Use architecture-specific va_list type

Previously, cproc effectively used used

	typedef struct { /* 32 bytes, 8-byte aligned */ } __builtin_va_list[1];

However, this is not quite correct for x86_64 nor aarch64, though
it was close enough for both to work in most cases.

In actuality, for x86_64 we want

	typedef struct { /* 24 bytes, 8-byte aligned */ } __builtin_va_list[1];

and for aarch64 we want

	typedef struct { /* 32 bytes, 8-byte aligned */ } __builtin_va_list;

The difference only appears when the size of va_list matters, or
when va_list is passed as a parameter. However, the former is not
often the case, and the aarch64 ABI replaces aggregate arguments
with pointers to caller-allocated memory, which is quite similar
to arrays decaying to pointers in C except that the struct is not
copied.

Additionally, riscv64 simply uses

	typedef void *__builtin_va_list;

which again has a different size and calling convention.

To fix this, make the __builtin_va_list type architecture-specific
and use architecture-specific tests for varargs-related functionality.

1 files changed, 9 insertions, 0 deletions

diff --git a/test/varargs-pass-valist+aarch64.qbe b/test/varargs-pass-valist+aarch64.qbe
new file mode 100644
index 0000000..67cef8a
--- /dev/null
+++ b/test/varargs-pass-valist+aarch64.qbe
@@ -0,0 +1,9 @@
+data $.Lap.2 = align 8 { z 32 }
+type :va_list.1 = align 8 { 32 }
+export
+function $g() {
+@start.1
+@body.2
+	call $f(:va_list.1 $.Lap.2)
+	ret
+}