {int_type, float_type, int_type};
+  gcc_jit_type *fn_ptr_type_ifi
+    = gcc_jit_context_new_function_ptr_type (ctxt, NULL,
+					     void_type,
+					     3, ifi_types,
+					     0);
+
+  gcc_jit_function *test_fn =
+    gcc_jit_context_new_function (ctxt, NULL,
+                                  GCC_JIT_FUNCTION_EXPORTED,
+                                  void_type,
+                                  "test_fn",
+                                  0, NULL,
+                                  0);
+  gcc_jit_lvalue *iii_ptr =
+    gcc_jit_function_new_local (
+      test_fn, NULL, fn_ptr_type_iii, "iii_ptr");
+  gcc_jit_lvalue *ifi_ptr =
+    gcc_jit_function_new_local (
+      test_fn, NULL, fn_ptr_type_ifi, "ifi_ptr");
+
+  gcc_jit_block *block = gcc_jit_function_new_block (test_fn, NULL);
+
+  /* iii_ptr = NULL; */
+  gcc_jit_block_add_assignment (
+    block, NULL,
+    iii_ptr,
+    gcc_jit_context_null (ctxt, fn_ptr_type_iii));
+  /* ifi_ptr = iii_ptr; */
+  gcc_jit_block_add_assignment (
+    block, NULL,
+    ifi_ptr,
+    gcc_jit_lvalue_as_rvalue (iii_ptr));
+  gcc_jit_block_end_with_void_return (block, NULL);
+}
+
+void
+verify_code (gcc_jit_context *ctxt, gcc_jit_result *result)
+{
+  CHECK_VALUE (result, NULL);
+
+  /* Verify that the correct error message was emitted.  */
+  CHECK_STRING_VALUE (gcc_jit_context_get_first_error (ctxt),
+		      "gcc_jit_block_add_assignment:"
+		      " mismatching types:"
+		      " assignment to ifi_ptr"
+		      " (type: void (*) (int, float, int))"
+		      " from iii_ptr"
+		      " (type: void (*) (int, int, int))");
+}
+
diff --git a/gcc/testsuite/jit.dg/test-returning-function-ptr.c b/gcc/testsuite/jit.dg/test-returning-function-ptr.c
index 2d4f01e..f96079c 100644
--- a/gcc/testsuite/jit.dg/test-returning-function-ptr.c
+++ b/gcc/testsuite/jit.dg/test-returning-function-ptr.c
@@ -28,10 +28,15 @@ create_code (gcc_jit_context *ctxt, void *user_data)
         internally_called_function (a * 3, a * 4, a * 5);
      }
 
-     void (*) (int)
+     typedef void (*fn_ptr_type) (int);
+
+     fn_ptr_type
      get_test_caller (void)
      {
-       return internal_test_caller;
+       // Verify that we can assign function pointers to variables
+       fn_ptr_type p;
+       p = internal_test_caller;
+       return p;
      }
   */
   int i;
@@ -87,11 +92,11 @@ create_code (gcc_jit_context *ctxt, void *user_data)
 			      3, args));
   gcc_jit_block_end_with_void_return (block, NULL);
 
-  gcc_jit_rvalue *fn_ptr
-    = gcc_jit_function_get_address (test_caller, NULL);
-
   gcc_jit_type *fn_ptr_type
-    = gcc_jit_rvalue_get_type (fn_ptr);
+    = gcc_jit_context_new_function_ptr_type (ctxt, NULL,
+					     void_type,
+					     1, &int_type,
+					     0);
 
   /* Build the get_test_caller fn.  */
   gcc_jit_function *get_test_caller =
@@ -102,7 +107,21 @@ create_code (gcc_jit_context *ctxt, void *user_data)
 				  0, NULL,
 				  0);
   block = gcc_jit_function_new_block (get_test_caller, NULL);
-  gcc_jit_block_end_with_return (block, NULL, fn_ptr);
+
+  /* fn_ptr_type p; */
+  gcc_jit_lvalue *local_p
+    = gcc_jit_function_new_local (get_test_caller, NULL,
+				  fn_ptr_type, "p");
+
+  /* p = internal_test_caller; */
+  gcc_jit_block_add_assignment (block, NULL,
+				local_p,
+				gcc_jit_function_get_address (test_caller,
+							      NULL));
+
+  /* return p; */
+  gcc_jit_block_end_with_return (block, NULL,
+				 gcc_jit_lvalue_as_rvalue (local_p));
 }
 
 static int called_with[3];
-- 
1.8.5.3