[Bug middle-end/65958] -fstack-check breaks alloca on architectures using generic stack checking

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65958

--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Author: ebotcazou
Date: Fri Dec  4 11:57:15 2015
New Revision: 231260

URL: https://gcc.gnu.org/viewcvs?rev=231260&root=gcc&view=rev
Log:
        PR middle-end/65958
        * gimplify.c (struct gimplify_ctx): Turn boolean fields into 1-bit
        fields, add keep_stack and reorder them.
        (gimplify_bind_expr): Save gimplify_ctxp->keep_stack on entry then
        set it to false.  Do not insert a stack save/restore pair if it has
        been set to true by the gimplification of the statements.
        Restore it to the saved value on exit if it is still false.
        (gimplify_vla_decl): Do not set gimplify_ctxp->save_stack here.
        (gimplify_call_expr) <BUILT_IN_ALLOCA[_WITH_ALIGN]>: New case.  Set
        either save_stack or keep_stack depending on CALL_ALLOCA_FOR_VAR_P.
        * doc/extend.texi (Variable Length): Document new behavior.
        * doc/generic.texi (Blocks): Document new handling of VLAs.

Added:
    trunk/gcc/testsuite/gcc.dg/vla-24.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/doc/extend.texi
    trunk/gcc/doc/generic.texi
    trunk/gcc/gimplify.c
    trunk/gcc/testsuite/ChangeLog