Initial implementation of the strength reduction for GEP instructions in

loops.  This optimization is not turned on by default yet, but may be run
with the opt tool's -loop-reduce flag.  There are many FIXMEs listed in the
code that will make it far more applicable to a wide range of code, but you
have to start somewhere :)

This limited version currently triggers on the following tests in the
MultiSource directory:
pcompress2: 7 times
cfrac: 5 times
anagram: 2 times
ks: 6 times
yacr2: 2 times


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17134 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Scalar.h

@@ -141,6 +141,12 @@ FunctionPass *createInstructionCombiningPass();
 //
 FunctionPass *createLICMPass();
 
+//===----------------------------------------------------------------------===//
+//
+// LoopStrengthReduce - This pass is strength reduces GEP instructions that use
+// a loop's canonical induction variable as one of their indices.
+//
+FunctionPass *createLoopStrengthReducePass();
 
 //===----------------------------------------------------------------------===//
 //
@@ -155,7 +161,6 @@ FunctionPass *createLoopUnswitchPass();
 //
 FunctionPass *createLoopUnrollPass();
 
-
 //===----------------------------------------------------------------------===//
 //
 // This pass is used to promote memory references to be register references.  A