i386: Fix and improve movhi_internal and movhf_internal some more.

i386: Fix and improve movhi_internal and movhf_internal some more.

An (*v,C) alternative can be added to movhi_internal to directly load
HImode constant 0 to xmm register. Also, V4SFmode moves can be used
for xmm->xmm moves instead of TImode moves when optimizing for size.
Fix invalid %vpinsrw insn template, which needs to duplicate %xmm
register for AVX targets.

Optimize GPR moves in movhf_internal in the same way as in movhi_internal.
Fix pinsrw and pextrw templates for AVX targets. Use sselog1
instead of sselog type.  Also, handle TARGET_SSE_PARTIAL_REG_DEPENDENCY
and TARGET_SSE_SPLIT_REGS targets.

2021-11-29  Uroš Bizjak  <ubizjak@gmail.com>

gcc/ChangeLog:

	PR target/102811
	* config/i386/i386.md (*movhi_internal): Introduce (*v,C) alternative.
	Do not allocate non-GPR registers.  Optimize xmm->xmm moves when
	optimizing for size.  Fix vpinsrw insn template.
	(*movhf_internal): Fix pinsrw and pextrw insn templates for
	AVX targets. Use sselog1 type instead of sselog.  Optimize GPR moves.
	Optimize xmm->xmm moves for TARGET_SSE_PARTIAL_REG_DEPENDENCY
	and TARGET_SSE_SPLIT_REGS targets.