Fixes and cleanups pointed out by Chris. In general, be careful to handle 0 results from ComputeValueKnownInPredecessors

(indicating undef), and re-use existing constant folding APIs.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112539 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 16 deletions

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index c0b0cbebde..2955ca1ab5 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -16,6 +16,7 @@
 #include "llvm/IntrinsicInst.h"
 #include "llvm/LLVMContext.h"
 #include "llvm/Pass.h"
+#include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/LazyValueInfo.h"
 #include "llvm/Analysis/Loads.h"
@@ -86,6 +87,7 @@ namespace {
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       if (EnableLVI)
         AU.addRequired<LazyValueInfo>();
+      AU.addPreserved<LazyValueInfo>();
     }
     
     void FindLoopHeaders(Function &F);
@@ -325,9 +327,10 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
       } else if (LVI) {
         Constant *CI = LVI->getConstantOnEdge(InVal,
                                               PN->getIncomingBlock(i), BB);
-        ConstantInt *CInt = dyn_cast_or_null<ConstantInt>(CI);
-        if (CInt)
-          Result.push_back(std::make_pair(CInt, PN->getIncomingBlock(i)));
+        // LVI returns null is no value could be determined.
+        if (!CI) continue;
+        ConstantInt *CInt = dyn_cast<ConstantInt>(CI);
+        Result.push_back(std::make_pair(CInt, PN->getIncomingBlock(i)));
       }
     }
     return !Result.empty();
@@ -373,10 +376,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
           }
         }
       return !Result.empty();
-    
-    // Try to process a few other binary operator patterns.
-    } else if (isa<BinaryOperator>(I)) {
-      
     }
     
     // Handle the NOT form of XOR.
@@ -400,12 +399,14 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
     // AND or OR of a value with itself is that value.
     ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1));
     if (CI && (BO->getOpcode() == Instruction::And ||
-         BO->getOpcode() == Instruction::Or)) {
+        BO->getOpcode() == Instruction::Or)) {
       SmallVector<std::pair<ConstantInt*, BasicBlock*>, 8> LHSVals;
       ComputeValueKnownInPredecessors(BO->getOperand(0), BB, LHSVals);
-      for (unsigned i = 0, e = LHSVals.size(); i != e; ++i) 
-        if (LHSVals[i].first == CI)
-        Result.push_back(std::make_pair(CI, LHSVals[i].second));
+      for (unsigned i = 0, e = LHSVals.size(); i != e; ++i)
+        if (LHSVals[i].first == 0)
+          Result.push_back(std::make_pair((ConstantInt*)0, LHSVals[i].second));
+        else if (LHSVals[i].first == CI)
+          Result.push_back(std::make_pair(CI, LHSVals[i].second));
       
       return !Result.empty();
     }
@@ -450,7 +451,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
     if (LVI && isa<Constant>(Cmp->getOperand(1)) &&
         Cmp->getType()->isIntegerTy()) {
       if (!isa<Instruction>(Cmp->getOperand(0)) ||
-           cast<Instruction>(Cmp->getOperand(0))->getParent() != BB) {
+          cast<Instruction>(Cmp->getOperand(0))->getParent() != BB) {
         Constant *RHSCst = cast<Constant>(Cmp->getOperand(1));
 
         for (pred_iterator PI = pred_begin(BB), E = pred_end(BB);PI != E; ++PI){
@@ -472,17 +473,20 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
       
       // Try to find a constant value for the LHS of an equality comparison,
       // and evaluate it statically if we can.
-      if (Cmp->getPredicate() == CmpInst::ICMP_EQ || 
-          Cmp->getPredicate() == CmpInst::ICMP_NE) {
+      if (Constant *CmpConst = dyn_cast<Constant>(Cmp->getOperand(1))) {
         SmallVector<std::pair<ConstantInt*, BasicBlock*>, 8> LHSVals;
         ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals);
         
         ConstantInt *True = ConstantInt::getTrue(I->getContext());
         ConstantInt *False = ConstantInt::getFalse(I->getContext());
-        if (Cmp->getPredicate() == CmpInst::ICMP_NE) std::swap(True, False);
         
         for (unsigned i = 0, e = LHSVals.size(); i != e; ++i) {
-          if (LHSVals[i].first == Cmp->getOperand(1))
+          if (LHSVals[i].first == 0)
+            Result.push_back(std::make_pair((ConstantInt*)0,
+                                            LHSVals[i].second));
+          else if (ConstantFoldCompareInstOperands(Cmp->getPredicate(), 
+                                              LHSVals[i].first, 
+                                              CmpConst))
             Result.push_back(std::make_pair(True, LHSVals[i].second));
           else 
             Result.push_back(std::make_pair(False, LHSVals[i].second));