Simple Inner Loop Optimzationloopopt

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.

1 files changed, 2 insertions, 0 deletions

diff --git a/main.c b/main.c
index 7a97f8a..ae73ba1 100644
--- a/main.c
+++ b/main.c
@@ -81,6 +81,8 @@ func(Fn *fn)
 	gcm(fn);
 	filluse(fn);
 	ssacheck(fn);
+	loopopt(fn);
+	filluse(fn);
 	T.abi1(fn);
 	simpl(fn);
 	fillcfg(fn);