From: Doug Evans <dje@transmeta.com>
To: Dave Brolley <brolley@redhat.com>
Cc: cgen@sourceware.cygnus.com
Subject: CGEN: RELAXABLE and RELAX
Date: Tue, 22 Aug 2000 13:33:00 -0000 [thread overview]
Message-ID: <14754.58225.474553.670993@casey.transmeta.com> (raw)
In-Reply-To: <399D5EC7.C59F3DEF@redhat.com>
Dave Brolley writes:
> The architecture I'm working with has two load immediate insns
> that look syntactically identical except for the range of the
> immediate value allowed:
>
> ld Rn,imm8 ; 8 bit immediate
> ld Rn,imm16 ; 16 bit immediate
>
> The 8 bit load assembles to a 16 bit insn and the 16 bit load
> assembles to a 32 bit insn. From the reading the CGEN manual, it
> looks to me like this is what RELAXABLE and RELAX are supposed to
> handle. i.e. specifying RELAXABLE on the 8 bit load will cause it
> to be tried first during assembly and specifying RELAX on the 16
> bit load will cause it to be tried next. I tried this, but when I
> code 'ld r1,0x100', I get an error saying bad instruction. 'ld
> r1,0xff' assembles correctly. It looks like the 16 bit load was
> never considered. Am I missing something?
Hi, you're latest message reminded me I never answered this one.
IIRC, RELAXABLE,RELAX in and of themselves aren't sufficient.
Also, you're definitions of RELAXABLE,RELAX aren't quite correct.
[probably stemming from the documentation]
RELAX: don't try during assembly
From m32r_cgen_assemble_insn:
/* If the RELAX attribute is set, this is an insn that shouldn't be
chosen immediately. Instead, it is used during assembler/linker
relaxation if possible. */
if (CGEN_INSN_ATTR_VALUE (insn, CGEN_INSN_RELAX) != 0)
continue;
Also, RELAX/RELAXABLE aren't generally used for this case.
What you do here is specify 8 bit loads a head of 16 bit loads.
The assembler will pick the first applicable one.
[kinda hokey, but sufficient for now]
prev parent reply other threads:[~2000-08-22 13:33 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-08-18 9:04 Dave Brolley
2000-08-22 13:33 ` Doug Evans [this message]
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