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explow.c (optimize_save_area_alloca): New function for targets where SETJMP_VIA_SAVE_AREA is true. 

* explow.c (optimize_save_area_alloca): New function for targets
        where SETJMP_VIA_SAVE_AREA is true.
        (allocate_dynamic_stack_space): On SETJMP_VIA_SAVE_AREA targets,
        compute the amount of stack space needed should we find later that
        setjmp is never called by this function, stuff rtl for this inside
        a REG_NOTE of the final SET of stack_pointer_rtx.
        * toplev.c (rest_of_compilation): If SETJMP_VIA_SAVE_AREA and
        current_function_calls_alloca, call optimize_save_area_alloca.
CVS ----------------------------------------------------------------------

From-SVN: r17402
This commit is contained in:
David S. Miller 1998-01-17 22:39:10 +00:00 committed by Jeff Law
parent ca097615db
commit c9ec4f99bc
3 changed files with 150 additions and 0 deletions
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11
gcc/ChangeLog
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@ -1,3 +1,14 @@
Sat Jan 17 23:41:36 1998 David S. Miller <davem@tanya.rutgers.edu>
* explow.c (optimize_save_area_alloca): New function for targets
where SETJMP_VIA_SAVE_AREA is true.
(allocate_dynamic_stack_space): On SETJMP_VIA_SAVE_AREA targets,
compute the amount of stack space needed should we find later that
setjmp is never called by this function, stuff rtl for this inside
a REG_NOTE of the final SET of stack_pointer_rtx.
* toplev.c (rest_of_compilation): If SETJMP_VIA_SAVE_AREA and
current_function_calls_alloca, call optimize_save_area_alloca.
Sat Jan 17 23:22:59 1998 John Wehle (john@feith.com)
* i386.md: Remove redundant integer push patterns.

133
gcc/explow.c
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@ -1004,6 +1004,86 @@ emit_stack_restore (save_level, sa, after)
emit_insn (fcn (stack_pointer_rtx, sa));
}
#ifdef SETJMP_VIA_SAVE_AREA
/* Optimize RTL generated by allocate_dynamic_stack_space for targets
where SETJMP_VIA_SAVE_AREA is true. The problem is that on these
platforms, the dynamic stack space used can corrupt the original
frame, thus causing a crash if a longjmp unwinds to it. */
void
optimize_save_area_alloca (insns)
rtx insns;
{
rtx insn;
for (insn = insns; insn; insn = NEXT_INSN(insn))
{
rtx note;
if (GET_CODE (insn) != INSN)
continue;
for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
{
if (REG_NOTE_KIND (note) != REG_SAVE_AREA)
continue;
if (!current_function_calls_setjmp)
{
rtx pat = PATTERN (insn);
/* If we do not see the note in a pattern matching
these precise characteristics, we did something
entirely wrong in allocate_dynamic_stack_space.
Note, one way this could happen if if SETJMP_VIA_SAVE_AREA
was defined on a machine where stacks grow towards higher
addresses.
Right now only supported port with stack that grow upward
is the HPPA and it does not define SETJMP_VIA_SAVE_AREA. */
if (GET_CODE (pat) != SET
|| SET_DEST (pat) != stack_pointer_rtx
|| GET_CODE (SET_SRC (pat)) != MINUS
|| XEXP (SET_SRC (pat), 0) != stack_pointer_rtx)
abort ();
/* This will now be transformed into a (set REG REG)
so we can just blow away all the other notes. */
XEXP (SET_SRC (pat), 1) = XEXP (note, 0);
REG_NOTES (insn) = NULL_RTX;
}
else
{
/* setjmp was called, we must remove the REG_SAVE_AREA
note so that later passes do not get confused by its
presence. */
if (note == REG_NOTES (insn))
{
REG_NOTES (insn) = XEXP (note, 1);
}
else
{
rtx srch;
for (srch = REG_NOTES (insn); srch; srch = XEXP (srch, 1))
if (XEXP (srch, 1) == note)
break;
if (srch == NULL_RTX)
abort();
XEXP (srch, 1) = XEXP (note, 1);
}
}
/* Once we've seen the note of interest, we need not look at
the rest of them. */
break;
}
}
}
#endif /* SETJMP_VIA_SAVE_AREA */
/* Return an rtx representing the address of an area of memory dynamically
pushed on the stack. This region of memory is always aligned to
a multiple of BIGGEST_ALIGNMENT.
@ -1021,6 +1101,10 @@ allocate_dynamic_stack_space (size, target, known_align)
rtx target;
int known_align;
{
#ifdef SETJMP_VIA_SAVE_AREA
rtx setjmpless_size = NULL_RTX;
#endif
/* If we're asking for zero bytes, it doesn't matter what we point
to since we can't dereference it. But return a reasonable
address anyway. */
@ -1074,6 +1158,45 @@ allocate_dynamic_stack_space (size, target, known_align)
rtx dynamic_offset
= expand_binop (Pmode, sub_optab, virtual_stack_dynamic_rtx,
stack_pointer_rtx, NULL_RTX, 1, OPTAB_LIB_WIDEN);
if (!current_function_calls_setjmp)
{
int align = STACK_BOUNDARY / BITS_PER_UNIT;
/* See optimize_save_area_alloca to understand what is being
set up here. */
#if !defined(STACK_BOUNDARY) || !defined(MUST_ALIGN) || (STACK_BOUNDARY != BIGGEST_ALIGNMENT)
/* If anyone creates a target with these characteristics, let them
know that our optimization cannot work correctly in such a case. */
abort();
#endif
if (GET_CODE (size) == CONST_INT)
{
int new = INTVAL (size) / align * align;
if (INTVAL (size) != new)
setjmpless_size = GEN_INT (new);
else
setjmpless_size = size;
}
else
{
/* Since we know overflow is not possible, we avoid using
CEIL_DIV_EXPR and use TRUNC_DIV_EXPR instead. */
setjmpless_size = expand_divmod (0, TRUNC_DIV_EXPR, Pmode, size,
GEN_INT (align), NULL_RTX, 1);
setjmpless_size = expand_mult (Pmode, setjmpless_size,
GEN_INT (align), NULL_RTX, 1);
}
/* Our optimization works based upon being able to perform a simple
transformation of this RTL into a (set REG REG) so make sure things
did in fact end up in a REG. */
if (!arith_operand (setjmpless_size, Pmode))
setjmpless_size = force_reg (Pmode, setjmpless_size);
}
size = expand_binop (Pmode, add_optab, size, dynamic_offset,
NULL_RTX, 1, OPTAB_LIB_WIDEN);
}
@ -1145,6 +1268,16 @@ allocate_dynamic_stack_space (size, target, known_align)
#endif
size = convert_modes (Pmode, ptr_mode, size, 1);
anti_adjust_stack (size);
#ifdef SETJMP_VIA_SAVE_AREA
if (setjmpless_size != NULL_RTX)
{
rtx note_target = get_last_insn ();
REG_NOTES (note_target) = gen_rtx (EXPR_LIST, REG_SAVE_AREA,
setjmpless_size,
REG_NOTES (note_target));
}
#endif /* SETJMP_VIA_SAVE_AREA */
#ifdef STACK_GROWS_DOWNWARD
emit_move_insn (target, virtual_stack_dynamic_rtx);
#endif

6
gcc/toplev.c
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@ -3242,6 +3242,12 @@ rest_of_compilation (decl)
unshare_all_rtl (insns);
#ifdef SETJMP_VIA_SAVE_AREA
/* This must be performed before virutal register instantiation. */
if (current_function_calls_alloca)
optimize_save_area_alloca (insns);
#endif
/* Instantiate all virtual registers. */
instantiate_virtual_regs (current_function_decl, get_insns ());