Begin fleshing out an interface in TTI for modelling the costs of

generic function calls and intrinsics. This is somewhat overlapping with
an existing intrinsic cost method, but that one seems targetted at
vector intrinsics. I'll merge them or separate their names and use cases
in a separate commit.

This sinks the test of 'callIsSmall' down into TTI where targets can
control it. The whole thing feels very hack-ish to me though. I've left
a FIXME comment about the fundamental design problem this presents. It
isn't yet clear to me what the users of this function *really* care
about. I'll have to do more analysis to figure that out. Putting this
here at least provides it access to proper analysis pass tools and other
such. It also allows us to more cleanly implement the baseline cost
interfaces in TTI.

With this commit, it is now theoretically possible to simplify much of
the inline cost analysis's handling of calls by calling through to this
interface. That conversion will have to happen in subsequent commits as
it requires more extensive restructuring of the inline cost analysis.

The CodeMetrics class is now really only in the business of running over
a block of code and aggregating the metrics on that block of code, with
the actual cost evaluation done entirely in terms of TTI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173148 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 3 deletions

diff --git a/lib/Transforms/Scalar/TailRecursionElimination.cpp b/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 6572e09..2002e68 100644
--- a/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -58,6 +58,7 @@
 #include "llvm/Analysis/InlineCost.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/Loads.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
@@ -79,11 +80,15 @@ STATISTIC(NumAccumAdded, "Number of accumulators introduced");
 
 namespace {
   struct TailCallElim : public FunctionPass {
+    const TargetTransformInfo *TTI;
+
     static char ID; // Pass identification, replacement for typeid
     TailCallElim() : FunctionPass(ID) {
       initializeTailCallElimPass(*PassRegistry::getPassRegistry());
     }
 
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+
     virtual bool runOnFunction(Function &F);
 
   private:
@@ -109,14 +114,21 @@ namespace {
 }
 
 char TailCallElim::ID = 0;
-INITIALIZE_PASS(TailCallElim, "tailcallelim",
-                "Tail Call Elimination", false, false)
+INITIALIZE_PASS_BEGIN(TailCallElim, "tailcallelim",
+                      "Tail Call Elimination", false, false)
+INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
+INITIALIZE_PASS_END(TailCallElim, "tailcallelim",
+                    "Tail Call Elimination", false, false)
 
 // Public interface to the TailCallElimination pass
 FunctionPass *llvm::createTailCallEliminationPass() {
   return new TailCallElim();
 }
 
+void TailCallElim::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequired<TargetTransformInfo>();
+}
+
 /// AllocaMightEscapeToCalls - Return true if this alloca may be accessed by
 /// callees of this function.  We only do very simple analysis right now, this
 /// could be expanded in the future to use mod/ref information for particular
@@ -151,6 +163,7 @@ bool TailCallElim::runOnFunction(Function &F) {
   // right, so don't even try to convert it...
   if (F.getFunctionType()->isVarArg()) return false;
 
+  TTI = &getAnalysis<TargetTransformInfo>();
   BasicBlock *OldEntry = 0;
   bool TailCallsAreMarkedTail = false;
   SmallVector<PHINode*, 8> ArgumentPHIs;
@@ -391,7 +404,8 @@ TailCallElim::FindTRECandidate(Instruction *TI,
   if (BB == &F->getEntryBlock() &&
       FirstNonDbg(BB->front()) == CI &&
       FirstNonDbg(llvm::next(BB->begin())) == TI &&
-      callIsSmall(CI)) {
+      CI->getCalledFunction() &&
+      !TTI->isLoweredToCall(CI->getCalledFunction())) {
     // A single-block function with just a call and a return. Check that
     // the arguments match.
     CallSite::arg_iterator I = CallSite(CI).arg_begin(),