[ARM] Fix PR middle-end/65958

[Eric Botcazou]

> More comments inline.

Revised version attached, which addresses all your comments and in particular 
removes the

+#if PROBE_INTERVAL > 4096
+#error Cannot use indexed addressing mode for stack probing
+#endif

compile-time assertion.  It generates the same code for PROBE_INTERVAL == 4096 
as before and it generates code that can be assembled for 8192.

Tested on Aarch64/Linux, OK for the mainline?


2015-11-16  Tristan Gingold  <gingold@adacore.com>
            Eric Botcazou  <ebotcazou@adacore.com>

        PR middle-end/65958
        * config/aarch64/aarch64-protos.h (aarch64_output_probe_stack-range):
        Declare.
        * config/aarch64/aarch64.md: Declare UNSPECV_BLOCKAGE and
        UNSPEC_PROBE_STACK_RANGE.
        (blockage): New instruction.
        (probe_stack_range): Likewise.
        * config/aarch64/aarch64.c (aarch64_emit_probe_stack_range): New
        function.
        (aarch64_output_probe_stack_range): Likewise.
        (aarch64_expand_prologue): Invoke aarch64_emit_probe_stack_range if
        static builtin stack checking is enabled.
        * config/aarch64/aarch64-linux.h (STACK_CHECK_STATIC_BUILTIN):
        Define.


2015-11-16  Eric Botcazou  <ebotcazou@adacore.com>

        * gcc.target/aarch64/stack-checking.c: New test.

-- 
Eric Botcazou
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