On Fri, 20 Jul 2001, Richard Earnshaw wrote:

: > The mask is needed when gcc is *compiling* code, so how would this be done
: > at run-time?  (Generation of code that does it on every return insn?  Eek,
: > that sounds like a significant overhead added to function calls....)  Note
: > I'm reading from your definition of "run-time" here that you are implying
: > a program's run-time, not gcc's.

: No, the only time it's needed is when we need to examine the return
: address in "C" code.  At run time the architecture just gets extracting
: the return bits right.  C code unpicking the stack however, has to throw
: away the bits that don't count.  In practise this will only occur when
: unwinding an exception.

OK, that makes sense.  (Trampolines also come to mind, but I'm unsure as to
whether arm uses them extensively.)

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