A pile of long over-due refactorings here. There are some very, *very*

minor behavior changes with this, but nothing I have seen evidence of in
the wild or expect to be meaningful. The real goal is unifying our logic
and simplifying the interfaces. A summary of the changes follows:

- Make 'callIsSmall' actually accept a callsite so it can handle
  intrinsics, and simplify callers appropriately.
- Nuke a completely bogus declaration of 'callIsSmall' that was still
  lurking in InlineCost.h... No idea how this got missed.
- Teach the 'isInstructionFree' about the various more intelligent
  'free' heuristics that got added to the inline cost analysis during
  review and testing. This mostly surrounds int->ptr and ptr->int casts.
- Switch most of the interesting parts of the inline cost analysis that
  were essentially computing 'is this instruction free?' to use the code
  metrics routine instead. This way we won't keep duplicating logic.

All of this is motivated by the desire to allow other passes to compute
a roughly equivalent 'cost' metric for a particular basic block as the
inline cost analysis. Sadly, re-using the same analysis for both is
really messy because only the actual inline cost analysis is ever going
to go to the contortions required for simplification, SROA analysis,
etc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156140 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/CodeMetrics.h

@@ -16,6 +16,7 @@
 #define LLVM_ANALYSIS_CODEMETRICS_H
 
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/Support/CallSite.h"
 
 namespace llvm {
   class BasicBlock;
@@ -29,10 +30,11 @@ namespace llvm {
 
   /// \brief Check whether a call will lower to something small.
   ///
-  /// This tests checks whether calls to this function will lower to something
+  /// This tests checks whether this callsite will lower to something
   /// significantly cheaper than a traditional call, often a single
-  /// instruction.
-  bool callIsSmall(const Function *F);
+  /// instruction. Note that if isInstructionFree(CS.getInstruction()) would
+  /// return true, so will this function.
+  bool callIsSmall(ImmutableCallSite CS);
 
   /// \brief Utility to calculate the size and a few similar metrics for a set
   /// of basic blocks.