Introduce print-memderefs to test isDereferenceablePointer

Since testing the function indirectly is tricky, introduce a direct
print-memderefs pass, in the same spirit as print-memdeps, which prints
dereferenceability information matched by FileCheck.

Differential Revision: http://reviews.llvm.org/D7075

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228369 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/LinkAllPasses.h

@@ -168,6 +168,7 @@ namespace {
       (void) llvm::createSeparateConstOffsetFromGEPPass();
       (void) llvm::createRewriteSymbolsPass();
       (void) llvm::createStraightLineStrengthReducePass();
+      (void) llvm::createMemDerefPrinter();
 
       (void)new llvm::IntervalPartition();
       (void)new llvm::ScalarEvolution();