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Re: A question about define_insn and force-reg

From: Paolo Bonzini <bonzini at gnu dot org>
To: gcc at gcc dot gnu dot org
Date: Tue, 25 Oct 2005 10:52:46 +0200
Subject: Re: A question about define_insn and force-reg
References: <d6afecde0510250100ifbe906h@mail.gmail.com>

  (define_insn "loadsf"
  [(set (match_operand:SF 0 "register_operand" "=r")
        (mem:SF (match_operand:SI 1 "immediate_operand" "m")))]

This makes no sense, because the constraint means that the mem's operand is an immediate before reload (and you want it to be a register), and a mem after reload. What you want is something like

(mem:SF (match_operand:SI 1 "general_operand" "r")))]

which means "the address can be a general operand, but after reload we only accept registers here", or

(mem:SF (match_operand:SI 1 "register_operand" "r")))]

Why can't I create a new register? So how should I do to implement it?

You can create new registers only at special places. GCC tries passing a SYMBOL_REF to gen_mov<mode>. To convert it, use a define_expand.

Paolo

References:
- A question about define_insn and force-reg
  - From: Eric Fisher

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