mirror of
https://github.com/opnsense/src.git
synced 2026-03-12 13:42:37 -04:00
f785676f2a
all of the features in the current working draft of the upcoming C++ standard, provisionally named C++1y. The code generator's performance is greatly increased, and the loop auto-vectorizer is now enabled at -Os and -O2 in addition to -O3. The PowerPC backend has made several major improvements to code generation quality and compile time, and the X86, SPARC, ARM32, Aarch64 and SystemZ backends have all seen major feature work. Release notes for llvm and clang can be found here: <http://llvm.org/releases/3.4/docs/ReleaseNotes.html> <http://llvm.org/releases/3.4/tools/clang/docs/ReleaseNotes.html> MFC after: 1 month
97 lines
3.3 KiB
C++
97 lines
3.3 KiB
C++
//===- DCE.cpp - Code to perform dead code elimination --------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the Aggressive Dead Code Elimination pass. This pass
|
|
// optimistically assumes that all instructions are dead until proven otherwise,
|
|
// allowing it to eliminate dead computations that other DCE passes do not
|
|
// catch, particularly involving loop computations.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "adce"
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/ADT/DepthFirstIterator.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
#include "llvm/ADT/SmallVector.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/IR/BasicBlock.h"
|
|
#include "llvm/IR/Instructions.h"
|
|
#include "llvm/IR/IntrinsicInst.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Support/CFG.h"
|
|
#include "llvm/Support/InstIterator.h"
|
|
using namespace llvm;
|
|
|
|
STATISTIC(NumRemoved, "Number of instructions removed");
|
|
|
|
namespace {
|
|
struct ADCE : public FunctionPass {
|
|
static char ID; // Pass identification, replacement for typeid
|
|
ADCE() : FunctionPass(ID) {
|
|
initializeADCEPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
virtual bool runOnFunction(Function& F);
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage& AU) const {
|
|
AU.setPreservesCFG();
|
|
}
|
|
|
|
};
|
|
}
|
|
|
|
char ADCE::ID = 0;
|
|
INITIALIZE_PASS(ADCE, "adce", "Aggressive Dead Code Elimination", false, false)
|
|
|
|
bool ADCE::runOnFunction(Function& F) {
|
|
SmallPtrSet<Instruction*, 128> alive;
|
|
SmallVector<Instruction*, 128> worklist;
|
|
|
|
// Collect the set of "root" instructions that are known live.
|
|
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
|
|
if (isa<TerminatorInst>(I.getInstructionIterator()) ||
|
|
isa<DbgInfoIntrinsic>(I.getInstructionIterator()) ||
|
|
isa<LandingPadInst>(I.getInstructionIterator()) ||
|
|
I->mayHaveSideEffects()) {
|
|
alive.insert(I.getInstructionIterator());
|
|
worklist.push_back(I.getInstructionIterator());
|
|
}
|
|
|
|
// Propagate liveness backwards to operands.
|
|
while (!worklist.empty()) {
|
|
Instruction* curr = worklist.pop_back_val();
|
|
for (Instruction::op_iterator OI = curr->op_begin(), OE = curr->op_end();
|
|
OI != OE; ++OI)
|
|
if (Instruction* Inst = dyn_cast<Instruction>(OI))
|
|
if (alive.insert(Inst))
|
|
worklist.push_back(Inst);
|
|
}
|
|
|
|
// The inverse of the live set is the dead set. These are those instructions
|
|
// which have no side effects and do not influence the control flow or return
|
|
// value of the function, and may therefore be deleted safely.
|
|
// NOTE: We reuse the worklist vector here for memory efficiency.
|
|
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
|
|
if (!alive.count(I.getInstructionIterator())) {
|
|
worklist.push_back(I.getInstructionIterator());
|
|
I->dropAllReferences();
|
|
}
|
|
|
|
for (SmallVectorImpl<Instruction *>::iterator I = worklist.begin(),
|
|
E = worklist.end(); I != E; ++I) {
|
|
++NumRemoved;
|
|
(*I)->eraseFromParent();
|
|
}
|
|
|
|
return !worklist.empty();
|
|
}
|
|
|
|
FunctionPass *llvm::createAggressiveDCEPass() {
|
|
return new ADCE();
|
|
}
|