[llvm-commits] CVS: llvm/lib/Transforms/IPO/FunctionInlining.cpp
Chris Lattner
lattner at cs.uiuc.edu
Thu May 29 10:12:06 PDT 2003
Changes in directory llvm/lib/Transforms/IPO:
FunctionInlining.cpp updated: 1.44 -> 1.45
---
Log message:
* Separate all of the grunt work of inlining out into the Utils library.
* Make the function inliner _significantly_ smarter. :)
---
Diffs of the changes:
Index: llvm/lib/Transforms/IPO/FunctionInlining.cpp
diff -u llvm/lib/Transforms/IPO/FunctionInlining.cpp:1.44 llvm/lib/Transforms/IPO/FunctionInlining.cpp:1.45
--- llvm/lib/Transforms/IPO/FunctionInlining.cpp:1.44 Wed May 7 21:36:43 2003
+++ llvm/lib/Transforms/IPO/FunctionInlining.cpp Thu May 29 10:11:31 2003
@@ -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>
+#include <set>
-static Statistic<> NumInlined("inline", "Number of functions inlined");
+namespace {
+ 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");
+ 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;
+ }
- // Remove (unlink) the CallInst from the start of the new basic block.
- NewBB->getInstList().remove(CI);
+ private:
+ std::set<Function*> ProcessedFunctions; // Prevent infinite recursion
+ bool doInlining(Function *F);
+ };
+ RegisterOpt<FunctionInlining> X("inline", "Function Integration/Inlining");
+}
- // 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());
+Pass *createFunctionInliningPass() { return new FunctionInlining(); }
- // 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();
+// 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!");
- // 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);
- }
+ const Function *Callee = CI->getCalledFunction();
+ if (Callee == 0 || Callee->isExternal())
+ return false; // Cannot inline an indirect call... or external function.
- // Delete the return instruction now
- BB->getInstList().erase(RI);
- }
+ // Don't inline a recursive call.
+ const Function *Caller = CI->getParent()->getParent();
+ if (Caller == Callee) return false;
- // 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.
+ // 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.
//
- if (PHI && PHI->getNumIncomingValues() == 1) {
- PHI->replaceAllUsesWith(PHI->getIncomingValue(0));
- PHI->getParent()->getInstList().erase(PHI);
- }
+ int InlineQuality = 200; // FIXME: This is VERY conservative
- // Change the branch that used to go to NewBB to branch to the first basic
- // block of the inlined function.
+ // If there is only one call of the function, and it has internal linkage,
+ // make it almost guaranteed to be inlined.
//
- TerminatorInst *Br = OrigBB->getTerminator();
- assert(Br && Br->getOpcode() == Instruction::Br &&
- "splitBasicBlock broken!");
- Br->setOperand(0, ++LastBlock);
- return true;
-}
+ if (Callee->use_size() == 1 && Callee->hasInternalLinkage())
+ InlineQuality += 30000;
-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;
+ // 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;
+ }
- // Don't inline something too big. This is a really crappy heuristic
- if (F->size() > 3) return false;
+ // 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. This is a **really** crappy heuristic
- if (CI->getParent()->getParent()->size() > 10) 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;
+ }
- // Go ahead and try just about anything else.
+ // 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;
}
-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.
+// doInlining - Use a heuristic based approach to inline functions that seem to
+// look good.
//
-static bool doFunctionInlining(Function &F) {
- bool Changed = false;
+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);
- // 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;
+ 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;
}
-namespace {
- struct FunctionInlining : public FunctionPass {
- virtual bool runOnFunction(Function &F) {
- return doFunctionInlining(F);
- }
- };
- RegisterOpt<FunctionInlining> X("inline", "Function Integration/Inlining");
-}
-
-Pass *createFunctionInliningPass() { return new FunctionInlining(); }
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