[InstCombine] fix formatting in SimplifyDemandedVectorElts->Select; NFCI

rotateright · rotateright · commit 1a00ffd65636 · 2018-09-06T13:19:22.000Z
I'm preparing to add the same functionality both here and to the DAG 
version of this code in D51696 / D51433, so try to make those cases 
as similar as possible to avoid bugs.

llvm-svn: 341545
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -1260,8 +1260,8 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
     break;
   }
   case Instruction::Select: {
-    APInt LeftDemanded(DemandedElts), RightDemanded(DemandedElts);
-    if (ConstantVector* CV = dyn_cast<ConstantVector>(I->getOperand(0))) {
+    APInt DemandedLHS(DemandedElts), DemandedRHS(DemandedElts);
+    if (auto *CV = dyn_cast<ConstantVector>(I->getOperand(0))) {
       for (unsigned i = 0; i < VWidth; i++) {
         Constant *CElt = CV->getAggregateElement(i);
         // Method isNullValue always returns false when called on a
@@ -1270,22 +1270,26 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
         if (isa<ConstantExpr>(CElt))
           continue;
         if (CElt->isNullValue())
-          LeftDemanded.clearBit(i);
+          DemandedLHS.clearBit(i);
         else
-          RightDemanded.clearBit(i);
+          DemandedRHS.clearBit(i);
       }
     }
 
-    TmpV = SimplifyDemandedVectorElts(I->getOperand(1), LeftDemanded, UndefElts,
-                                      Depth + 1);
-    if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
+    if (Value *V = SimplifyDemandedVectorElts(I->getOperand(1), DemandedLHS,
+                                              UndefElts2, Depth + 1)) {
+      I->setOperand(1, V);
+      MadeChange = true;
+    }
 
-    TmpV = SimplifyDemandedVectorElts(I->getOperand(2), RightDemanded,
-                                      UndefElts2, Depth + 1);
-    if (TmpV) { I->setOperand(2, TmpV); MadeChange = true; }
+    if (Value *V = SimplifyDemandedVectorElts(I->getOperand(2), DemandedRHS,
+                                              UndefElts3, Depth + 1)) {
+      I->setOperand(2, V);
+      MadeChange = true;
+    }
 
-    // Output elements are undefined if both are undefined.
-    UndefElts &= UndefElts2;
+    // Output elements are undefined if the element from each arm is undefined.
+    UndefElts = UndefElts2 & UndefElts3;
     break;
   }
   case Instruction::BitCast: {
