MSP430: Don't save all callee-saved regs in non-leaf interrupt functions

MSP430: Don't save all callee-saved regs in non-leaf interrupt functions

Previously, all callee-saved regs would unconditionally be saved
in interrupt functions that call another function.

2019-07-22  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* config/msp430/msp430.c (msp430_preserve_reg_p): Don't save
	callee-saved regs R4->R10 in an interrupt function that calls another
	function.

2019-07-22  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* gcc.target/msp430/isr-push-pop-main.c: New test.
	* gcc.target/msp430/isr-push-pop-isr-430.c: Likewise.
	* gcc.target/msp430/isr-push-pop-isr-430x.c: Likewise.
	* gcc.target/msp430/isr-push-pop-leaf-isr-430.c: Likewise.
	* gcc.target/msp430/isr-push-pop-leaf-isr-430x.c: Likewise.

From-SVN: r273702