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      1 //===- CodeMetrics.cpp - Code cost measurements ---------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements code cost measurement utilities.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/Analysis/CodeMetrics.h"
     15 #include "llvm/Analysis/TargetTransformInfo.h"
     16 #include "llvm/IR/DataLayout.h"
     17 #include "llvm/IR/Function.h"
     18 #include "llvm/IR/IntrinsicInst.h"
     19 #include "llvm/Support/CallSite.h"
     20 
     21 using namespace llvm;
     22 
     23 /// analyzeBasicBlock - Fill in the current structure with information gleaned
     24 /// from the specified block.
     25 void CodeMetrics::analyzeBasicBlock(const BasicBlock *BB,
     26                                     const TargetTransformInfo &TTI) {
     27   ++NumBlocks;
     28   unsigned NumInstsBeforeThisBB = NumInsts;
     29   for (BasicBlock::const_iterator II = BB->begin(), E = BB->end();
     30        II != E; ++II) {
     31     // Special handling for calls.
     32     if (isa<CallInst>(II) || isa<InvokeInst>(II)) {
     33       ImmutableCallSite CS(cast<Instruction>(II));
     34 
     35       if (const Function *F = CS.getCalledFunction()) {
     36         // If a function is both internal and has a single use, then it is
     37         // extremely likely to get inlined in the future (it was probably
     38         // exposed by an interleaved devirtualization pass).
     39         if (!CS.isNoInline() && F->hasInternalLinkage() && F->hasOneUse())
     40           ++NumInlineCandidates;
     41 
     42         // If this call is to function itself, then the function is recursive.
     43         // Inlining it into other functions is a bad idea, because this is
     44         // basically just a form of loop peeling, and our metrics aren't useful
     45         // for that case.
     46         if (F == BB->getParent())
     47           isRecursive = true;
     48 
     49         if (TTI.isLoweredToCall(F))
     50           ++NumCalls;
     51       } else {
     52         // We don't want inline asm to count as a call - that would prevent loop
     53         // unrolling. The argument setup cost is still real, though.
     54         if (!isa<InlineAsm>(CS.getCalledValue()))
     55           ++NumCalls;
     56       }
     57     }
     58 
     59     if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
     60       if (!AI->isStaticAlloca())
     61         this->usesDynamicAlloca = true;
     62     }
     63 
     64     if (isa<ExtractElementInst>(II) || II->getType()->isVectorTy())
     65       ++NumVectorInsts;
     66 
     67     if (const CallInst *CI = dyn_cast<CallInst>(II))
     68       if (CI->hasFnAttr(Attribute::NoDuplicate))
     69         notDuplicatable = true;
     70 
     71     if (const InvokeInst *InvI = dyn_cast<InvokeInst>(II))
     72       if (InvI->hasFnAttr(Attribute::NoDuplicate))
     73         notDuplicatable = true;
     74 
     75     NumInsts += TTI.getUserCost(&*II);
     76   }
     77 
     78   if (isa<ReturnInst>(BB->getTerminator()))
     79     ++NumRets;
     80 
     81   // We never want to inline functions that contain an indirectbr.  This is
     82   // incorrect because all the blockaddress's (in static global initializers
     83   // for example) would be referring to the original function, and this indirect
     84   // jump would jump from the inlined copy of the function into the original
     85   // function which is extremely undefined behavior.
     86   // FIXME: This logic isn't really right; we can safely inline functions
     87   // with indirectbr's as long as no other function or global references the
     88   // blockaddress of a block within the current function.  And as a QOI issue,
     89   // if someone is using a blockaddress without an indirectbr, and that
     90   // reference somehow ends up in another function or global, we probably
     91   // don't want to inline this function.
     92   notDuplicatable |= isa<IndirectBrInst>(BB->getTerminator());
     93 
     94   // Remember NumInsts for this BB.
     95   NumBBInsts[BB] = NumInsts - NumInstsBeforeThisBB;
     96 }
     97