On Sun, Sep 2, 2012 at 1:02 PM, Peter Bigot <big...@acm.org> wrote:
> 1) The solution mentioned before and made explicit below, which is not
> optimal but does appear to meet your stated requirements for
> atomicity;
Right, I have been investigating that solution, and it's not 100%
reliable. Depending on what the branch structure looks like, the
compiler can sometimes insert a jump which destroys the peephole
optimization. For example:
if (blah)
flags |= some_bit;
else
flags &= ~some_bit;
This sometimes compiles to:
TST.B blah
MOV.B &flags, R14
JZ else
BIS.B #0x0008, R14
JMP skip
else:
AND.B #0x00f7, R14
skip:
MOV.B R14, &flags
I can't just "set it and forget it" with option 1; I have to verify
that the assembly matches my intent, and re-verify it each time I
change something. Option 3 would be more work than option 2, but would
solve this problem once and for all for everyone.
-William
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