X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FInstructionCombining.cpp;h=92b7f1a39bc719a7c367ff8fadc1463d8f10dc2e;hb=6ffe551f657c948d6a473a198ecbd1188bf9ce45;hp=23d0f5ffcc78f78f4f9b6431cbadd085fc2a9dd1;hpb=66331a4e3312af6cc07b8c583565cc53d5b1516a;p=oota-llvm.git

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 23d0f5ffcc7..92b7f1a39bc 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -397,30 +397,6 @@ Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
     // reassociate the expression from ((? op A) op B) to (? op (A op B))
     if (ShouldApply) {
       BasicBlock *BB = Root.getParent();
-      // All of the instructions have a single use and have no side-effects,
-      // because of this, we can pull them all into the current basic block.
-      if (LHSI->getParent() != BB) {
-        // Move all of the instructions from root to LHSI into the current
-        // block.
-        Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
-        Instruction *LastUse = &Root;
-        while (TmpLHSI->getParent() == BB) {
-          LastUse = TmpLHSI;
-          TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
-        }
-        
-        // Loop over all of the instructions in other blocks, moving them into
-        // the current one.
-        Value *TmpLHS = TmpLHSI;
-        do {
-          TmpLHSI = cast<Instruction>(TmpLHS);
-          // Remove from current block...
-          TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
-          // Insert before the last instruction...
-          BB->getInstList().insert(LastUse, TmpLHSI);
-          TmpLHS = TmpLHSI->getOperand(0);
-        } while (TmpLHSI != LHSI);
-      }
       
       // Now all of the instructions are in the current basic block, go ahead
       // and perform the reassociation.
@@ -431,20 +407,27 @@ Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
 
       // Make what used to be the LHS of the root be the user of the root...
       Value *ExtraOperand = TmpLHSI->getOperand(1);
-      if (&Root != TmpLHSI)
-        Root.replaceAllUsesWith(TmpLHSI);        // Users now use TmpLHSI
-      else {
+      if (&Root == TmpLHSI) {
         Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
         return 0;
       }
+      Root.replaceAllUsesWith(TmpLHSI);          // Users now use TmpLHSI
       TmpLHSI->setOperand(1, &Root);             // TmpLHSI now uses the root
-      BB->getInstList().remove(&Root);           // Remove root from the BB
-      BB->getInstList().insert(TmpLHSI, &Root);  // Insert root before TmpLHSI
+      TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
+      BasicBlock::iterator ARI = &Root; ++ARI;
+      BB->getInstList().insert(ARI, TmpLHSI);    // Move TmpLHSI to after Root
+      ARI = Root;
 
       // Now propagate the ExtraOperand down the chain of instructions until we
       // get to LHSI.
       while (TmpLHSI != LHSI) {
         Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
+        // Move the instruction to immediately before the chain we are
+        // constructing to avoid breaking dominance properties.
+        NextLHSI->getParent()->getInstList().remove(NextLHSI);
+        BB->getInstList().insert(ARI, NextLHSI);
+        ARI = NextLHSI;
+
         Value *NextOp = NextLHSI->getOperand(1);
         NextLHSI->setOperand(1, ExtraOperand);
         TmpLHSI = NextLHSI;
@@ -866,11 +849,15 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
 }
 
 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
-  // div X, 1 == X
   if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
+    // div X, 1 == X
     if (RHS->equalsInt(1))
       return ReplaceInstUsesWith(I, I.getOperand(0));
 
+    // div X, -1 == -X
+    if (RHS->isAllOnesValue())
+      return BinaryOperator::createNeg(I.getOperand(0));
+
     // Check to see if this is an unsigned division with an exact power of 2,
     // if so, convert to a right shift.
     if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
@@ -2209,6 +2196,28 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
         return new CastInst(NotCond, SI.getType());
       }
     }
+
+  // See if we are selecting two values based on a comparison of the two values.
+  if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
+    if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
+      // Transform (X == Y) ? X : Y  -> Y
+      if (SCI->getOpcode() == Instruction::SetEQ)
+        return ReplaceInstUsesWith(SI, FalseVal);
+      // Transform (X != Y) ? X : Y  -> X
+      if (SCI->getOpcode() == Instruction::SetNE)
+        return ReplaceInstUsesWith(SI, TrueVal);
+      // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
+
+    } else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
+      // Transform (X == Y) ? Y : X  -> X
+      if (SCI->getOpcode() == Instruction::SetEQ)
+        return ReplaceInstUsesWith(SI, FalseVal);
+      // Transform (X != Y) ? Y : X  -> Y
+      if (SCI->getOpcode() == Instruction::SetNE)
+        return ReplaceInstUsesWith(SI, TrueVal);
+      // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
+    }
+  }
   
   // See if we can fold the select into one of our operands.
   if (SI.getType()->isInteger()) {
@@ -2575,7 +2584,10 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
       // obvious.
       Value *Op = GEP.getOperand(i);
       if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
-        if (!isa<Constant>(Op)) {
+        if (Constant *C = dyn_cast<Constant>(Op)) {
+          GEP.setOperand(i, ConstantExpr::getCast(C, TD->getIntPtrType()));
+          MadeChange = true;
+        } else {
           Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
                                                 Op->getName()), GEP);
           GEP.setOperand(i, Op);
@@ -2831,8 +2843,11 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
   Value *Op = LI.getOperand(0);
   if (LI.isVolatile()) return 0;
 
-  if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
-    Op = CPR->getValue();
+  if (Constant *C = dyn_cast<Constant>(Op))
+    if (C->isNullValue())  // load null -> 0
+      return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
+    else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C))
+      Op = CPR->getValue();
 
   // Instcombine load (constant global) into the value loaded...
   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
@@ -2919,7 +2934,10 @@ bool InstCombiner::runOnFunction(Function &F) {
   bool Changed = false;
   TD = &getAnalysis<TargetData>();
 
-  WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
+  for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i) {
+      WorkList.push_back(&*i);
+  }
+
 
   while (!WorkList.empty()) {
     Instruction *I = WorkList.back();  // Get an instruction from the worklist