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[PATCH] PR 18096: Diagnose stack frame overflow in rs6000.c
- From: Roger Sayle <roger at eyesopen dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: David Edelsohn <dje at watson dot ibm dot com>
- Date: Sat, 30 Oct 2004 10:38:20 -0600 (MDT)
- Subject: [PATCH] PR 18096: Diagnose stack frame overflow in rs6000.c
The following patch is my proposed fix to PR middle-end/18096 which is
an ICE on valid, attempting to compile a function with a ridiculously
large stack frame. On many platforms we just silently generate incorrect
code, but for the rs6000 backend, we generate an unrecognizable insn.
My proposed fix is to tweak "rs6000_emit_allocate_stack" to correctly
use gen_int_mode rather than GEN_INT to correct the problem, but then
to clear my conscience I also check for such an overflow, and generate
a diagnostic warning, and emit a trap instruction, such that if the
function is ever called at run-time we abort rather than introduce
undefined behaviour.
I'm not sure if this sort of stack frame overflow can be detected and
diagnosed in the middle-end, as frame calculations (including padding,
alignment etc...) are typically target specific. In this case, using
gen_int_mode is clearly the correct thing to ensure that CONST_INTs
are correctly extended for their modes.
The following patch has been tested on powerpc-unknown-linux-gnu with
a full "make bootstrap", all default languages, and regression tested
with a top-level "make -k check" with no new failures.
Ok for mainline? I'd also appreciate it if someone could annotate the
bugzilla PR to confirm this isn't a regression from 2.95 or 3.2. TIA.
2004-10-30 Roger Sayle <roger@eyesopen.com>
PR middle-end/18096
* config/rs6000/rs6000.c (rs6000_emit_allocate_stack): Check that
the stack adjustment, "size", is valid for Pmode. If the stack
frame is too large, generate a trap insn and issue a warning.
* gcc.dg/PR18096-1.c: New test case.
Index: rs6000.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/rs6000/rs6000.c,v
retrieving revision 1.732
diff -c -3 -p -r1.732 rs6000.c
*** rs6000.c 28 Oct 2004 22:32:41 -0000 1.732
--- rs6000.c 29 Oct 2004 22:48:18 -0000
*************** rs6000_emit_allocate_stack (HOST_WIDE_IN
*** 13111,13117 ****
rtx insn;
rtx stack_reg = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
rtx tmp_reg = gen_rtx_REG (Pmode, 0);
! rtx todec = GEN_INT (-size);
if (current_function_limit_stack)
{
--- 13111,13124 ----
rtx insn;
rtx stack_reg = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
rtx tmp_reg = gen_rtx_REG (Pmode, 0);
! rtx todec = gen_int_mode (-size, Pmode);
!
! if (INTVAL (todec) != -size)
! {
! warning("stack frame too large");
! emit_insn (gen_trap ());
! return;
! }
if (current_function_limit_stack)
{
/* PR middle-end/18096 */
/* { dg-do compile { target powerpc-*-* } } */
/* { dg-options "-O2" } */
void f(char*);
void mkcatdefs(char *fname)
{
char line [2147483647];
f(line);
} /* { dg-warning "stack frame too large" "stack frame too large" } */
Roger
--
Roger Sayle, E-mail: roger@eyesopen.com
OpenEye Scientific Software, WWW: http://www.eyesopen.com/
Suite 1107, 3600 Cerrillos Road, Tel: (+1) 505-473-7385
Santa Fe, New Mexico, 87507. Fax: (+1) 505-473-0833