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> Date: Tue, 31 Aug 2010 21:24:07 -0500<BR>> From: rodney_bates@<BR>> <BR>> If the writers of an ABI actually *required* that small structs/records be<BR>> passed in registers<BR>
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Yes, they have. The rules are hard for me to understand. It isn't just based on size.<BR>
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> then they have made a big blunder.<BR>
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No they have not. They know what they are doing.<BR>
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> Thus taking their address must always be possible,<BR>
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If they have to be in memory, then they will be put in memory, at or before<BR>
the address is taken. That doesn't mean the parameters have to be passed in memory.<BR>
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<BR>> 1) Declare that language semantics trump ABI requirements and defy the ABI.<BR>
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Not necessary.<BR>
Granted, we don't have to follow the ABI. The ABI is for interoperability with C.<BR>
I'm plenty willing to say you can't pass records by value between C and Modula-3.<BR>
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<BR><BR>> 2) Pass them in registers at the time of control transfer, but store them<BR>> in memory in the prologue, then access them from memory thereafter.<BR>
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The backend does that as needed for C already.<BR>
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Data can live in multiple places.<BR>
Just that there can be only be one mutable location at a time.<BR>
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<BR>Look at the code generated Tony asked about, add like<BR>
printr("%p\n", &t);<BR>
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you'll see the registers get written to the stack.<BR>
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- Jay<BR> </body>
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