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* Make the function inliner _significantly_ smarter. :) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6396 91177308-0d34-0410-b5e6-96231b3b80d8
165 lines
6.4 KiB
C++
165 lines
6.4 KiB
C++
//===- InlineFunction.cpp - Code to perform function inlining -------------===//
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//
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// This file implements inlining of a function into a call site, resolving
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// parameters and the return value as appropriate.
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//
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// FIXME: This pass should transform alloca instructions in the called function
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// into malloc/free pairs! Or perhaps it should refuse to inline them!
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Module.h"
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#include "llvm/iTerminators.h"
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#include "llvm/iPHINode.h"
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#include "llvm/iMemory.h"
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#include "llvm/iOther.h"
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#include "llvm/DerivedTypes.h"
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// InlineFunction - This function inlines the called function into the basic
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// block of the caller. This returns false if it is not possible to inline this
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// call. The program is still in a well defined state if this occurs though.
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//
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// Note that this only does one level of inlining. For example, if the
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// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
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// exists in the instruction stream. Similiarly this will inline a recursive
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// function by one level.
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//
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bool InlineFunction(CallInst *CI) {
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assert(isa<CallInst>(CI) && "InlineFunction only works on CallInst nodes");
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assert(CI->getParent() && "Instruction not embedded in basic block!");
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assert(CI->getParent()->getParent() && "Instruction not in function!");
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const Function *CalledFunc = CI->getCalledFunction();
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if (CalledFunc == 0 || // Can't inline external function or indirect
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CalledFunc->isExternal() || // call, or call to a vararg function!
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CalledFunc->getFunctionType()->isVarArg()) return false;
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BasicBlock *OrigBB = CI->getParent();
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Function *Caller = OrigBB->getParent();
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// Call splitBasicBlock - The original basic block now ends at the instruction
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// immediately before the call. The original basic block now ends with an
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// unconditional branch to NewBB, and NewBB starts with the call instruction.
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//
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BasicBlock *NewBB = OrigBB->splitBasicBlock(CI);
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NewBB->setName(OrigBB->getName()+".split");
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// Remove (unlink) the CallInst from the start of the new basic block.
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NewBB->getInstList().remove(CI);
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// If we have a return value generated by this call, convert it into a PHI
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// node that gets values from each of the old RET instructions in the original
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// function.
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//
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PHINode *PHI = 0;
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if (!CI->use_empty()) {
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// The PHI node should go at the front of the new basic block to merge all
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// possible incoming values.
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//
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PHI = new PHINode(CalledFunc->getReturnType(), CI->getName(),
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NewBB->begin());
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// Anything that used the result of the function call should now use the PHI
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// node as their operand.
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//
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CI->replaceAllUsesWith(PHI);
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}
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// Get an iterator to the last basic block in the function, which will have
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// the new function inlined after it.
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//
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Function::iterator LastBlock = &Caller->back();
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// Calculate the vector of arguments to pass into the function cloner...
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std::map<const Value*, Value*> ValueMap;
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assert((unsigned)std::distance(CalledFunc->abegin(), CalledFunc->aend()) ==
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CI->getNumOperands()-1 && "No varargs calls can be inlined yet!");
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unsigned i = 1;
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for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend();
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I != E; ++I, ++i)
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ValueMap[I] = CI->getOperand(i);
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// Since we are now done with the CallInst, we can delete it.
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delete CI;
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// Make a vector to capture the return instructions in the cloned function...
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std::vector<ReturnInst*> Returns;
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// Populate the value map with all of the globals in the program.
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Module &M = *Caller->getParent();
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
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ValueMap[I] = I;
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for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
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ValueMap[I] = I;
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// Do all of the hard part of cloning the callee into the caller...
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CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
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// Loop over all of the return instructions, turning them into unconditional
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// branches to the merge point now...
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for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
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ReturnInst *RI = Returns[i];
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BasicBlock *BB = RI->getParent();
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// Add a branch to the merge point where the PHI node would live...
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new BranchInst(NewBB, RI);
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if (PHI) { // The PHI node should include this value!
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assert(RI->getReturnValue() && "Ret should have value!");
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assert(RI->getReturnValue()->getType() == PHI->getType() &&
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"Ret value not consistent in function!");
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PHI->addIncoming(RI->getReturnValue(), BB);
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}
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// Delete the return instruction now
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BB->getInstList().erase(RI);
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}
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// Check to see if the PHI node only has one argument. This is a common
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// case resulting from there only being a single return instruction in the
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// function call. Because this is so common, eliminate the PHI node.
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//
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if (PHI && PHI->getNumIncomingValues() == 1) {
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PHI->replaceAllUsesWith(PHI->getIncomingValue(0));
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PHI->getParent()->getInstList().erase(PHI);
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}
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// Change the branch that used to go to NewBB to branch to the first basic
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// block of the inlined function.
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//
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TerminatorInst *Br = OrigBB->getTerminator();
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assert(Br && Br->getOpcode() == Instruction::Br &&
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"splitBasicBlock broken!");
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Br->setOperand(0, ++LastBlock);
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// If there are any alloca instructions in the block that used to be the entry
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// block for the callee, move them to the entry block of the caller. First
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// calculate which instruction they should be inserted before. We insert the
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// instructions at the end of the current alloca list.
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//
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BasicBlock::iterator InsertPoint = Caller->begin()->begin();
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while (isa<AllocaInst>(InsertPoint)) ++InsertPoint;
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for (BasicBlock::iterator I = LastBlock->begin(), E = LastBlock->end();
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I != E; )
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if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
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++I; // Move to the next instruction
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LastBlock->getInstList().remove(AI);
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Caller->front().getInstList().insert(InsertPoint, AI);
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} else {
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++I;
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}
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// Now that the function is correct, make it a little bit nicer. In
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// particular, move the basic blocks inserted from the end of the function
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// into the space made by splitting the source basic block.
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//
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Caller->getBasicBlockList().splice(NewBB, Caller->getBasicBlockList(),
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LastBlock, Caller->end());
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return true;
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}
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