CodeMetrics.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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/CallSite.h"
17#include "llvm/IR/DataLayout.h"
18#include "llvm/IR/Function.h"
19#include "llvm/IR/IntrinsicInst.h"
20
21using namespace llvm;
22
23/// analyzeBasicBlock - Fill in the current structure with information gleaned
24/// from the specified block.
25void 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->cannotDuplicate())
69        notDuplicatable = true;
70
71    if (const InvokeInst *InvI = dyn_cast<InvokeInst>(II))
72      if (InvI->cannotDuplicate())
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