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.

llvm-svn: 156140

1 files changed, 23 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/CodeMetrics.cpp b/llvm/lib/Analysis/CodeMetrics.cpp
index 316e7bc..acda34b 100644
--- a/llvm/lib/Analysis/CodeMetrics.cpp
+++ b/llvm/lib/Analysis/CodeMetrics.cpp
@@ -22,7 +22,11 @@ using namespace llvm;
 /// callIsSmall - If a call is likely to lower to a single target instruction,
 /// or is otherwise deemed small return true.
 /// TODO: Perhaps calls like memcpy, strcpy, etc?
-bool llvm::callIsSmall(const Function *F) {
+bool llvm::callIsSmall(ImmutableCallSite CS) {
+  if (isa<IntrinsicInst>(CS.getInstruction()))
+    return true;
+
+  const Function *F = CS.getCalledFunction();
   if (!F) return false;
 
   if (F->hasLocalLinkage()) return false;
@@ -79,8 +83,24 @@ bool llvm::isInstructionFree(const Instruction *I, const TargetData *TD) {
 
   if (const CastInst *CI = dyn_cast<CastInst>(I)) {
     // Noop casts, including ptr <-> int,  don't count.
-    if (CI->isLosslessCast() || isa<IntToPtrInst>(CI) || isa<PtrToIntInst>(CI))
+    if (CI->isLosslessCast())
+      return true;
+
+    Value *Op = CI->getOperand(0);
+    // An inttoptr cast is free so long as the input is a legal integer type
+    // which doesn't contain values outside the range of a pointer.
+    if (isa<IntToPtrInst>(CI) && TD &&
+        TD->isLegalInteger(Op->getType()->getScalarSizeInBits()) &&
+        Op->getType()->getScalarSizeInBits() <= TD->getPointerSizeInBits())
       return true;
+
+    // A ptrtoint cast is free so long as the result is large enough to store
+    // the pointer, and a legal integer type.
+    if (isa<PtrToIntInst>(CI) && TD &&
+        TD->isLegalInteger(Op->getType()->getScalarSizeInBits()) &&
+        Op->getType()->getScalarSizeInBits() >= TD->getPointerSizeInBits())
+      return true;
+
     // trunc to a native type is free (assuming the target has compare and
     // shift-right of the same width).
     if (TD && isa<TruncInst>(CI) &&
@@ -126,7 +146,7 @@ void CodeMetrics::analyzeBasicBlock(const BasicBlock *BB,
           isRecursive = true;
       }
 
-      if (!isa<IntrinsicInst>(II) && !callIsSmall(CS.getCalledFunction())) {
+      if (!callIsSmall(CS)) {
         // Each argument to a call takes on average one instruction to set up.
         NumInsts += CS.arg_size();