[ARM][PR target/84826] Fix ICE in extract_insn, at recog.c:2304 on

[ARM][PR target/84826] Fix ICE in extract_insn, at recog.c:2304 on
arm-linux-gnueabi

The ICE in the bug report was happening because the macro
USE_RETURN_INSN (FALSE) was returning different values at different points
in the compilation. This was internally occurring because the function
arm_compute_static_chain_stack_bytes () which was dependent on
arm_r3_live_at_start_p () was giving a different value after the cond_exec
instructions were created in ce3 causing the liveness of r3 to escape up
to the start block.

The function arm_compute_static_chain_stack_bytes () should really only
compute the value once duringepilogue/prologue stage. This pass introduces
a new member 'static_chain_stack_bytes' to the target definition of the
struct machine_function which gets calculated in expand_prologue and is the
value that is returned by arm_compute_static_chain_stack_bytes () beyond that.

ChangeLog entries:

*** gcc/ChangeLog ***

2018-03-22  Sudakshina Das  <sudi.das@arm.com>

	PR target/84826
	* config/arm/arm.h (machine_function): Add static_chain_stack_bytes.
	* config/arm/arm.c (arm_compute_static_chain_stack_bytes): Avoid
	re-computing once computed.
	(arm_expand_prologue): Compute machine->static_chain_stack_bytes.
	(arm_init_machine_status): Initialize
	machine->static_chain_stack_bytes.

*** gcc/testsuite/ChangeLog ***

2018-03-22  Sudakshina Das  <sudi.das@arm.com>

	PR target/84826
	* gcc.target/arm/pr84826.c: New test.

From-SVN: r258777