This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: PATCH: PR target/34001: Incorrect x86 fastcall behavior
On Thu, Nov 15, 2007 at 08:51:02PM -0800, H.J. Lu wrote:
> On Fri, Nov 16, 2007 at 12:35:47PM +0800, Ye, Joey wrote:
> > HJ,
> >
> > You patch has a minor problem that fastcall will pass non-scalar integer parameter in EAX/ECX/EDX, which is still imcompatible to MS fastcall. MSVC pass parameter on stack unless it is scalar integer less equal to 32 bits.
> >
> > With this patch GCC fastcall passes first parameter in EAX when it is not a scalar integer less equal to 32 bits. Check following example and review the patch fixing it:
> >
> > Here is a patch to fix it:
> > Index: gcc/config/i386/i386.c
> > ===================================================================
> > --- gcc/config/i386/i386.c (revision 129880)
> > +++ gcc/config/i386/i386.c (working copy)
> > @@ -4229,9 +4229,12 @@
> > int regno = cum->regno;
> >
> > /* Fastcall allocates the first two DWORD (SImode) or
> > - smaller arguments to ECX and EDX. */
> > + smaller arguments to ECX and EDX if it isn't an
> > + aggregate type . */
> > if (cum->fastcall)
> > {
> > + if (type && AGGREGATE_TYPE_P (type))
> > + break;
> > if (mode == BLKmode || mode == DImode)
> > break;
> >
>
> Yes, this version is correct. Thanks.
>
>
Here is an equivalent patch.
H.J.
----
2007-11-15 H.J. Lu <hongjiu.lu@intel.com>
Joey Ye <joey.ye@intel.com>
PR target/34001
* config/i386/i386.c (function_arg_32): Don't pass aggregate
arguments in ECX/EDX for fastcall.
--- gcc/config/i386/i386.c.fastcall 2007-11-16 05:41:46.000000000 -0800
+++ gcc/config/i386/i386.c 2007-11-16 05:46:43.000000000 -0800
@@ -4257,10 +4257,12 @@ function_arg_32 (CUMULATIVE_ARGS *cum, e
int regno = cum->regno;
/* Fastcall allocates the first two DWORD (SImode) or
- smaller arguments to ECX and EDX. */
+ smaller arguments to ECX and EDX if it isn't an
+ aggregate type . */
if (cum->fastcall)
{
- if (mode == BLKmode || mode == DImode)
+ if (mode == BLKmode || mode == DImode
+ || (type && AGGREGATE_TYPE_P (type)))
break;
/* ECX not EAX is the first allocated register. */