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[avr-gcc-list] Assembly constraints in words

From: Svein E. Seldal
Subject: [avr-gcc-list] Assembly constraints in words
Date: Tue, 20 Aug 2002 23:47:38 +0200
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.0.0) Gecko/20020530


I want to create an word LPM that is based on the one found in avr-libc, only that this new one reads out a complete word, not just a single byte. How do I constuct the asm constraint? I want to do the following:

    __asm__ (
        "lpm %0, Z+" "\n"
        "lpm %0+1, Z" "\n"
        : "=e" (__result16)
        : "z" (__addr16)
        : "z"

where i want "%0" to be one of the word registers (but not Z, of course) and i want "%0+1" to be this word register +1. I can easily pin it down to use a specific register pair, but I would prefer that gcc still can select what register to use. Can anyone tell me how, please?

PS! Also note that the asm clobbers the z register. Is there a better way to specify that z is input *and* is clobbered?


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