[PATCH, GCC/ARM, 3/10] Save/restore FPCXTNS in nsentry functions

[PATCH, GCC/ARM, 3/10] Save/restore FPCXTNS in nsentry functions

This patch consists mainly of creating 2 new instruction patterns to
push and pop special FP registers via vldm and vstr and using them in
prologue and epilogue. The patterns are defined as push/pop with an
unspecified operation on the memory accessed, with an unspecified
constant indicating what special FP register is being saved/restored.

Other aspects of the patch include:
  * defining the set of special registers that can be saved/restored and
    their name
  * reserving space in the stack frames for these push/pop
  * preventing return via pop
  * guarding the clearing of FPSCR to target architecture not having
    Armv8.1-M Mainline instructions.

*** gcc/ChangeLog ***

2020-01-16  Mihail-Calin Ionescu  <mihail.ionescu@arm.com>
2020-01-16  Thomas Preud'homme  <thomas.preudhomme@arm.com>

	* config/arm/arm.c (fp_sysreg_names): Declare and define.
	(use_return_insn): Also return false for Armv8.1-M Mainline.
	(output_return_instruction): Skip FPSCR clearing if Armv8.1-M
	Mainline instructions are available.
	(arm_compute_frame_layout): Allocate space in frame for FPCXTNS
	when targeting Armv8.1-M Mainline Security Extensions.
	(arm_expand_prologue): Save FPCXTNS if this is an Armv8.1-M
	Mainline entry function.
	(cmse_nonsecure_entry_clear_before_return): Clear IP and r4 if
	targeting Armv8.1-M Mainline or successor.
	(arm_expand_epilogue): Fix indentation of caller-saved register
	clearing.  Restore FPCXTNS if this is an Armv8.1-M Mainline
	entry function.
	* config/arm/arm.h (TARGET_HAVE_FP_CMSE): New macro.
	(FP_SYSREGS): Likewise.
	(enum vfp_sysregs_encoding): Define enum.
	(fp_sysreg_names): Declare.
	* config/arm/unspecs.md (VUNSPEC_VSTR_VLDR): New volatile unspec.
	* config/arm/vfp.md (push_fpsysreg_insn): New define_insn.
	(pop_fpsysreg_insn): Likewise.

*** gcc/testsuite/Changelog ***

2020-01-16  Mihail-Calin Ionescu  <mihail.ionescu@arm.com>
2020-01-16  Thomas Preud'homme  <thomas.preudhomme@arm.com>

	* gcc.target/arm/cmse/bitfield-1.c: add checks for VSTR and VLDR.
	* gcc.target/arm/cmse/bitfield-2.c: Likewise.
	* gcc.target/arm/cmse/bitfield-3.c: Likewise.
	* gcc.target/arm/cmse/cmse-1.c: Likewise.
	* gcc.target/arm/cmse/struct-1.c: Likewise.
	* gcc.target/arm/cmse/cmse.exp: Run existing Armv8-M Mainline tests
	from mainline/8m subdirectory and new Armv8.1-M Mainline tests from
	mainline/8_1m subdirectory.
	* gcc.target/arm/cmse/mainline/bitfield-4.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/bitfield-4.c: This.
	* gcc.target/arm/cmse/mainline/bitfield-5.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/bitfield-5.c: This.
	* gcc.target/arm/cmse/mainline/bitfield-6.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/bitfield-6.c: This.
	* gcc.target/arm/cmse/mainline/bitfield-7.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/bitfield-7.c: This.
	* gcc.target/arm/cmse/mainline/bitfield-8.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/bitfield-8.c: This.
	* gcc.target/arm/cmse/mainline/bitfield-9.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/bitfield-9.c: This.
	* gcc.target/arm/cmse/mainline/bitfield-and-union-1.c: Move and rename
	into ...
	* gcc.target/arm/cmse/mainline/8m/bitfield-and-union.c: This.
	* gcc.target/arm/cmse/mainline/hard-sp/cmse-13.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard-sp/cmse-13.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/hard-sp/cmse-5.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard-sp/cmse-5.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/hard-sp/cmse-7.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard-sp/cmse-7.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/hard-sp/cmse-8.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard-sp/cmse-8.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/hard/cmse-13.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard/cmse-13.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/hard/cmse-5.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard/cmse-5.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/hard/cmse-7.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard/cmse-7.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/hard/cmse-8.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/hard/cmse-8.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/soft/cmse-13.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/soft/cmse-13.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/soft/cmse-5.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/soft/cmse-5.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/soft/cmse-7.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/soft/cmse-7.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/soft/cmse-8.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/soft/cmse-8.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/softfp-sp/cmse-5.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/softfp-sp/cmse-5.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/softfp-sp/cmse-7.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/softfp-sp/cmse-7.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/softfp-sp/cmse-8.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/softfp-sp/cmse-8.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/softfp/cmse-13.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/softfp/cmse-13.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/softfp/cmse-5.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/softfp/cmse-5.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/softfp/cmse-7.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/softfp/cmse-7.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/softfp/cmse-8.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/softfp/cmse-8.c: This.  Clean up
	dg-skip-if directive for float ABI.
	* gcc.target/arm/cmse/mainline/union-1.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/union-1.c: This.
	* gcc.target/arm/cmse/mainline/union-2.c: Move into ...
	* gcc.target/arm/cmse/mainline/8m/union-2.c: This.
	* gcc.target/arm/cmse/mainline/8_1m/bitfield-4.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/bitfield-5.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/bitfield-6.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/bitfield-7.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/bitfield-8.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/bitfield-9.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/bitfield-and-union.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard-sp/cmse-13.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard-sp/cmse-5.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard-sp/cmse-7.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard-sp/cmse-8.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-13.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-5.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-7.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-8.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/soft/cmse-13.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/soft/cmse-5.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/soft/cmse-7.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/soft/cmse-8.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/softfp-sp/cmse-5.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/softfp-sp/cmse-7.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/softfp-sp/cmse-8.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/softfp/cmse-13.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/softfp/cmse-5.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/softfp/cmse-7.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/softfp/cmse-8.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/union-1.c: New file.
	* gcc.target/arm/cmse/mainline/8_1m/union-2.c: New file.
	* lib/target-supports.exp (check_effective_target_arm_cmse_clear_ok):
	New procedure.