On Saturday 23 April 2011 09:35:38 Uros Bizjak wrote:
> Index: i386.c
> ===================================================================
> --- i386.c (revision 172866)
> +++ i386.c (working copy)
> @@ -10149,7 +10149,7 @@ ix86_adjust_stack_and_probe (const HOST_
> /* Even if the stack pointer isn't the CFA register, we need to
> correctly describe the adjustments made to it, in particular differentiate
> the frame-related ones from the frame-unrelated ones. */
> - if (size > 0)
> + if (size != 0)
> {
> rtx expr = gen_rtx_SEQUENCE (VOIDmode, rtvec_alloc (2));
> XVECEXP (expr, 0, 0)
Probing for a negative size doesn't make much sense; we shouldn't be there if
the size to allocate is negative. Is that really intended? The code without
stack checking is:
pushq %rbp
.LCFI0:
movq %rsp, %rbp
.LCFI1:
andq $-32, %rsp
addq $16, %rsp
which looks weird. If this is nevertheless correct, then the fix for the
problem is attached. Tested on x86_64-suse-linux.
PR target/48723
* config/i386/i386.c (ix86_expand_prologue): Do not probe the stack
for -fstack-check if the size to allocate is negative.
--
Eric Botcazou
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 173209)
+++ config/i386/i386.c (working copy)
@@ -10619,8 +10619,8 @@ ix86_expand_prologue (void)
}
/* The stack has already been decremented by the instruction calling us
- so we need to probe unconditionally to preserve the protection area. */
- if (flag_stack_check == STATIC_BUILTIN_STACK_CHECK)
+ so probe if the size is non-negative to preserve the protection area. */
+ if (allocate >= 0 && flag_stack_check == STATIC_BUILTIN_STACK_CHECK)
{
/* We expect the registers to be saved when probes are used. */
gcc_assert (int_registers_saved);
