move patterns, emit_move_insn

[Ian Lance Taylor]

Florent DEFAY <spira.inhabitant@gmail.com> writes:

> And move in HImode is defined by these patterns in the md :

The movMM patterns are special.  You must have a single define_insn
which matches all moves in a given mode, with alternatives which support
all the different possibilities.  Unlike other instructions, you can not
use different insns to match different cases.  The single insn doesn't
literally have to be movhi--that can be a define_expand.  But there must
be one insn.  The reload pass depends on this.

Ian