This patch adds a new pattern for the VSCCLRM instruction.
cmse_clear_registers () is then modified to use the new VSCCLRM
instruction when targeting Armv8.1-M Mainline, thus, making the Armv8-M
register clearing code specific to Armv8-M.

Since the VSCCLRM instruction mandates VPR in the register list, the
pattern is encoded with a parallel which only requires an unspecified
VUNSPEC_CLRM_VPR constant modelling the APSR clearing. Other expression
in the parallel are expected to be set expression for clearing the VFP
registers.

*** 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-protos.h (clear_operation_p): Adapt prototype.
	* config/arm/arm.c (clear_operation_p): Extend to be able to check a
	clear_vfp_multiple pattern based on a new vfp parameter.
	(cmse_clear_registers): Generate VSCCLRM to clear VFP registers when
	targeting Armv8.1-M Mainline.
	(cmse_nonsecure_entry_clear_before_return): Clear VFP registers
	unconditionally when targeting Armv8.1-M Mainline architecture.  Check
	whether VFP registers are available before looking call_used_regs for a
	VFP register.
	* config/arm/predicates.md (clear_multiple_operation): Adapt to change
	of prototype of clear_operation_p.
	(clear_vfp_multiple_operation): New predicate.
	* config/arm/unspecs.md (VUNSPEC_VSCCLRM_VPR): New volatile unspec.
	* config/arm/vfp.md (clear_vfp_multiple): New define_insn.

*** 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 check for VSCCLRM.
	* 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/mainline/8_1m/hard-sp/cmse-13.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/hard-sp/cmse-5.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/hard-sp/cmse-7.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/hard-sp/cmse-8.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-13.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-5.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-7.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/hard/cmse-8.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/soft/cmse-5.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/softfp-sp/cmse-5.c: Likewise.
	* gcc.target/arm/cmse/mainline/8_1m/softfp/cmse-5.c: Likewise.