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Two simple loop optimizations.
1. Strength reduction of mul[tiplication] by loop induction
variable.
2. Hoisting of (address) base into phi where loop induction
variable is used only as a base (address) offset.
Limited to loops with a single body block, which happily
is always innermost loops. This restriction would not be
very hard to lift - it would require detecting the set of
loop blocks (and ensuring reducibility?)
Limited to loop induction variables with 0 initial value
and increment of 1 (for mul strength reduction). This
limitation is trivial to lift; however all of the
cproc/hare[c]/coremark opportunity is with 0/1 loops for
mul reduction, and 0 initial value for base-offset opt.
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