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CALL_USED_REGISTERS help
- From: "Paulo J. Matos" <pocmatos at gmail dot com>
- To: GCC-help <gcc-help at gcc dot gnu dot org>
- Date: Fri, 18 Dec 2009 10:13:26 +0000
- Subject: CALL_USED_REGISTERS help
Hi,
I am reading the documentation of CALL_USED_REGISTERS and can't help
but thing there is a typo (even though it is more probable that I am
not understanding the documentation).
It says:
"Like FIXED_REGISTERS but has 1 for each register that is clobbered
(in general) by function calls as well as for fixed registers. ... If
a register has 0 in CALL_USED_REGISTERS, the compiler automatically
saves it on function entry and restores it on function exit, if the
register is used within the function. "
Is it has a 1, then it means that the register is clobbered. And 0
means it is not clobbered. But if it is not clobbered, why does the
compiler need to save it on function entry and restore it on function
exit?
I am not getting it...
Thanks,
--
Paulo Jorge Matos - pocmatos at gmail.com
http://www.pmatos.net