[PATCH] Fix passing struct by value on aarch64

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[PATCH] Fix passing struct by value on aarch64

Andreas Schwab
This fixes the Python ctype tests.

---
 src/aarch64/ffi.c | 39 +++++++++++++++++++++++++++++++--------
 1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/aarch64/ffi.c b/src/aarch64/ffi.c
index c4a6151d37..05a1b8a9a2 100644
--- a/src/aarch64/ffi.c
+++ b/src/aarch64/ffi.c
@@ -238,13 +238,18 @@ is_vfp_type (const ffi_type *ty)
    state.
 
    The terse state variable names match the names used in the AARCH64
-   PCS. */
+   PCS.
+
+   The struct area is allocated downwards from the top of the argument
+   area.  It is used to hold copies of structures passed by value that are
+   bigger than 16 bytes.  */
 
 struct arg_state
 {
   unsigned ngrn;                /* Next general-purpose register number. */
   unsigned nsrn;                /* Next vector register number. */
   size_t nsaa;                  /* Next stack offset. */
+  size_t next_struct_area; /* Place to allocate big structs. */
 
 #if defined (__APPLE__)
   unsigned allocating_variadic;
@@ -253,11 +258,12 @@ struct arg_state
 
 /* Initialize a procedure call argument marshalling state.  */
 static void
-arg_init (struct arg_state *state)
+arg_init (struct arg_state *state, size_t size)
 {
   state->ngrn = 0;
   state->nsrn = 0;
   state->nsaa = 0;
+  state->next_struct_area = size;
 #if defined (__APPLE__)
   state->allocating_variadic = 0;
 #endif
@@ -286,6 +292,21 @@ allocate_to_stack (struct arg_state *state, void *stack,
   return (char *)stack + nsaa;
 }
 
+/* Allocate and copy a structure that is passed by value on the stack and
+   return a pointer to it.  */
+static void *
+allocate_and_copy_struct_to_stack (struct arg_state *state, void *stack,
+   size_t alignment, size_t size, void *value)
+{
+  size_t dest = state->next_struct_area - size;
+
+  /* Round down to the natural alignment of the value.  */
+  dest = ALIGN_DOWN (dest, alignment);
+  state->next_struct_area = dest;
+
+  return memcpy ((char *) stack + dest, value, size);
+}
+
 static ffi_arg
 extend_integer_type (void *source, int type)
 {
@@ -591,13 +612,14 @@ ffi_call_int (ffi_cif *cif, void (*fn)(void), void *orig_rvalue,
   frame = stack + stack_bytes;
   rvalue = (rsize ? frame + 32 : orig_rvalue);
 
-  arg_init (&state);
+  arg_init (&state, stack_bytes);
   for (i = 0, nargs = cif->nargs; i < nargs; i++)
     {
       ffi_type *ty = cif->arg_types[i];
       size_t s = ty->size;
       void *a = avalue[i];
       int h, t;
+      void *dest;
 
       t = ty->type;
       switch (t)
@@ -645,8 +667,6 @@ ffi_call_int (ffi_cif *cif, void (*fn)(void), void *orig_rvalue,
  case FFI_TYPE_STRUCT:
  case FFI_TYPE_COMPLEX:
   {
-    void *dest;
-
     h = is_vfp_type (ty);
     if (h)
       {
@@ -664,9 +684,12 @@ ffi_call_int (ffi_cif *cif, void (*fn)(void), void *orig_rvalue,
     else if (s > 16)
       {
  /* If the argument is a composite type that is larger than 16
-   bytes, then the argument has been copied to memory, and
+   bytes, then the argument is copied to memory, and
    the argument is replaced by a pointer to the copy.  */
- a = &avalue[i];
+ dest = allocate_and_copy_struct_to_stack (&state, stack,
+  ty->alignment, s,
+  avalue[i]);
+ a = &dest;
  t = FFI_TYPE_POINTER;
  s = sizeof (void *);
  goto do_pointer;
@@ -835,7 +858,7 @@ ffi_closure_SYSV_inner (ffi_cif *cif,
   int i, h, nargs, flags;
   struct arg_state state;
 
-  arg_init (&state);
+  arg_init (&state, cif->bytes);
 
   for (i = 0, nargs = cif->nargs; i < nargs; i++)
     {
--
2.14.1


--
Andreas Schwab, SUSE Labs, [hidden email]
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."