tcg-arm: Simplify logic in detecting the ARM ISA in use

GCC 4.8 defines a handy __ARM_ARCH symbol that we can use, which
will make us nicely forward compatible with ARMv8 AArch32.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Use AT_PLATFORM to detect the host ISA

With this we can generate armv7 insns even when the OS compiles for a
lower common denominator.  The macros are arranged so that when we do
compile for a given ISA, all of the runtime checks for that ISA are
optimized away.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Fix high_pc fields in .debug_info

I don't think the debugger actually looks at this for anything,
using the correct .debug_frame contents, but might as well get
it all correct.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Move the CIE and FDE header definitions to common code

These will necessarily be the same layout for all hosts.  This limits
the amount of boilerplate required to implement jit debug for a host.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-i386: Use QEMU_BUILD_BUG_ON instead of assert for frame size

We can check the condition at compile time, rather than run time.

Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Implement tcg_register_jit

Allows unwinding past the code_gen_buffer.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>