Move the InlineCost code from Transforms/Utils to Analysis.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83998 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp
new file mode 100644
index 0000000..e77fbd1
--- /dev/null
+++ b/lib/Analysis/InlineCost.cpp
@@ -0,0 +1,337 @@
+//===- 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/Analysis/InlineCost.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/CallingConv.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/ADT/SmallPtrSet.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::RegionInfo::
+ 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);
+
+ // We can't constant propagate instructions which have effects or
+ // read memory.
+ //
+ // FIXME: It would be nice to capture the fact that a load from a
+ // pointer-to-constant-global is actually a *really* good thing to zap.
+ // Unfortunately, we don't know the pointer that may get propagated here,
+ // so we can't make this decision.
+ if (Inst.mayReadFromMemory() || Inst.mayHaveSideEffects() ||
+ isa<AllocationInst>(Inst))
+ continue;
+
+ 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::RegionInfo::
+ 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;
+}
+
+/// analyzeBasicBlock - Fill in the current structure with information gleaned
+/// from the specified block.
+void InlineCostAnalyzer::RegionInfo::analyzeBasicBlock(const BasicBlock *BB) {
+ ++NumBlocks;
+
+ 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->getName() == "setjmp" || F->getName() == "_setjmp")) {
+ NeverInline = true;
+ return;
+ }
+
+ // Calls often compile into many machine instructions. Bump up their
+ // cost to reflect this.
+ if (!isa<IntrinsicInst>(II))
+ NumInsts += InlineConstants::CallPenalty;
+ }
+
+ // These, too, are calls.
+ if (isa<MallocInst>(II) || isa<FreeInst>(II))
+ NumInsts += InlineConstants::CallPenalty;
+
+ 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;
+ }
+
+ if (isa<ReturnInst>(II))
+ ++NumRets;
+
+ ++NumInsts;
+ }
+}
+
+/// analyzeFunction - Fill in the current structure with information gleaned
+/// from the specified function.
+void InlineCostAnalyzer::RegionInfo::analyzeFunction(Function *F) {
+ // 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)
+ analyzeBasicBlock(&*BB);
+
+ // A function with exactly one return has it removed during the inlining
+ // process (see InlineFunction), so don't count it.
+ // FIXME: This knowledge should really be encoded outside of RegionInfo.
+ if (NumRets==1)
+ --NumInsts;
+
+ // 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. Don't inline functions marked noinline.
+ if (Callee->mayBeOverridden() ||
+ 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->hasOneUse())
+ InlineCost += InlineConstants::LastCallToStaticBonus;
+
+ // If this function uses the coldcc calling convention, prefer not to inline
+ // it.
+ if (Callee->getCallingConv() == CallingConv::Cold)
+ InlineCost += InlineConstants::ColdccPenalty;
+
+ // 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 += InlineConstants::NoreturnPenalty;
+ } else if (isa<UnreachableInst>(++BasicBlock::iterator(TheCall)))
+ InlineCost += InlineConstants::NoreturnPenalty;
+
+ // Get information about the callee...
+ RegionInfo &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 RegionInfo 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...
+ RegionInfo &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.
+ // "size" here is the number of basic blocks, not instructions.
+ //
+ 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...
+ RegionInfo &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;
+}