amdgcn: Add instruction patterns for conditional min/max operations

gcc/ChangeLog:

	* config/gcn/gcn-valu.md (<expander><mode>3_exec): Add patterns for
	{s|u}{max|min} in QI, HI and DI modes.
	(<expander><mode>3): Add pattern for {s|u}{max|min} in DI mode.
	(cond_<fexpander><mode>): Add pattern for cond_f{max|min}.
	(cond_<expander><mode>): Add pattern for cond_{s|u}{max|min}.
	* config/gcn/gcn.cc (gcn_spill_class): Allow the exec register to be
	saved in SGPRs.

gcc/testsuite/ChangeLog:

	* gcc.target/gcn/cond_fmaxnm_1.c: New test.
	* gcc.target/gcn/cond_fmaxnm_1_run.c: New test.
	* gcc.target/gcn/cond_fmaxnm_2.c: New test.
	* gcc.target/gcn/cond_fmaxnm_2_run.c: New test.
	* gcc.target/gcn/cond_fmaxnm_3.c: New test.
	* gcc.target/gcn/cond_fmaxnm_3_run.c: New test.
	* gcc.target/gcn/cond_fmaxnm_4.c: New test.
	* gcc.target/gcn/cond_fmaxnm_4_run.c: New test.
	* gcc.target/gcn/cond_fmaxnm_5.c: New test.
	* gcc.target/gcn/cond_fmaxnm_5_run.c: New test.
	* gcc.target/gcn/cond_fmaxnm_6.c: New test.
	* gcc.target/gcn/cond_fmaxnm_6_run.c: New test.
	* gcc.target/gcn/cond_fmaxnm_7.c: New test.
	* gcc.target/gcn/cond_fmaxnm_7_run.c: New test.
	* gcc.target/gcn/cond_fmaxnm_8.c: New test.
	* gcc.target/gcn/cond_fmaxnm_8_run.c: New test.
	* gcc.target/gcn/cond_fminnm_1.c: New test.
	* gcc.target/gcn/cond_fminnm_1_run.c: New test.
	* gcc.target/gcn/cond_fminnm_2.c: New test.
	* gcc.target/gcn/cond_fminnm_2_run.c: New test.
	* gcc.target/gcn/cond_fminnm_3.c: New test.
	* gcc.target/gcn/cond_fminnm_3_run.c: New test.
	* gcc.target/gcn/cond_fminnm_4.c: New test.
	* gcc.target/gcn/cond_fminnm_4_run.c: New test.
	* gcc.target/gcn/cond_fminnm_5.c: New test.
	* gcc.target/gcn/cond_fminnm_5_run.c: New test.
	* gcc.target/gcn/cond_fminnm_6.c: New test.
	* gcc.target/gcn/cond_fminnm_6_run.c: New test.
	* gcc.target/gcn/cond_fminnm_7.c: New test.
	* gcc.target/gcn/cond_fminnm_7_run.c: New test.
	* gcc.target/gcn/cond_fminnm_8.c: New test.
	* gcc.target/gcn/cond_fminnm_8_run.c: New test.
	* gcc.target/gcn/cond_smax_1.c: New test.
	* gcc.target/gcn/cond_smax_1_run.c: New test.
	* gcc.target/gcn/cond_smin_1.c: New test.
	* gcc.target/gcn/cond_smin_1_run.c: New test.
	* gcc.target/gcn/cond_umax_1.c: New test.
	* gcc.target/gcn/cond_umax_1_run.c: New test.
	* gcc.target/gcn/cond_umin_1.c: New test.
	* gcc.target/gcn/cond_umin_1_run.c: New test.
	* gcc.target/gcn/smax_1.c: New test.
	* gcc.target/gcn/smax_1_run.c: New test.
	* gcc.target/gcn/smin_1.c: New test.
	* gcc.target/gcn/smin_1_run.c: New test.
	* gcc.target/gcn/umax_1.c: New test.
	* gcc.target/gcn/umax_1_run.c: New test.
	* gcc.target/gcn/umin_1.c: New test.
	* gcc.target/gcn/umin_1_run.c: New test.