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177 lines
6.9 KiB
C++
177 lines
6.9 KiB
C++
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//===- CodeMetrics.cpp - Code cost measurements ---------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements code cost measurement utilities.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/CodeMetrics.h"
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#include "llvm/Function.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Target/TargetData.h"
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using namespace llvm;
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/// callIsSmall - If a call is likely to lower to a single target instruction,
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/// or is otherwise deemed small return true.
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/// TODO: Perhaps calls like memcpy, strcpy, etc?
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bool llvm::callIsSmall(const Function *F) {
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if (!F) return false;
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if (F->hasLocalLinkage()) return false;
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if (!F->hasName()) return false;
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StringRef Name = F->getName();
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// These will all likely lower to a single selection DAG node.
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if (Name == "copysign" || Name == "copysignf" || Name == "copysignl" ||
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Name == "fabs" || Name == "fabsf" || Name == "fabsl" ||
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Name == "sin" || Name == "sinf" || Name == "sinl" ||
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Name == "cos" || Name == "cosf" || Name == "cosl" ||
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Name == "sqrt" || Name == "sqrtf" || Name == "sqrtl" )
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return true;
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// These are all likely to be optimized into something smaller.
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if (Name == "pow" || Name == "powf" || Name == "powl" ||
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Name == "exp2" || Name == "exp2l" || Name == "exp2f" ||
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Name == "floor" || Name == "floorf" || Name == "ceil" ||
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Name == "round" || Name == "ffs" || Name == "ffsl" ||
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Name == "abs" || Name == "labs" || Name == "llabs")
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return true;
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return false;
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}
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/// analyzeBasicBlock - Fill in the current structure with information gleaned
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/// from the specified block.
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void CodeMetrics::analyzeBasicBlock(const BasicBlock *BB,
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const TargetData *TD) {
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++NumBlocks;
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unsigned NumInstsBeforeThisBB = NumInsts;
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for (BasicBlock::const_iterator II = BB->begin(), E = BB->end();
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II != E; ++II) {
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if (isa<PHINode>(II)) continue; // PHI nodes don't count.
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// Special handling for calls.
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if (isa<CallInst>(II) || isa<InvokeInst>(II)) {
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if (const IntrinsicInst *IntrinsicI = dyn_cast<IntrinsicInst>(II)) {
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switch (IntrinsicI->getIntrinsicID()) {
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default: break;
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case Intrinsic::dbg_declare:
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case Intrinsic::dbg_value:
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case Intrinsic::invariant_start:
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case Intrinsic::invariant_end:
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case Intrinsic::lifetime_start:
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case Intrinsic::lifetime_end:
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case Intrinsic::objectsize:
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case Intrinsic::ptr_annotation:
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case Intrinsic::var_annotation:
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// These intrinsics don't count as size.
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continue;
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}
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}
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ImmutableCallSite CS(cast<Instruction>(II));
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if (const Function *F = CS.getCalledFunction()) {
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// If a function is both internal and has a single use, then it is
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// extremely likely to get inlined in the future (it was probably
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// exposed by an interleaved devirtualization pass).
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if (!CS.isNoInline() && F->hasInternalLinkage() && F->hasOneUse())
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++NumInlineCandidates;
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// If this call is to function itself, then the function is recursive.
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// Inlining it into other functions is a bad idea, because this is
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// basically just a form of loop peeling, and our metrics aren't useful
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// for that case.
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if (F == BB->getParent())
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isRecursive = true;
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}
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if (!isa<IntrinsicInst>(II) && !callIsSmall(CS.getCalledFunction())) {
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// Each argument to a call takes on average one instruction to set up.
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NumInsts += CS.arg_size();
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// We don't want inline asm to count as a call - that would prevent loop
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// unrolling. The argument setup cost is still real, though.
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if (!isa<InlineAsm>(CS.getCalledValue()))
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++NumCalls;
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}
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}
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if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
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if (!AI->isStaticAlloca())
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this->usesDynamicAlloca = true;
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}
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if (isa<ExtractElementInst>(II) || II->getType()->isVectorTy())
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++NumVectorInsts;
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if (const CastInst *CI = dyn_cast<CastInst>(II)) {
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// Noop casts, including ptr <-> int, don't count.
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if (CI->isLosslessCast() || isa<IntToPtrInst>(CI) ||
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isa<PtrToIntInst>(CI))
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continue;
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// trunc to a native type is free (assuming the target has compare and
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// shift-right of the same width).
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if (isa<TruncInst>(CI) && TD &&
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TD->isLegalInteger(TD->getTypeSizeInBits(CI->getType())))
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continue;
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// Result of a cmp instruction is often extended (to be used by other
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// cmp instructions, logical or return instructions). These are usually
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// nop on most sane targets.
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if (isa<CmpInst>(CI->getOperand(0)))
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continue;
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} else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(II)){
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// If a GEP has all constant indices, it will probably be folded with
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// a load/store.
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if (GEPI->hasAllConstantIndices())
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continue;
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}
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++NumInsts;
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}
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if (isa<ReturnInst>(BB->getTerminator()))
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++NumRets;
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// We never want to inline functions that contain an indirectbr. This is
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// incorrect because all the blockaddress's (in static global initializers
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// for example) would be referring to the original function, and this indirect
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// jump would jump from the inlined copy of the function into the original
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// function which is extremely undefined behavior.
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// FIXME: This logic isn't really right; we can safely inline functions
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// with indirectbr's as long as no other function or global references the
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// blockaddress of a block within the current function. And as a QOI issue,
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// if someone is using a blockaddress without an indirectbr, and that
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// reference somehow ends up in another function or global, we probably
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// don't want to inline this function.
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if (isa<IndirectBrInst>(BB->getTerminator()))
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containsIndirectBr = true;
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// Remember NumInsts for this BB.
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NumBBInsts[BB] = NumInsts - NumInstsBeforeThisBB;
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}
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void CodeMetrics::analyzeFunction(Function *F, const TargetData *TD) {
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// If this function contains a call that "returns twice" (e.g., setjmp or
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// _setjmp) and it isn't marked with "returns twice" itself, never inline it.
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// This is a hack because we depend on the user marking their local variables
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// as volatile if they are live across a setjmp call, and they probably
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// won't do this in callers.
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exposesReturnsTwice = F->callsFunctionThatReturnsTwice() &&
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!F->hasFnAttr(Attribute::ReturnsTwice);
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// Look at the size of the callee.
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for (Function::const_iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
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analyzeBasicBlock(&*BB, TD);
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}
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