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* Separate all of the grunt work of inlining out into the Utils library.

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* Make the function inliner _significantly_ smarter.  :)

llvm-svn: 6396
This commit is contained in:
Chris Lattner 2003-05-29 15:11:31 +00:00
parent d3eae6379d
commit 24947af013
2 changed files with 313 additions and 191 deletions
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340
lib/Transforms/IPO/InlineSimple.cpp
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@ -1,15 +1,6 @@
//===- FunctionInlining.cpp - Code to perform function inlining -----------===//
//
// This file implements inlining of functions.
//
// Specifically, this:
// * Exports functionality to inline any function call
// * Inlines functions that consist of a single basic block
// * Is able to inline ANY function call
// . Has a smart heuristic for when to inline a function
//
// FIXME: This pass should transform alloca instructions in the called function
// into malloc/free pairs! Or perhaps it should refuse to inline them!
// This file implements bottom-up inlining of functions into callees.
//
//===----------------------------------------------------------------------===//
@ -17,194 +8,161 @@
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/iTerminators.h"
#include "llvm/iPHINode.h"
#include "llvm/iOther.h"
#include "llvm/DerivedTypes.h"
#include "llvm/iMemory.h"
#include "Support/Statistic.h"
#include <algorithm>
static Statistic<> NumInlined("inline", "Number of functions inlined");
// InlineFunction - This function forcibly inlines the called function into the
// basic block of the caller. This returns false if it is not possible to
// inline this call. The program is still in a well defined state if this
// occurs though.
//
// Note that this only does one level of inlining. For example, if the
// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
// exists in the instruction stream. Similiarly this will inline a recursive
// function by one level.
//
bool InlineFunction(CallInst *CI) {
assert(isa<CallInst>(CI) && "InlineFunction only works on CallInst nodes");
assert(CI->getParent() && "Instruction not embedded in basic block!");
assert(CI->getParent()->getParent() && "Instruction not in function!");
const Function *CalledFunc = CI->getCalledFunction();
if (CalledFunc == 0 || // Can't inline external function or indirect
CalledFunc->isExternal() || // call, or call to a vararg function!
CalledFunc->getFunctionType()->isVarArg()) return false;
//std::cerr << "Inlining " << CalledFunc->getName() << " into "
// << CurrentMeth->getName() << "\n";
BasicBlock *OrigBB = CI->getParent();
// Call splitBasicBlock - The original basic block now ends at the instruction
// immediately before the call. The original basic block now ends with an
// unconditional branch to NewBB, and NewBB starts with the call instruction.
//
BasicBlock *NewBB = OrigBB->splitBasicBlock(CI);
NewBB->setName("InlinedFunctionReturnNode");
// Remove (unlink) the CallInst from the start of the new basic block.
NewBB->getInstList().remove(CI);
// If we have a return value generated by this call, convert it into a PHI
// node that gets values from each of the old RET instructions in the original
// function.
//
PHINode *PHI = 0;
if (!CI->use_empty()) {
// The PHI node should go at the front of the new basic block to merge all
// possible incoming values.
//
PHI = new PHINode(CalledFunc->getReturnType(), CI->getName(),
NewBB->begin());
// Anything that used the result of the function call should now use the PHI
// node as their operand.
//
CI->replaceAllUsesWith(PHI);
}
// Get a pointer to the last basic block in the function, which will have the
// new function inlined after it.
//
Function::iterator LastBlock = &OrigBB->getParent()->back();
// Calculate the vector of arguments to pass into the function cloner...
std::map<const Value*, Value*> ValueMap;
assert((unsigned)std::distance(CalledFunc->abegin(), CalledFunc->aend()) ==
CI->getNumOperands()-1 && "No varargs calls can be inlined yet!");
unsigned i = 1;
for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend();
I != E; ++I, ++i)
ValueMap[I] = CI->getOperand(i);
// Since we are now done with the CallInst, we can delete it.
delete CI;
// Make a vector to capture the return instructions in the cloned function...
std::vector<ReturnInst*> Returns;
// Populate the value map with all of the globals in the program.
Module &M = *OrigBB->getParent()->getParent();
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
ValueMap[I] = I;
for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
ValueMap[I] = I;
// Do all of the hard part of cloning the callee into the caller...
CloneFunctionInto(OrigBB->getParent(), CalledFunc, ValueMap, Returns, ".i");
// Loop over all of the return instructions, turning them into unconditional
// branches to the merge point now...
for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
ReturnInst *RI = Returns[i];
BasicBlock *BB = RI->getParent();
// Add a branch to the merge point where the PHI node would live...
new BranchInst(NewBB, RI);
if (PHI) { // The PHI node should include this value!
assert(RI->getReturnValue() && "Ret should have value!");
assert(RI->getReturnValue()->getType() == PHI->getType() &&
"Ret value not consistent in function!");
PHI->addIncoming(RI->getReturnValue(), BB);
}
// Delete the return instruction now
BB->getInstList().erase(RI);
}
// Check to see if the PHI node only has one argument. This is a common
// case resulting from there only being a single return instruction in the
// function call. Because this is so common, eliminate the PHI node.
//
if (PHI && PHI->getNumIncomingValues() == 1) {
PHI->replaceAllUsesWith(PHI->getIncomingValue(0));
PHI->getParent()->getInstList().erase(PHI);
}
// Change the branch that used to go to NewBB to branch to the first basic
// block of the inlined function.
//
TerminatorInst *Br = OrigBB->getTerminator();
assert(Br && Br->getOpcode() == Instruction::Br &&
"splitBasicBlock broken!");
Br->setOperand(0, ++LastBlock);
return true;
}
static inline bool ShouldInlineFunction(const CallInst *CI, const Function *F) {
assert(CI->getParent() && CI->getParent()->getParent() &&
"Call not embedded into a function!");
// Don't inline a recursive call.
if (CI->getParent()->getParent() == F) return false;
// Don't inline something too big. This is a really crappy heuristic
if (F->size() > 3) return false;
// Don't inline into something too big. This is a **really** crappy heuristic
if (CI->getParent()->getParent()->size() > 10) return false;
// Go ahead and try just about anything else.
return true;
}
static inline bool DoFunctionInlining(BasicBlock *BB) {
for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
if (CallInst *CI = dyn_cast<CallInst>(I)) {
// Check to see if we should inline this function
Function *F = CI->getCalledFunction();
if (F && ShouldInlineFunction(CI, F)) {
return InlineFunction(CI);
}
}
}
return false;
}
// doFunctionInlining - Use a heuristic based approach to inline functions that
// seem to look good.
//
static bool doFunctionInlining(Function &F) {
bool Changed = false;
// Loop through now and inline instructions a basic block at a time...
for (Function::iterator I = F.begin(); I != F.end(); )
if (DoFunctionInlining(I)) {
++NumInlined;
Changed = true;
} else {
++I;
}
return Changed;
}
#include <set>
namespace {
struct FunctionInlining : public FunctionPass {
virtual bool runOnFunction(Function &F) {
return doFunctionInlining(F);
Statistic<> NumInlined("inline", "Number of functions inlined");
struct FunctionInlining : public Pass {
virtual bool run(Module &M) {
bool Changed = false;
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
Changed |= doInlining(I);
ProcessedFunctions.clear();
return Changed;
}
private:
std::set<Function*> ProcessedFunctions; // Prevent infinite recursion
bool doInlining(Function *F);
};
RegisterOpt<FunctionInlining> X("inline", "Function Integration/Inlining");
}
Pass *createFunctionInliningPass() { return new FunctionInlining(); }
// ShouldInlineFunction - The heuristic used to determine if we should inline
// the function call or not.
//
static inline bool ShouldInlineFunction(const CallInst *CI) {
assert(CI->getParent() && CI->getParent()->getParent() &&
"Call not embedded into a function!");
const Function *Callee = CI->getCalledFunction();
if (Callee == 0 || Callee->isExternal())
return false; // Cannot inline an indirect call... or external function.
// Don't inline a recursive call.
const Function *Caller = CI->getParent()->getParent();
if (Caller == Callee) return false;
// InlineQuality - This value measures how good of an inline candidate this
// call site is to inline. The initial value determines how aggressive the
// inliner is. If this value is negative after the final computation,
// inlining is not performed.
//
int InlineQuality = 200; // FIXME: This is VERY conservative
// If there is only one call of the function, and it has internal linkage,
// make it almost guaranteed to be inlined.
//
if (Callee->use_size() == 1 && Callee->hasInternalLinkage())
InlineQuality += 30000;
// Add to the inline quality for properties that make the call valueable 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.
//
for (User::const_op_iterator I = CI->op_begin()+1, E = CI->op_end();
I != E; ++I){
// 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.
InlineQuality += 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))
InlineQuality += 100;
// If a constant, global variable or alloca is passed in, inlining this
// function is likely to allow significant future optimization possibilities
// (constant propagation, scalar promotion, and scalarization), so encourage
// the inlining of the function.
//
else if (isa<Constant>(I) || isa<GlobalVariable>(I) || isa<AllocaInst>(I))
InlineQuality += 60;
}
// 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.
// As soon as the inline quality gets negative, bail out.
// Look at the size of the callee. Each basic block counts as 20 units, and
// each instruction counts as 10.
for (Function::const_iterator BB = Callee->begin(), E = Callee->end();
BB != E; ++BB) {
InlineQuality -= BB->size()*10 + 20;
if (InlineQuality < 0) return false;
}
// Don't inline into something too big, which would make it bigger. Here, we
// count each basic block as a single unit.
for (Function::const_iterator BB = Caller->begin(), E = Caller->end();
BB != E; ++BB) {
--InlineQuality;
if (InlineQuality < 0) return false;
}
// If we get here, this call site is high enough "quality" to inline.
DEBUG(std::cerr << "Inlining in '" << Caller->getName()
<< "', quality = " << InlineQuality << ": " << *CI);
return true;
}
// doInlining - Use a heuristic based approach to inline functions that seem to
// look good.
//
bool FunctionInlining::doInlining(Function *F) {
// If we have already processed this function (ie, it is recursive) don't
// revisit.
std::set<Function*>::iterator PFI = ProcessedFunctions.lower_bound(F);
if (PFI != ProcessedFunctions.end() && *PFI == F) return false;
// Insert the function in the set so it doesn't get revisited.
ProcessedFunctions.insert(PFI, F);
bool Changed = false;
for (Function::iterator BB = F->begin(); BB != F->end(); ++BB)
for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
bool ShouldInc = true;
// Found a call instruction? FIXME: This should also handle INVOKEs
if (CallInst *CI = dyn_cast<CallInst>(I)) {
if (Function *Callee = CI->getCalledFunction())
doInlining(Callee); // Inline in callees before callers!
// Decide whether we should inline this function...
if (ShouldInlineFunction(CI)) {
// Save an iterator to the instruction before the call if it exists,
// otherwise get an iterator at the end of the block... because the
// call will be destroyed.
//
BasicBlock::iterator SI;
if (I != BB->begin()) {
SI = I; --SI; // Instruction before the call...
} else {
SI = BB->end();
}
// Attempt to inline the function...
if (InlineFunction(CI)) {
++NumInlined;
Changed = true;
// Move to instruction before the call...
I = (SI == BB->end()) ? BB->begin() : SI;
ShouldInc = false; // Don't increment iterator until next time
}
}
}
if (ShouldInc) ++I;
}
return Changed;
}

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lib/Transforms/Utils/InlineFunction.cpp Normal file
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@ -0,0 +1,164 @@
//===- InlineFunction.cpp - Code to perform function inlining -------------===//
//
// This file implements inlining of a function into a call site, resolving
// parameters and the return value as appropriate.
//
// FIXME: This pass should transform alloca instructions in the called function
// into malloc/free pairs! Or perhaps it should refuse to inline them!
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Module.h"
#include "llvm/iTerminators.h"
#include "llvm/iPHINode.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/DerivedTypes.h"
// InlineFunction - This function inlines the called function into the basic
// block of the caller. This returns false if it is not possible to inline this
// call. The program is still in a well defined state if this occurs though.
//
// Note that this only does one level of inlining. For example, if the
// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
// exists in the instruction stream. Similiarly this will inline a recursive
// function by one level.
//
bool InlineFunction(CallInst *CI) {
assert(isa<CallInst>(CI) && "InlineFunction only works on CallInst nodes");
assert(CI->getParent() && "Instruction not embedded in basic block!");
assert(CI->getParent()->getParent() && "Instruction not in function!");
const Function *CalledFunc = CI->getCalledFunction();
if (CalledFunc == 0 || // Can't inline external function or indirect
CalledFunc->isExternal() || // call, or call to a vararg function!
CalledFunc->getFunctionType()->isVarArg()) return false;
BasicBlock *OrigBB = CI->getParent();
Function *Caller = OrigBB->getParent();
// Call splitBasicBlock - The original basic block now ends at the instruction
// immediately before the call. The original basic block now ends with an
// unconditional branch to NewBB, and NewBB starts with the call instruction.
//
BasicBlock *NewBB = OrigBB->splitBasicBlock(CI);
NewBB->setName(OrigBB->getName()+".split");
// Remove (unlink) the CallInst from the start of the new basic block.
NewBB->getInstList().remove(CI);
// If we have a return value generated by this call, convert it into a PHI
// node that gets values from each of the old RET instructions in the original
// function.
//
PHINode *PHI = 0;
if (!CI->use_empty()) {
// The PHI node should go at the front of the new basic block to merge all
// possible incoming values.
//
PHI = new PHINode(CalledFunc->getReturnType(), CI->getName(),
NewBB->begin());
// Anything that used the result of the function call should now use the PHI
// node as their operand.
//
CI->replaceAllUsesWith(PHI);
}
// Get an iterator to the last basic block in the function, which will have
// the new function inlined after it.
//
Function::iterator LastBlock = &Caller->back();
// Calculate the vector of arguments to pass into the function cloner...
std::map<const Value*, Value*> ValueMap;
assert((unsigned)std::distance(CalledFunc->abegin(), CalledFunc->aend()) ==
CI->getNumOperands()-1 && "No varargs calls can be inlined yet!");
unsigned i = 1;
for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend();
I != E; ++I, ++i)
ValueMap[I] = CI->getOperand(i);
// Since we are now done with the CallInst, we can delete it.
delete CI;
// Make a vector to capture the return instructions in the cloned function...
std::vector<ReturnInst*> Returns;
// Populate the value map with all of the globals in the program.
Module &M = *Caller->getParent();
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
ValueMap[I] = I;
for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
ValueMap[I] = I;
// Do all of the hard part of cloning the callee into the caller...
CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
// Loop over all of the return instructions, turning them into unconditional
// branches to the merge point now...
for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
ReturnInst *RI = Returns[i];
BasicBlock *BB = RI->getParent();
// Add a branch to the merge point where the PHI node would live...
new BranchInst(NewBB, RI);
if (PHI) { // The PHI node should include this value!
assert(RI->getReturnValue() && "Ret should have value!");
assert(RI->getReturnValue()->getType() == PHI->getType() &&
"Ret value not consistent in function!");
PHI->addIncoming(RI->getReturnValue(), BB);
}
// Delete the return instruction now
BB->getInstList().erase(RI);
}
// Check to see if the PHI node only has one argument. This is a common
// case resulting from there only being a single return instruction in the
// function call. Because this is so common, eliminate the PHI node.
//
if (PHI && PHI->getNumIncomingValues() == 1) {
PHI->replaceAllUsesWith(PHI->getIncomingValue(0));
PHI->getParent()->getInstList().erase(PHI);
}
// Change the branch that used to go to NewBB to branch to the first basic
// block of the inlined function.
//
TerminatorInst *Br = OrigBB->getTerminator();
assert(Br && Br->getOpcode() == Instruction::Br &&
"splitBasicBlock broken!");
Br->setOperand(0, ++LastBlock);
// If there are any alloca instructions in the block that used to be the entry
// block for the callee, move them to the entry block of the caller. First
// calculate which instruction they should be inserted before. We insert the
// instructions at the end of the current alloca list.
//
BasicBlock::iterator InsertPoint = Caller->begin()->begin();
while (isa<AllocaInst>(InsertPoint)) ++InsertPoint;
for (BasicBlock::iterator I = LastBlock->begin(), E = LastBlock->end();
I != E; )
if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
++I; // Move to the next instruction
LastBlock->getInstList().remove(AI);
Caller->front().getInstList().insert(InsertPoint, AI);
} else {
++I;
}
// Now that the function is correct, make it a little bit nicer. In
// particular, move the basic blocks inserted from the end of the function
// into the space made by splitting the source basic block.
//
Caller->getBasicBlockList().splice(NewBB, Caller->getBasicBlockList(),
LastBlock, Caller->end());
return true;
}