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Re: [libitm] Remove variadic argument of _ITM_beginTransaction from libitm.h
- From: Patrick Marlier <patrick dot marlier at gmail dot com>
- To: Torvald Riegel <triegel at redhat dot com>
- Cc: Richard Henderson <rth at redhat dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>, Aldy Hernandez <aldyh at redhat dot com>
- Date: Thu, 29 Dec 2011 11:52:26 -0500
- Subject: Re: [libitm] Remove variadic argument of _ITM_beginTransaction from libitm.h
- References: <4EFBCA88.7060801@gmail.com> <1325159942.7636.23.camel@triegel.csb>
On 12/29/2011 06:59 AM, Torvald Riegel wrote:
On Wed, 2011-12-28 at 21:03 -0500, Patrick Marlier wrote:
With i386, the regparm(2) is not taken into account when there is a
variadic function. All parameters are in the stack.
Since this variable argument is never used removing it is not a problem.
The ABI specifies beginTransaction as a variadic function, however.
Even though we don't use that currently, there were reasons why we added
that in the first place (e.g., to be able to add additional bits later
on, including support for more codepaths).
I am pretty sure this is a bug in the ABI. AFAIU in 32bits, a function
cannot be variadic and satisfy regparm(2).
Is there another way we can fix this? Or is regparm in general
undefined for variadic functions?
in i386.c (init_cumulative_args):
...
if (!TARGET_64BIT)
{
/* If there are variable arguments, then we won't pass anything
in registers in 32-bit mode. */
if (stdarg_p (fntype))
{
cum->nregs = 0;
cum->sse_nregs = 0;
cum->mmx_nregs = 0;
cum->warn_avx = 0;
cum->warn_sse = 0;
cum->warn_mmx = 0;
return;
}
So I don't really see another way to fix it.
Maybe Master Aldy or Master Richard?
Patrick.