[ping] [RFA] Fix varargs calls for PowerPC System V ABI

[Mark Kettenis <mark.kettenis@xs4all.nl>]

Sent this one about two months ago.  Kevin is excused since I
misspelled his mail address ;-).

------- Start of forwarded message -------
Date: Sun, 19 Jun 2005 12:30:55 +0200 (CEST)
From: Mark Kettenis <kettenis@elgar.sibelius.xs4all.nl>
To: gdb-patches@sources.redhat.com
CC: kevinb@redhat.com, cagney@gnu.org
Subject: [ping] [RFA] Fix varargs calls for PowerPC System V ABI

The patch below fixes

FAIL: gdb.base/varargs.exp: print find_max_double(5,1.0,17.0,2.0,3.0,4.0)

on my OpenBSD/macppc system.  Rather than having a (possibly) fragile
check for vararg-ness, it always sets the bit in the condition
register.  Normal functions shouldn't care for it, and indeed the way
we did these calls in the past, the condition register might be set to
anything.

OK?

Mark


Index: ChangeLog
from  Mark Kettenis  <kettenis@gnu.org>

	* ppc-sysv-tdep.c (ppc_sysv_abi_push_dummy_call): Set condition
	register appropriately for varargs functions.

Index: ppc-sysv-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/ppc-sysv-tdep.c,v
retrieving revision 1.29
diff -u -p -r1.29 ppc-sysv-tdep.c
--- ppc-sysv-tdep.c 25 May 2005 03:12:13 -0000 1.29
+++ ppc-sysv-tdep.c 19 Jun 2005 10:24:55 -0000
@@ -295,6 +295,24 @@ ppc_sysv_abi_push_dummy_call (struct gdb
 	  /* Ensure that the stack is still 16 byte aligned.  */
 	  sp = align_down (sp, 16);
 	}
+
+      /* The psABI says that "A caller of a function that takes a
+	 variable argument list shall set condition register bit 6 to
+	 1 if it passes one or more arguments in the floating-point
+	 registers. It is strongly recommended that the caller set the
+	 bit to 0 otherwise..."  Doing this for normal functions too
+	 shouldn't hurt.  */
+      if (write_pass)
+	{
+	  ULONGEST cr;
+
+	  regcache_cooked_read_unsigned (regcache, tdep->ppc_cr_regnum, &cr);
+	  if (freg > 1)
+	    cr |= 0x02000000;
+	  else
+	    cr &= ~0x02000000;
+	  regcache_cooked_write_unsigned (regcache, tdep->ppc_cr_regnum, cr);
+	}
     }
 
   /* Update %sp.   */