mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-17 03:30:28 +00:00
551ccae044
Move include/Config and include/Support into include/llvm/Config, include/llvm/ADT and include/llvm/Support. From here on out, all LLVM public header files must be under include/llvm/. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16137 91177308-0d34-0410-b5e6-96231b3b80d8
105 lines
3.2 KiB
C++
105 lines
3.2 KiB
C++
//===- SimplifyCFG.cpp - CFG Simplification Pass --------------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file was developed by the LLVM research group and is distributed under
|
|
// the University of Illinois Open Source License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements dead code elimination and basic block merging.
|
|
//
|
|
// Specifically, this:
|
|
// * removes basic blocks with no predecessors
|
|
// * merges a basic block into its predecessor if there is only one and the
|
|
// predecessor only has one successor.
|
|
// * Eliminates PHI nodes for basic blocks with a single predecessor
|
|
// * Eliminates a basic block that only contains an unconditional branch
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Transforms/Utils/Local.h"
|
|
#include "llvm/Module.h"
|
|
#include "llvm/Support/CFG.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include <set>
|
|
using namespace llvm;
|
|
|
|
namespace {
|
|
Statistic<> NumSimpl("cfgsimplify", "Number of blocks simplified");
|
|
|
|
struct CFGSimplifyPass : public FunctionPass {
|
|
virtual bool runOnFunction(Function &F);
|
|
};
|
|
RegisterOpt<CFGSimplifyPass> X("simplifycfg", "Simplify the CFG");
|
|
}
|
|
|
|
// Public interface to the CFGSimplification pass
|
|
FunctionPass *llvm::createCFGSimplificationPass() {
|
|
return new CFGSimplifyPass();
|
|
}
|
|
|
|
static bool MarkAliveBlocks(BasicBlock *BB, std::set<BasicBlock*> &Reachable) {
|
|
if (Reachable.count(BB)) return false;
|
|
Reachable.insert(BB);
|
|
|
|
bool Changed = ConstantFoldTerminator(BB);
|
|
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
|
|
MarkAliveBlocks(*SI, Reachable);
|
|
|
|
return Changed;
|
|
}
|
|
|
|
|
|
// It is possible that we may require multiple passes over the code to fully
|
|
// simplify the CFG.
|
|
//
|
|
bool CFGSimplifyPass::runOnFunction(Function &F) {
|
|
std::set<BasicBlock*> Reachable;
|
|
bool Changed = MarkAliveBlocks(F.begin(), Reachable);
|
|
|
|
// If there are unreachable blocks in the CFG...
|
|
if (Reachable.size() != F.size()) {
|
|
assert(Reachable.size() < F.size());
|
|
NumSimpl += F.size()-Reachable.size();
|
|
|
|
// Loop over all of the basic blocks that are not reachable, dropping all of
|
|
// their internal references...
|
|
for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB)
|
|
if (!Reachable.count(BB)) {
|
|
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI!=SE; ++SI)
|
|
if (Reachable.count(*SI))
|
|
(*SI)->removePredecessor(BB);
|
|
BB->dropAllReferences();
|
|
}
|
|
|
|
for (Function::iterator I = ++F.begin(); I != F.end();)
|
|
if (!Reachable.count(I))
|
|
I = F.getBasicBlockList().erase(I);
|
|
else
|
|
++I;
|
|
|
|
Changed = true;
|
|
}
|
|
|
|
bool LocalChange = true;
|
|
while (LocalChange) {
|
|
LocalChange = false;
|
|
|
|
// Loop over all of the basic blocks (except the first one) and remove them
|
|
// if they are unneeded...
|
|
//
|
|
for (Function::iterator BBIt = ++F.begin(); BBIt != F.end(); ) {
|
|
if (SimplifyCFG(BBIt++)) {
|
|
LocalChange = true;
|
|
++NumSimpl;
|
|
}
|
|
}
|
|
Changed |= LocalChange;
|
|
}
|
|
|
|
return Changed;
|
|
}
|