125e9405272630204eb721d8b6ab47a5a25f24885Owen Anderson//===- CorrelatedValuePropagation.cpp - Propagate CFG-derived info --------===//
2a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//
3a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//                     The LLVM Compiler Infrastructure
4a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//
5a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson// This file is distributed under the University of Illinois Open Source
6a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson// License. See LICENSE.TXT for details.
7a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//
8a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//===----------------------------------------------------------------------===//
9a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//
1025e9405272630204eb721d8b6ab47a5a25f24885Owen Anderson// This file implements the Correlated Value Propagation pass.
11a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//
12a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson//===----------------------------------------------------------------------===//
13a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson
1425e9405272630204eb721d8b6ab47a5a25f24885Owen Anderson#define DEBUG_TYPE "correlated-value-propagation"
15a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson#include "llvm/Transforms/Scalar.h"
16562b84b3aea359d1f918184e355da82bf05eb290Jay Foad#include "llvm/Constants.h"
17a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson#include "llvm/Function.h"
18a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson#include "llvm/Instructions.h"
19a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson#include "llvm/Pass.h"
20cdbd99262286e96729007ac535cd430ecb3d38acDuncan Sands#include "llvm/Analysis/InstructionSimplify.h"
21a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson#include "llvm/Analysis/LazyValueInfo.h"
22597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson#include "llvm/Support/CFG.h"
23a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson#include "llvm/Transforms/Utils/Local.h"
24f523b3e0878ea47e72b7d880b8fd18a33636fbdeOwen Anderson#include "llvm/ADT/Statistic.h"
25a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Andersonusing namespace llvm;
26a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson
271593dd6779d7ab1db13c44f32f987c32aff2b54bOwen AndersonSTATISTIC(NumPhis,      "Number of phis propagated");
281593dd6779d7ab1db13c44f32f987c32aff2b54bOwen AndersonSTATISTIC(NumSelects,   "Number of selects propagated");
291593dd6779d7ab1db13c44f32f987c32aff2b54bOwen AndersonSTATISTIC(NumMemAccess, "Number of memory access targets propagated");
30597dad35b8b86c076dbbb0d095319c79de7806caOwen AndersonSTATISTIC(NumCmps,      "Number of comparisons propagated");
31a8eb6bb408e84ceb468ceb409f4c87308e67b9ebDuncan SandsSTATISTIC(NumDeadCases, "Number of switch cases removed");
32f523b3e0878ea47e72b7d880b8fd18a33636fbdeOwen Anderson
33a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Andersonnamespace {
3425e9405272630204eb721d8b6ab47a5a25f24885Owen Anderson  class CorrelatedValuePropagation : public FunctionPass {
35a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    LazyValueInfo *LVI;
3693f83deba1df95211898fe756758e81969955bd9Owen Anderson
37a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    bool processSelect(SelectInst *SI);
38a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    bool processPHI(PHINode *P);
391593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson    bool processMemAccess(Instruction *I);
40597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson    bool processCmp(CmpInst *C);
416f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    bool processSwitch(SwitchInst *SI);
4293f83deba1df95211898fe756758e81969955bd9Owen Anderson
43a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  public:
44a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    static char ID;
45081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson    CorrelatedValuePropagation(): FunctionPass(ID) {
46081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson     initializeCorrelatedValuePropagationPass(*PassRegistry::getPassRegistry());
47081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson    }
4893f83deba1df95211898fe756758e81969955bd9Owen Anderson
49a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    bool runOnFunction(Function &F);
5093f83deba1df95211898fe756758e81969955bd9Owen Anderson
51a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
52a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson      AU.addRequired<LazyValueInfo>();
53a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    }
54a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  };
55a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson}
56a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson
5725e9405272630204eb721d8b6ab47a5a25f24885Owen Andersonchar CorrelatedValuePropagation::ID = 0;
582ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_BEGIN(CorrelatedValuePropagation, "correlated-propagation",
592ab36d350293c77fc8941ce1023e4899df7e3a82Owen Anderson                "Value Propagation", false, false)
602ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(LazyValueInfo)
612ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_END(CorrelatedValuePropagation, "correlated-propagation",
62ce665bd2e2b581ab0858d1afe359192bac96b868Owen Anderson                "Value Propagation", false, false)
63a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson
64a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson// Public interface to the Value Propagation pass
6525e9405272630204eb721d8b6ab47a5a25f24885Owen AndersonPass *llvm::createCorrelatedValuePropagationPass() {
6625e9405272630204eb721d8b6ab47a5a25f24885Owen Anderson  return new CorrelatedValuePropagation();
67a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson}
68a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson
6925e9405272630204eb721d8b6ab47a5a25f24885Owen Andersonbool CorrelatedValuePropagation::processSelect(SelectInst *S) {
70a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson  if (S->getType()->isVectorTy()) return false;
711593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  if (isa<Constant>(S->getOperand(0))) return false;
7293f83deba1df95211898fe756758e81969955bd9Owen Anderson
73a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  Constant *C = LVI->getConstant(S->getOperand(0), S->getParent());
74a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  if (!C) return false;
7593f83deba1df95211898fe756758e81969955bd9Owen Anderson
76a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  ConstantInt *CI = dyn_cast<ConstantInt>(C);
77a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  if (!CI) return false;
7893f83deba1df95211898fe756758e81969955bd9Owen Anderson
7986e8a700f516e8993417fb57d5386614b35c775dOwen Anderson  Value *ReplaceWith = S->getOperand(1);
8086e8a700f516e8993417fb57d5386614b35c775dOwen Anderson  Value *Other = S->getOperand(2);
8186e8a700f516e8993417fb57d5386614b35c775dOwen Anderson  if (!CI->isOne()) std::swap(ReplaceWith, Other);
8286e8a700f516e8993417fb57d5386614b35c775dOwen Anderson  if (ReplaceWith == S) ReplaceWith = UndefValue::get(S->getType());
8386e8a700f516e8993417fb57d5386614b35c775dOwen Anderson
8486e8a700f516e8993417fb57d5386614b35c775dOwen Anderson  S->replaceAllUsesWith(ReplaceWith);
85a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson  S->eraseFromParent();
86a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson
87f523b3e0878ea47e72b7d880b8fd18a33636fbdeOwen Anderson  ++NumSelects;
8893f83deba1df95211898fe756758e81969955bd9Owen Anderson
89a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  return true;
90a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson}
91a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson
9225e9405272630204eb721d8b6ab47a5a25f24885Owen Andersonbool CorrelatedValuePropagation::processPHI(PHINode *P) {
93a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson  bool Changed = false;
9493f83deba1df95211898fe756758e81969955bd9Owen Anderson
95a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  BasicBlock *BB = P->getParent();
96a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson  for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) {
97a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson    Value *Incoming = P->getIncomingValue(i);
98a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson    if (isa<Constant>(Incoming)) continue;
9993f83deba1df95211898fe756758e81969955bd9Owen Anderson
100a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    Constant *C = LVI->getConstantOnEdge(P->getIncomingValue(i),
101a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson                                         P->getIncomingBlock(i),
102a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson                                         BB);
103a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson    if (!C) continue;
10493f83deba1df95211898fe756758e81969955bd9Owen Anderson
105a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    P->setIncomingValue(i, C);
106a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson    Changed = true;
107a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  }
108cdbd99262286e96729007ac535cd430ecb3d38acDuncan Sands
109cdbd99262286e96729007ac535cd430ecb3d38acDuncan Sands  if (Value *V = SimplifyInstruction(P)) {
110cdbd99262286e96729007ac535cd430ecb3d38acDuncan Sands    P->replaceAllUsesWith(V);
111a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    P->eraseFromParent();
112a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson    Changed = true;
113a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  }
114cdbd99262286e96729007ac535cd430ecb3d38acDuncan Sands
115a8eb6bb408e84ceb468ceb409f4c87308e67b9ebDuncan Sands  if (Changed)
116a8eb6bb408e84ceb468ceb409f4c87308e67b9ebDuncan Sands    ++NumPhis;
11793f83deba1df95211898fe756758e81969955bd9Owen Anderson
118a081d15b842e87c670260006eb17b5c1a826b5eeOwen Anderson  return Changed;
119a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson}
120a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson
1211593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Andersonbool CorrelatedValuePropagation::processMemAccess(Instruction *I) {
1221593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  Value *Pointer = 0;
1231593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  if (LoadInst *L = dyn_cast<LoadInst>(I))
1241593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson    Pointer = L->getPointerOperand();
1251593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  else
1261593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson    Pointer = cast<StoreInst>(I)->getPointerOperand();
12793f83deba1df95211898fe756758e81969955bd9Owen Anderson
1281593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  if (isa<Constant>(Pointer)) return false;
12993f83deba1df95211898fe756758e81969955bd9Owen Anderson
1301593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  Constant *C = LVI->getConstant(Pointer, I->getParent());
1311593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  if (!C) return false;
13293f83deba1df95211898fe756758e81969955bd9Owen Anderson
1331593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  ++NumMemAccess;
1341593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  I->replaceUsesOfWith(Pointer, C);
1351593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson  return true;
1361593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson}
1371593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson
138597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson/// processCmp - If the value of this comparison could be determined locally,
139597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson/// constant propagation would already have figured it out.  Instead, walk
140597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson/// the predecessors and statically evaluate the comparison based on information
141597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson/// available on that edge.  If a given static evaluation is true on ALL
142597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson/// incoming edges, then it's true universally and we can simplify the compare.
143597dad35b8b86c076dbbb0d095319c79de7806caOwen Andersonbool CorrelatedValuePropagation::processCmp(CmpInst *C) {
144597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  Value *Op0 = C->getOperand(0);
145597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  if (isa<Instruction>(Op0) &&
146597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson      cast<Instruction>(Op0)->getParent() == C->getParent())
147597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson    return false;
14893f83deba1df95211898fe756758e81969955bd9Owen Anderson
149597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  Constant *Op1 = dyn_cast<Constant>(C->getOperand(1));
150597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  if (!Op1) return false;
15193f83deba1df95211898fe756758e81969955bd9Owen Anderson
152597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  pred_iterator PI = pred_begin(C->getParent()), PE = pred_end(C->getParent());
153597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  if (PI == PE) return false;
15493f83deba1df95211898fe756758e81969955bd9Owen Anderson
15593f83deba1df95211898fe756758e81969955bd9Owen Anderson  LazyValueInfo::Tristate Result = LVI->getPredicateOnEdge(C->getPredicate(),
156597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson                                    C->getOperand(0), Op1, *PI, C->getParent());
157597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  if (Result == LazyValueInfo::Unknown) return false;
158597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson
159597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  ++PI;
160597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  while (PI != PE) {
16193f83deba1df95211898fe756758e81969955bd9Owen Anderson    LazyValueInfo::Tristate Res = LVI->getPredicateOnEdge(C->getPredicate(),
162597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson                                    C->getOperand(0), Op1, *PI, C->getParent());
163597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson    if (Res != Result) return false;
164597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson    ++PI;
165597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  }
16693f83deba1df95211898fe756758e81969955bd9Owen Anderson
167597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  ++NumCmps;
16893f83deba1df95211898fe756758e81969955bd9Owen Anderson
169597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  if (Result == LazyValueInfo::True)
170597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson    C->replaceAllUsesWith(ConstantInt::getTrue(C->getContext()));
171597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  else
172597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson    C->replaceAllUsesWith(ConstantInt::getFalse(C->getContext()));
17393f83deba1df95211898fe756758e81969955bd9Owen Anderson
174597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  C->eraseFromParent();
175597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson
176597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson  return true;
177597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson}
178597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson
1796f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands/// processSwitch - Simplify a switch instruction by removing cases which can
1806f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands/// never fire.  If the uselessness of a case could be determined locally then
1816f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands/// constant propagation would already have figured it out.  Instead, walk the
1826f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands/// predecessors and statically evaluate cases based on information available
1836f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands/// on that edge.  Cases that cannot fire no matter what the incoming edge can
1846f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands/// safely be removed.  If a case fires on every incoming edge then the entire
1856f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands/// switch can be removed and replaced with a branch to the case destination.
1866f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sandsbool CorrelatedValuePropagation::processSwitch(SwitchInst *SI) {
1876f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  Value *Cond = SI->getCondition();
1886f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  BasicBlock *BB = SI->getParent();
1896f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
1906f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  // If the condition was defined in same block as the switch then LazyValueInfo
1916f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  // currently won't say anything useful about it, though in theory it could.
1926f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  if (isa<Instruction>(Cond) && cast<Instruction>(Cond)->getParent() == BB)
1936f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    return false;
1946f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
1956f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  // If the switch is unreachable then trying to improve it is a waste of time.
1966f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  pred_iterator PB = pred_begin(BB), PE = pred_end(BB);
1976f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  if (PB == PE) return false;
1986f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
1996f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  // Analyse each switch case in turn.  This is done in reverse order so that
2006f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  // removing a case doesn't cause trouble for the iteration.
2016f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  bool Changed = false;
2023d3abe0852d5f499bed7ab014519dd582a0a795dStepan Dyatkovskiy  for (SwitchInst::CaseIt CI = SI->case_end(), CE = SI->case_begin(); CI-- != CE;
2036f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands       ) {
2046f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    ConstantInt *Case = CI.getCaseValue();
2056f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
2066f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    // Check to see if the switch condition is equal to/not equal to the case
2076f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    // value on every incoming edge, equal/not equal being the same each time.
2086f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    LazyValueInfo::Tristate State = LazyValueInfo::Unknown;
2096f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    for (pred_iterator PI = PB; PI != PE; ++PI) {
2106f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // Is the switch condition equal to the case value?
2116f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      LazyValueInfo::Tristate Value = LVI->getPredicateOnEdge(CmpInst::ICMP_EQ,
2126f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands                                                              Cond, Case, *PI, BB);
2136f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // Give up on this case if nothing is known.
2146f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      if (Value == LazyValueInfo::Unknown) {
2156f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands        State = LazyValueInfo::Unknown;
2166f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands        break;
2176f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      }
2186f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
2196f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // If this was the first edge to be visited, record that all other edges
2206f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // need to give the same result.
2216f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      if (PI == PB) {
2226f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands        State = Value;
2236f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands        continue;
2246f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      }
2256f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
2266f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // If this case is known to fire for some edges and known not to fire for
2276f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // others then there is nothing we can do - give up.
2286f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      if (Value != State) {
2296f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands        State = LazyValueInfo::Unknown;
2306f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands        break;
2316f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      }
2326f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    }
2336f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
2346f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    if (State == LazyValueInfo::False) {
2356f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // This case never fires - remove it.
2366f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      CI.getCaseSuccessor()->removePredecessor(BB);
2376f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      SI->removeCase(CI); // Does not invalidate the iterator.
238a8eb6bb408e84ceb468ceb409f4c87308e67b9ebDuncan Sands      ++NumDeadCases;
2396f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      Changed = true;
2406f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    } else if (State == LazyValueInfo::True) {
2416f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // This case always fires.  Arrange for the switch to be turned into an
2426f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // unconditional branch by replacing the switch condition with the case
2436f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      // value.
2446f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      SI->setCondition(Case);
245a8eb6bb408e84ceb468ceb409f4c87308e67b9ebDuncan Sands      NumDeadCases += SI->getNumCases();
2466f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      Changed = true;
2476f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      break;
2486f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    }
2496f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  }
2506f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
2516f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  if (Changed)
2526f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    // If the switch has been simplified to the point where it can be replaced
2536f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    // by a branch then do so now.
2546f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    ConstantFoldTerminator(BB);
2556f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
2566f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands  return Changed;
2576f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands}
2586f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
25925e9405272630204eb721d8b6ab47a5a25f24885Owen Andersonbool CorrelatedValuePropagation::runOnFunction(Function &F) {
260a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson  LVI = &getAnalysis<LazyValueInfo>();
26193f83deba1df95211898fe756758e81969955bd9Owen Anderson
262869a144f4e53db38789e630fbd9cc57384685ce6Owen Anderson  bool FnChanged = false;
26393f83deba1df95211898fe756758e81969955bd9Owen Anderson
2640995f20cfd97110cb842407b5757f217841b0defOwen Anderson  for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
265869a144f4e53db38789e630fbd9cc57384685ce6Owen Anderson    bool BBChanged = false;
266a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ) {
267a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson      Instruction *II = BI++;
2681593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson      switch (II->getOpcode()) {
2691593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson      case Instruction::Select:
2701593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson        BBChanged |= processSelect(cast<SelectInst>(II));
2711593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson        break;
2721593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson      case Instruction::PHI:
2731593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson        BBChanged |= processPHI(cast<PHINode>(II));
2741593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson        break;
275597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson      case Instruction::ICmp:
276597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson      case Instruction::FCmp:
277597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson        BBChanged |= processCmp(cast<CmpInst>(II));
278597dad35b8b86c076dbbb0d095319c79de7806caOwen Anderson        break;
2791593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson      case Instruction::Load:
2801593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson      case Instruction::Store:
2811593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson        BBChanged |= processMemAccess(II);
2821593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson        break;
2831593dd6779d7ab1db13c44f32f987c32aff2b54bOwen Anderson      }
284a0b59f6bd23afaeba923b94f46838cffd5218a12Owen Anderson    }
28593f83deba1df95211898fe756758e81969955bd9Owen Anderson
2866f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    Instruction *Term = FI->getTerminator();
2876f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    switch (Term->getOpcode()) {
2886f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    case Instruction::Switch:
2896f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      BBChanged |= processSwitch(cast<SwitchInst>(Term));
2906f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands      break;
2916f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands    }
2926f1d7994155c535455b7543e2af6dce5b65de37bDuncan Sands
293869a144f4e53db38789e630fbd9cc57384685ce6Owen Anderson    FnChanged |= BBChanged;
2947c37f6d2d9d7fe0327e1de5e0dcda729a73d2a6fOwen Anderson  }
29593f83deba1df95211898fe756758e81969955bd9Owen Anderson
296869a144f4e53db38789e630fbd9cc57384685ce6Owen Anderson  return FnChanged;
2976cfabc7974c74f5a071f9f0621379902614d5179Benjamin Kramer}
298