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, 3 insertions, 0 deletions

diff --git a/all.h b/all.h
index 39a4f7c..a86c85b 100644
--- a/all.h
+++ b/all.h
@@ -595,6 +595,9 @@ void gvn(Fn *);
 int pinned(Ins *);
 void gcm(Fn *);
 
+/* loopopt.c */
+void loopopt(Fn *fn);
+
 /* simpl.c */
 void simpl(Fn *);