define_split doesn't work since pass_combine assume it produces at
most 2 insns after split, but here it produces 3 since we need to move
const0_rtx (V2HImode) to reg. The move insn can be eliminated later.
gcc/ChangeLog:
PR target/112276
* config/i386/mmx.md (*mmx_pblendvb_v8qi_1): Change
define_split to define_insn_and_split to handle
immediate_operand for comparison.
(*mmx_pblendvb_v8qi_2): Ditto.
(*mmx_pblendvb_<mode>_1): Ditto.
(*mmx_pblendvb_v4qi_2): Ditto.
(<code><mode>3): Remove define_split after it.
(<code>v8qi3): Ditto.
(<code><mode>3): Ditto.
(<ode>v2hi3): Ditto.
gcc/testsuite/ChangeLog:
* g++.target/i386/part-vect-vcondhf.C: Adjust testcase.
* gcc.target/i386/pr112276.c: New test.