Re: Fix PR41718, ICE when compiling a large testcase

[Richard Guenther <richard dot guenther at gmail dot com>]

On Fri, Nov 13, 2009 at 10:06 AM, Bernd Schmidt <bernds_cb1@t-online.de> wrote:
> As noted in the PR, there's an integer overflow that can trigger with
> very large input files. ?The patch below does two things: it doubles the
> maximum size of the array by exchanging the order of multiplication and
> division in the overflowing expression. ?It also tries to detect
> overflows and give a fatal_error message rather than just an ICE.
>
> The former is enough to make the testcase compile on my 32 bit
> i686-linux system.
>
> Bootstrap in progress, ok if no regressions?

Ok.

Thanks,
Richard.

>
> Bernd
> --
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>
> ? ? ? ?* cfgexpand (n_stack_vars_conflict): New static variable.
> ? ? ? ?(triangular_index): Reduce likelyhood of overflow by performing
> ? ? ? ?the division before the multiplication.
> ? ? ? ?(resize_stack_vars_conflict): Call fatal_error if overflow
> ? ? ? ?occurred in triangular_index. ?Update n_stack_vars_conflict.
>
> Index: cfgexpand.c
> ===================================================================
> --- cfgexpand.c (revision 154120)
> +++ cfgexpand.c (working copy)
> @@ -213,6 +213,7 @@ static size_t *stack_vars_sorted;
> ? ?is lower triangular. ?*/
> ?static bool *stack_vars_conflict;
> ?static size_t stack_vars_conflict_alloc;
> +static size_t n_stack_vars_conflict;
>
> ?/* The phase of the stack frame. ?This is the known misalignment of
> ? ?virtual_stack_vars_rtx from PREFERRED_STACK_BOUNDARY. ?That is,
> @@ -331,7 +332,11 @@ triangular_index (size_t i, size_t j)
> ? ? ? size_t t;
> ? ? ? t = i, i = j, j = t;
> ? ? }
> - ?return (i * (i + 1)) / 2 + j;
> +
> + ?if (i & 1)
> + ? ?return ((i + 1) / 2) * i + j;
> + ?else
> + ? ?return (i / 2) * (i + 1) + j;
> ?}
>
> ?/* Ensure that STACK_VARS_CONFLICT is large enough for N objects. ?*/
> @@ -342,12 +347,17 @@ resize_stack_vars_conflict (size_t n)
> ? size_t size = triangular_index (n-1, n-1) + 1;
>
> ? if (size <= stack_vars_conflict_alloc)
> - ? ?return;
> + ? ?{
> + ? ? ?if (n > n_stack_vars_conflict)
> + ? ? ? fatal_error ("program is too large to be compiled on this machine");
> + ? ? ?return;
> + ? ?}
>
> ? stack_vars_conflict = XRESIZEVEC (bool, stack_vars_conflict, size);
> ? memset (stack_vars_conflict + stack_vars_conflict_alloc, 0,
> ? ? ? ? ?(size - stack_vars_conflict_alloc) * sizeof (bool));
> ? stack_vars_conflict_alloc = size;
> + ?n_stack_vars_conflict = n;
> ?}
>
> ?/* Make the decls associated with luid's X and Y conflict. ?*/
>
>