xtensa: Eliminate unnecessary general-purpose reg-reg moves

Register-register move instructions that can be easily seen as
unnecessary by the human eye may remain in the compiled result.
For example:

/* example */
double test(double a, double b) {
  return __builtin_copysign(a, b);
}

test:
	add.n	a3, a3, a3
	extui	a5, a5, 31, 1
	ssai	1
				;; Be in the same BB
	src	a7, a5, a3	;; Replacing the destination doesn't
				;;   violate any constraints of the
				;;   operands
				;; No CALL insns in this span
				;; Both A3 and A7 are irrelevant to
				;;   insns in this span
	mov.n	a3, a7		;; An unnecessary reg-reg move
				;; A7 is not used after this
	ret.n

The last two instructions above, excluding the return instruction,
could be done like this:

	src	a3, a5, a3

This symptom often occurs when handling DI/DFmode values with SImode
instructions.  This patch solves the above problem using peephole2
pattern.

gcc/ChangeLog:

	* config/xtensa/xtensa.md: New peephole2 pattern that eliminates
	the occurrence of general-purpose register used only once and for
	transferring intermediate value.

gcc/testsuite/ChangeLog:

	* gcc.target/xtensa/elim_GP_regmove_0.c: New test.
	* gcc.target/xtensa/elim_GP_regmove_1.c: New test.

0 files changed, 0 insertions, 0 deletions