x86: Honor alignment of arguments

Darwin aligns long-double to 16, and thus all of the long double
tests were failing due to not honoring that.  We ought to be able
to devise a test case for GCC using __attribute__((aligned)) that
would have failed too.

diff --git a/src/x86/ffi.c b/src/x86/ffi.c
index 4c96c6d..c4d740a 100644 (file)
--- a/src/x86/ffi.c
+++ b/src/x86/ffi.c
@@ -332,13 +332,28 @@ ffi_call_int (ffi_cif *cif, void (*fn)(void), void *rvalue,
       else
        {
          size_t za = ALIGN (z, FFI_SIZEOF_ARG);
+         size_t align = FFI_SIZEOF_ARG;
+
+         /* Alignment rules for arguments are quite complex.  Vectors and
+            structures with 16 byte alignment get it.  Note that long double
+            on Darwin does have 16 byte alignment, and does not get this
+            alignment if passed directly; a structure with a long double
+            inside, however, would get 16 byte alignment.  Since libffi does
+            not support vectors, we need non concern ourselves with other
+            cases.  */
+         if (t == FFI_TYPE_STRUCT && ty->alignment >= 16)
+           align = 16;
+           
          if (dir < 0)
            {
+             /* ??? These reverse argument ABIs are probably too old
+                to have cared about alignment.  Someone should check.  */
              argp -= za;
              memcpy (argp, valp, z);
            }
          else
            {
+             argp = (char *)ALIGN (argp, align);
              memcpy (argp, valp, z);
              argp += za;
            }
@@ -419,8 +434,9 @@ ffi_closure_inner (struct closure_frame *frame, char *stack)
   arg_types = cif->arg_types;
   for (i = 0; i < n; ++i)
     {
-      size_t z = arg_types[i]->size;
-      int t = arg_types[i]->type;
+      ffi_type *ty = arg_types[i];
+      size_t z = ty->size;
+      int t = ty->type;
       void *valp;
 
       if (z <= FFI_SIZEOF_ARG && t != FFI_TYPE_STRUCT)
@@ -441,13 +457,22 @@ ffi_closure_inner (struct closure_frame *frame, char *stack)
       else
        {
          size_t za = ALIGN (z, FFI_SIZEOF_ARG);
+         size_t align = FFI_SIZEOF_ARG;
+
+         /* See the comment in ffi_call_int.  */
+         if (t == FFI_TYPE_STRUCT && ty->alignment >= 16)
+           align = 16;
+
          if (dir < 0)
            {
+             /* ??? These reverse argument ABIs are probably too old
+                to have cared about alignment.  Someone should check.  */
              argp -= za;
              valp = argp;
            }
          else
            {
+             argp = (char *)ALIGN (argp, align);
              valp = argp;
              argp += za;
            }