--- valgrind/coregrind/m_stacktrace.c.jj	2012-08-05 18:04:16.000000000 +0200

+++ valgrind/coregrind/m_stacktrace.c	2012-08-10 12:13:46.069797051 +0200

@@ -149,11 +149,23 @@ UInt VG_(get_StackTrace_wrk) ( ThreadId

       /* Try to derive a new (ip,sp,fp) triple from the current

          set. */

-      /* On x86, first try the old-fashioned method of following the

-         %ebp-chain.  Code which doesn't use this (that is, compiled

-         with -fomit-frame-pointer) is not ABI compliant and so

-         relatively rare.  Besides, trying the CFI first almost always

-         fails, and is expensive. */

+      /* On x86 GCC 4.6 and later now defaults to -fomit-frame-pointer

+         together with emitting unwind info (-fasynchronous-unwind-tables).

+         So, try CF info first.  */

+      if ( VG_(use_CF_info)( &uregs, fp_min, fp_max ) ) {

+         if (0 == uregs.xip || 1 == uregs.xip) break;

+         if (sps) sps[i] = uregs.xsp;

+         if (fps) fps[i] = uregs.xbp;

+         ips[i++] = uregs.xip - 1; /* -1: refer to calling insn, not the RA */

+         if (debug)

+            VG_(printf)("     ipsC[%d]=0x%08lx\n", i-1, ips[i-1]);

+         uregs.xip = uregs.xip - 1;

+            /* as per comment at the head of this loop */

+         continue;

+      }

+

+      /* And only then the old-fashioned method of following the

+         %ebp-chain.  */

       /* Deal with frames resulting from functions which begin "pushl%

          ebp ; movl %esp, %ebp" which is the ABI-mandated preamble. */

       if (fp_min <= uregs.xbp &&

@@ -179,20 +191,6 @@ UInt VG_(get_StackTrace_wrk) ( ThreadId

          uregs.xip = uregs.xip - 1;

             /* as per comment at the head of this loop */

          continue;

-      }

-

-      /* That didn't work out, so see if there is any CF info to hand

-         which can be used. */

-      if ( VG_(use_CF_info)( &uregs, fp_min, fp_max ) ) {

-         if (0 == uregs.xip || 1 == uregs.xip) break;

-         if (sps) sps[i] = uregs.xsp;

-         if (fps) fps[i] = uregs.xbp;

-         ips[i++] = uregs.xip - 1; /* -1: refer to calling insn, not the RA */

-         if (debug)

-            VG_(printf)("     ipsC[%d]=0x%08lx\n", i-1, ips[i-1]);

-         uregs.xip = uregs.xip - 1;

-            /* as per comment at the head of this loop */

-         continue;

       }

       /* And, similarly, try for MSVC FPO unwind info. */