gcc 3.4 regression: sched2 moving "may throw" instructions into epilogue

[Andrew Haley <aph at redhat dot com>]

g++ is compiling

------------------------------------------------------------------------
typedef struct kkclass;
typedef struct kkclass *jclass;

struct _Jv_VTable
{
  jclass clas;
};

jclass
getClass (void *p)
{
  _Jv_VTable **dt = (_Jv_VTable **) p;
  return (*dt)->clas;
}
------------------------------------------------------------------------

into 

_Z8getClassPv:
.LFB2:
        pushl   %ebp
.LCFI0:
        movl    %esp, %ebp
.LCFI1:
        movl    8(%ebp), %edx
        popl    %ebp
        movl    (%edx), %eax
        movl    (%eax), %eax
        ret
.LFE2:

where, as you can see, the code for the memory access is moved after
the stack adjustment in the epilogue.

This is despite the fact that this code was compiled with
-fnon-call-exceptions and -fno-omit-frame-pointer.

This causes a runtime failure to catch a null pointer exception.
Insns that may trap must not be move into the epilogue, because stack
unwinding when throwing exceptions will not work correctly.

g++ 3.2.2 does this, which is correct:

_Z8getClassPv:
.LFB2:
        pushl   %ebp
.LCFI0:
        movl    %esp, %ebp
.LCFI1:
        movl    8(%ebp), %eax
        movl    (%eax), %eax
        movl    (%eax), %eax
        leave
        ret
.LFE2:

The movement of the popl %ebp instruction seems to be in sched2.

Compiler options used were -O3 -fno-omit-frame-pointer -fnon-call-exceptions.

Andrew.