Import LLVM, at r72732.

1 files changed, 315 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/InlineCost.cpp b/lib/Transforms/Utils/InlineCost.cpp
new file mode 100644
index 0000000..87aff01
--- /dev/null
+++ b/lib/Transforms/Utils/InlineCost.cpp
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+//===- InlineCost.cpp - Cost analysis for inliner -------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements inline cost analysis.
+//
+//===----------------------------------------------------------------------===//
+
+
+#include "llvm/Transforms/Utils/InlineCost.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/CallingConv.h"
+#include "llvm/IntrinsicInst.h"
+
+using namespace llvm;
+
+// CountCodeReductionForConstant - Figure out an approximation for how many
+// instructions will be constant folded if the specified value is constant.
+//
+unsigned InlineCostAnalyzer::FunctionInfo::
+         CountCodeReductionForConstant(Value *V) {
+  unsigned Reduction = 0;
+  for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
+    if (isa<BranchInst>(*UI))
+      Reduction += 40;          // Eliminating a conditional branch is a big win
+    else if (SwitchInst *SI = dyn_cast<SwitchInst>(*UI))
+      // Eliminating a switch is a big win, proportional to the number of edges
+      // deleted.
+      Reduction += (SI->getNumSuccessors()-1) * 40;
+    else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
+      // Turning an indirect call into a direct call is a BIG win
+      Reduction += CI->getCalledValue() == V ? 500 : 0;
+    } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
+      // Turning an indirect call into a direct call is a BIG win
+      Reduction += II->getCalledValue() == V ? 500 : 0;
+    } else {
+      // Figure out if this instruction will be removed due to simple constant
+      // propagation.
+      Instruction &Inst = cast<Instruction>(**UI);
+      bool AllOperandsConstant = true;
+      for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i)
+        if (!isa<Constant>(Inst.getOperand(i)) && Inst.getOperand(i) != V) {
+          AllOperandsConstant = false;
+          break;
+        }
+
+      if (AllOperandsConstant) {
+        // We will get to remove this instruction...
+        Reduction += 7;
+
+        // And any other instructions that use it which become constants
+        // themselves.
+        Reduction += CountCodeReductionForConstant(&Inst);
+      }
+    }
+
+  return Reduction;
+}
+
+// CountCodeReductionForAlloca - Figure out an approximation of how much smaller
+// the function will be if it is inlined into a context where an argument
+// becomes an alloca.
+//
+unsigned InlineCostAnalyzer::FunctionInfo::
+         CountCodeReductionForAlloca(Value *V) {
+  if (!isa<PointerType>(V->getType())) return 0;  // Not a pointer
+  unsigned Reduction = 0;
+  for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
+    Instruction *I = cast<Instruction>(*UI);
+    if (isa<LoadInst>(I) || isa<StoreInst>(I))
+      Reduction += 10;
+    else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
+      // If the GEP has variable indices, we won't be able to do much with it.
+      if (!GEP->hasAllConstantIndices())
+        Reduction += CountCodeReductionForAlloca(GEP)+15;
+    } else {
+      // If there is some other strange instruction, we're not going to be able
+      // to do much if we inline this.
+      return 0;
+    }
+  }
+
+  return Reduction;
+}
+
+/// analyzeFunction - Fill in the current structure with information gleaned
+/// from the specified function.
+void InlineCostAnalyzer::FunctionInfo::analyzeFunction(Function *F) {
+  unsigned NumInsts = 0, NumBlocks = 0, NumVectorInsts = 0;
+
+  // Look at the size of the callee.  Each basic block counts as 20 units, and
+  // each instruction counts as 5.
+  for (Function::const_iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+    for (BasicBlock::const_iterator II = BB->begin(), E = BB->end();
+         II != E; ++II) {
+      if (isa<PHINode>(II)) continue;           // PHI nodes don't count.
+
+      // Special handling for calls.
+      if (isa<CallInst>(II) || isa<InvokeInst>(II)) {
+        if (isa<DbgInfoIntrinsic>(II))
+          continue;  // Debug intrinsics don't count as size.
+        
+        CallSite CS = CallSite::get(const_cast<Instruction*>(&*II));
+        
+        // If this function contains a call to setjmp or _setjmp, never inline
+        // it.  This is a hack because we depend on the user marking their local
+        // variables as volatile if they are live across a setjmp call, and they
+        // probably won't do this in callers.
+        if (Function *F = CS.getCalledFunction())
+          if (F->isDeclaration() && 
+              (F->isName("setjmp") || F->isName("_setjmp"))) {
+            NeverInline = true;
+            return;
+          }
+
+        // Calls often compile into many machine instructions.  Bump up their
+        // cost to reflect this.
+        if (!isa<IntrinsicInst>(II))
+          NumInsts += 5;
+      }
+      
+      if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
+        if (!AI->isStaticAlloca())
+          this->usesDynamicAlloca = true;
+      }
+
+      if (isa<ExtractElementInst>(II) || isa<VectorType>(II->getType()))
+        ++NumVectorInsts; 
+      
+      // Noop casts, including ptr <-> int,  don't count.
+      if (const CastInst *CI = dyn_cast<CastInst>(II)) {
+        if (CI->isLosslessCast() || isa<IntToPtrInst>(CI) || 
+            isa<PtrToIntInst>(CI))
+          continue;
+      } else if (const GetElementPtrInst *GEPI =
+                 dyn_cast<GetElementPtrInst>(II)) {
+        // If a GEP has all constant indices, it will probably be folded with
+        // a load/store.
+        if (GEPI->hasAllConstantIndices())
+          continue;
+      }
+      
+      ++NumInsts;
+    }
+
+    ++NumBlocks;
+  }
+
+  this->NumBlocks      = NumBlocks;
+  this->NumInsts       = NumInsts;
+  this->NumVectorInsts = NumVectorInsts;
+
+  // Check out all of the arguments to the function, figuring out how much
+  // code can be eliminated if one of the arguments is a constant.
+  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
+    ArgumentWeights.push_back(ArgInfo(CountCodeReductionForConstant(I),
+                                      CountCodeReductionForAlloca(I)));
+}
+
+
+
+// getInlineCost - The heuristic used to determine if we should inline the
+// function call or not.
+//
+InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS,
+                               SmallPtrSet<const Function *, 16> &NeverInline) {
+  Instruction *TheCall = CS.getInstruction();
+  Function *Callee = CS.getCalledFunction();
+  Function *Caller = TheCall->getParent()->getParent();
+
+      // Don't inline functions which can be redefined at link-time to mean
+      // something else.
+   if (Callee->mayBeOverridden() ||
+       // Don't inline functions marked noinline.
+       Callee->hasFnAttr(Attribute::NoInline) || NeverInline.count(Callee))
+    return llvm::InlineCost::getNever();
+
+  // InlineCost - This value measures how good of an inline candidate this call
+  // site is to inline.  A lower inline cost make is more likely for the call to
+  // be inlined.  This value may go negative.
+  //
+  int InlineCost = 0;
+  
+  // If there is only one call of the function, and it has internal linkage,
+  // make it almost guaranteed to be inlined.
+  //
+  if ((Callee->hasLocalLinkage() || Callee->hasAvailableExternallyLinkage()) && 
+      Callee->hasOneUse())
+    InlineCost -= 15000;
+  
+  // If this function uses the coldcc calling convention, prefer not to inline
+  // it.
+  if (Callee->getCallingConv() == CallingConv::Cold)
+    InlineCost += 2000;
+  
+  // If the instruction after the call, or if the normal destination of the
+  // invoke is an unreachable instruction, the function is noreturn.  As such,
+  // there is little point in inlining this.
+  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
+    if (isa<UnreachableInst>(II->getNormalDest()->begin()))
+      InlineCost += 10000;
+  } else if (isa<UnreachableInst>(++BasicBlock::iterator(TheCall)))
+    InlineCost += 10000;
+  
+  // Get information about the callee...
+  FunctionInfo &CalleeFI = CachedFunctionInfo[Callee];
+  
+  // If we haven't calculated this information yet, do so now.
+  if (CalleeFI.NumBlocks == 0)
+    CalleeFI.analyzeFunction(Callee);
+
+  // If we should never inline this, return a huge cost.
+  if (CalleeFI.NeverInline)
+    return InlineCost::getNever();
+
+  // FIXME: It would be nice to kill off CalleeFI.NeverInline. Then we
+  // could move this up and avoid computing the FunctionInfo for
+  // things we are going to just return always inline for. This
+  // requires handling setjmp somewhere else, however.
+  if (!Callee->isDeclaration() && Callee->hasFnAttr(Attribute::AlwaysInline))
+    return InlineCost::getAlways();
+    
+  if (CalleeFI.usesDynamicAlloca) {
+    // Get infomation about the caller...
+    FunctionInfo &CallerFI = CachedFunctionInfo[Caller];
+
+    // If we haven't calculated this information yet, do so now.
+    if (CallerFI.NumBlocks == 0)
+      CallerFI.analyzeFunction(Caller);
+
+    // Don't inline a callee with dynamic alloca into a caller without them.
+    // Functions containing dynamic alloca's are inefficient in various ways;
+    // don't create more inefficiency.
+    if (!CallerFI.usesDynamicAlloca)
+      return InlineCost::getNever();
+  }
+
+  // Add to the inline quality for properties that make the call valuable to
+  // inline.  This includes factors that indicate that the result of inlining
+  // the function will be optimizable.  Currently this just looks at arguments
+  // passed into the function.
+  //
+  unsigned ArgNo = 0;
+  for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+       I != E; ++I, ++ArgNo) {
+    // Each argument passed in has a cost at both the caller and the callee
+    // sides.  This favors functions that take many arguments over functions
+    // that take few arguments.
+    InlineCost -= 20;
+    
+    // If this is a function being passed in, it is very likely that we will be
+    // able to turn an indirect function call into a direct function call.
+    if (isa<Function>(I))
+      InlineCost -= 100;
+    
+    // If an alloca is passed in, inlining this function is likely to allow
+    // significant future optimization possibilities (like scalar promotion, and
+    // scalarization), so encourage the inlining of the function.
+    //
+    else if (isa<AllocaInst>(I)) {
+      if (ArgNo < CalleeFI.ArgumentWeights.size())
+        InlineCost -= CalleeFI.ArgumentWeights[ArgNo].AllocaWeight;
+      
+      // If this is a constant being passed into the function, use the argument
+      // weights calculated for the callee to determine how much will be folded
+      // away with this information.
+    } else if (isa<Constant>(I)) {
+      if (ArgNo < CalleeFI.ArgumentWeights.size())
+        InlineCost -= CalleeFI.ArgumentWeights[ArgNo].ConstantWeight;
+    }
+  }
+  
+  // Now that we have considered all of the factors that make the call site more
+  // likely to be inlined, look at factors that make us not want to inline it.
+  
+  // Don't inline into something too big, which would make it bigger.
+  //
+  InlineCost += Caller->size()/15;
+  
+  // Look at the size of the callee. Each instruction counts as 5.
+  InlineCost += CalleeFI.NumInsts*5;
+
+  return llvm::InlineCost::get(InlineCost);
+}
+
+// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a
+// higher threshold to determine if the function call should be inlined.
+float InlineCostAnalyzer::getInlineFudgeFactor(CallSite CS) {
+  Function *Callee = CS.getCalledFunction();
+  
+  // Get information about the callee...
+  FunctionInfo &CalleeFI = CachedFunctionInfo[Callee];
+  
+  // If we haven't calculated this information yet, do so now.
+  if (CalleeFI.NumBlocks == 0)
+    CalleeFI.analyzeFunction(Callee);
+
+  float Factor = 1.0f;
+  // Single BB functions are often written to be inlined.
+  if (CalleeFI.NumBlocks == 1)
+    Factor += 0.5f;
+
+  // Be more aggressive if the function contains a good chunk (if it mades up
+  // at least 10% of the instructions) of vector instructions.
+  if (CalleeFI.NumVectorInsts > CalleeFI.NumInsts/2)
+    Factor += 2.0f;
+  else if (CalleeFI.NumVectorInsts > CalleeFI.NumInsts/10)
+    Factor += 1.5f;
+  return Factor;
+}