[Reassociate] Use APInt::isNullValue() instead of comparing with 0. NFC

This should compile to slightly better code.

llvm-svn: 305651
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index a20890b2..4b543b6 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -1136,7 +1136,7 @@
 /// be returned.
 static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd, 
                              const APInt &ConstOpnd) {
-  if (ConstOpnd != 0) {
+  if (!ConstOpnd.isNullValue()) {
     if (!ConstOpnd.isAllOnesValue()) {
       LLVMContext &Ctx = Opnd->getType()->getContext();
       Instruction *I;
@@ -1163,7 +1163,7 @@
   //                       = ((x | c1) ^ c1) ^ (c1 ^ c2)
   //                       = (x & ~c1) ^ (c1 ^ c2)
   // It is useful only when c1 == c2.
-  if (Opnd1->isOrExpr() && Opnd1->getConstPart() != 0) {
+  if (Opnd1->isOrExpr() && !Opnd1->getConstPart().isNullValue()) {
     if (!Opnd1->getValue()->hasOneUse())
       return false;
 
@@ -1221,8 +1221,8 @@
     APInt C3((~C1) ^ C2);
 
     // Do not increase code size!
-    if (C3 != 0 && !C3.isAllOnesValue()) {
-      int NewInstNum = ConstOpnd != 0 ? 1 : 2;
+    if (!C3.isNullValue() && !C3.isAllOnesValue()) {
+      int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
       if (NewInstNum > DeadInstNum)
         return false;
     }
@@ -1238,8 +1238,8 @@
     APInt C3 = C1 ^ C2;
     
     // Do not increase code size
-    if (C3 != 0 && !C3.isAllOnesValue()) {
-      int NewInstNum = ConstOpnd != 0 ? 1 : 2;
+    if (!C3.isNullValue() && !C3.isAllOnesValue()) {
+      int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
       if (NewInstNum > DeadInstNum)
         return false;
     }
@@ -1327,7 +1327,8 @@
     Value *CV;
 
     // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
-    if (ConstOpnd != 0 && CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
+    if (!ConstOpnd.isNullValue() &&
+        CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
       Changed = true;
       if (CV)
         *CurrOpnd = XorOpnd(CV);
@@ -1369,7 +1370,7 @@
       ValueEntry VE(getRank(O.getValue()), O.getValue());
       Ops.push_back(VE);
     }
-    if (ConstOpnd != 0) {
+    if (!ConstOpnd.isNullValue()) {
       Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
       ValueEntry VE(getRank(C), C);
       Ops.push_back(VE);