Hello, I am working on a gcc porting for a new instruction. This instruction needs to move data from memory to two registers. So I use the SET rtx, and the dest of SET is an UNSPEC rtx with two registers. By using such a rtl pattern, gcc performs very differently. It makes mistakes for register replacement and instruction reordering. For example, when gcc optimizes in pass_cse, it performs register substitution of registers in UNSPEC rtx without checking the validity of the resulting insn. So I wonder about the UNSPEC rtx.
What's the usage of UNSPEC rtx? And do you have a better rtl pattern for this new instruction? Thanks, Jacy
