llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
Misha Brukman 5560c9d49c Spell `necessary' correctly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7944 91177308-0d34-0410-b5e6-96231b3b80d8
2003-08-18 14:43:39 +00:00

108 lines
3.9 KiB
C++

//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
//
// This family of functions perform manipulations on basic blocks, and
// instructions contained within basic blocks.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Function.h"
#include "llvm/iTerminators.h"
#include "llvm/Constant.h"
#include "llvm/Type.h"
#include <algorithm>
// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
// with a value, then remove and delete the original instruction.
//
void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Value *V) {
Instruction &I = *BI;
// Replaces all of the uses of the instruction with uses of the value
I.replaceAllUsesWith(V);
std::string OldName = I.getName();
// Delete the unnecessary instruction now...
BI = BIL.erase(BI);
// Make sure to propagate a name if there is one already...
if (OldName.size() && !V->hasName())
V->setName(OldName, &BIL.getParent()->getSymbolTable());
}
// ReplaceInstWithInst - Replace the instruction specified by BI with the
// instruction specified by I. The original instruction is deleted and BI is
// updated to point to the new instruction.
//
void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Instruction *I) {
assert(I->getParent() == 0 &&
"ReplaceInstWithInst: Instruction already inserted into basic block!");
// Insert the new instruction into the basic block...
BasicBlock::iterator New = BIL.insert(BI, I);
// Replace all uses of the old instruction, and delete it.
ReplaceInstWithValue(BIL, BI, I);
// Move BI back to point to the newly inserted instruction
BI = New;
}
// ReplaceInstWithInst - Replace the instruction specified by From with the
// instruction specified by To.
//
void ReplaceInstWithInst(Instruction *From, Instruction *To) {
BasicBlock::iterator BI(From);
ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
}
// RemoveSuccessor - Change the specified terminator instruction such that its
// successor #SuccNum no longer exists. Because this reduces the outgoing
// degree of the current basic block, the actual terminator instruction itself
// may have to be changed. In the case where the last successor of the block is
// deleted, a return instruction is inserted in its place which can cause a
// suprising change in program behavior if it is not expected.
//
void RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
assert(SuccNum < TI->getNumSuccessors() &&
"Trying to remove a nonexistant successor!");
// If our old successor block contains any PHI nodes, remove the entry in the
// PHI nodes that comes from this branch...
//
BasicBlock *BB = TI->getParent();
TI->getSuccessor(SuccNum)->removePredecessor(BB);
TerminatorInst *NewTI = 0;
switch (TI->getOpcode()) {
case Instruction::Br:
// If this is a conditional branch... convert to unconditional branch.
if (TI->getNumSuccessors() == 2) {
cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum));
} else { // Otherwise convert to a return instruction...
Value *RetVal = 0;
// Create a value to return... if the function doesn't return null...
if (BB->getParent()->getReturnType() != Type::VoidTy)
RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
// Create the return...
NewTI = new ReturnInst(RetVal);
}
break;
case Instruction::Invoke: // Should convert to call
case Instruction::Switch: // Should remove entry
default:
case Instruction::Ret: // Cannot happen, has no successors!
assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!");
abort();
}
if (NewTI) // If it's a different instruction, replace.
ReplaceInstWithInst(TI, NewTI);
}