3 Aug
2007
3 Aug
'07
9:20 a.m.
On 3 Aug 2007 at 8:02, Brad Parker wrote:
I'll also note that this is a 32 bit machine. My
comments only really
apply to 32 bit machines with a reasonable pipeline and some amount of
branch prediction.
I recall that if one had a particularly large loop or piece of code
to code for the CDC 6600, one approach was to code it in FORTRAN and
compile it with full optimization with generated assembler source.
While this usually didn't give the fastest solution, it usually gave
you a jump start on tweaking the code. Not infrequently, the
optimizer would employ a coding trick that you hadn't thought of.
One of the optimization options that could be specified was the
ominous U flag for "unsafe optimization". Not unsafe in the sense of
producing bad code, but rather in employing optimizations that could
create a protection fault by, say, pre-fetching operands that might,
on the final iteration of a loop, lie outside the program field
length.
Cheers,
Chuck