[InstSimplify] move select undef cond fold with other constant cond folds; NFCI

llvm-svn: 325434

1 files changed, 21 insertions, 20 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index e81d7672b88..34a10c5d5ea 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3681,37 +3681,38 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal,
 
 /// Given operands for a SelectInst, see if we can fold the result.
 /// If not, this returns null.
-static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
-                                 Value *FalseVal, const SimplifyQuery &Q,
-                                 unsigned MaxRecurse) {
-  // select true, X, Y  -> X
-  // select false, X, Y -> Y
-  if (Constant *CB = dyn_cast<Constant>(CondVal)) {
-    if (Constant *CT = dyn_cast<Constant>(TrueVal))
-      if (Constant *CF = dyn_cast<Constant>(FalseVal))
-        return ConstantFoldSelectInstruction(CB, CT, CF);
-    if (CB->isAllOnesValue())
+static Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
+                                 const SimplifyQuery &Q, unsigned MaxRecurse) {
+  if (auto *CondC = dyn_cast<Constant>(Cond)) {
+    if (auto *TrueC = dyn_cast<Constant>(TrueVal))
+      if (auto *FalseC = dyn_cast<Constant>(FalseVal))
+        return ConstantFoldSelectInstruction(CondC, TrueC, FalseC);
+
+    // select undef, X, Y -> X or Y
+    if (isa<UndefValue>(CondC))
+      return isa<Constant>(FalseVal) ? FalseVal : TrueVal;
+
+    // TODO: Vector constants with undef elements don't simplify.
+
+    // select true, X, Y  -> X
+    if (CondC->isAllOnesValue())
       return TrueVal;
-    if (CB->isNullValue())
+    // select false, X, Y -> Y
+    if (CondC->isNullValue())
       return FalseVal;
   }
 
-  // select C, X, X -> X
+  // select ?, X, X -> X
   if (TrueVal == FalseVal)
     return TrueVal;
 
-  if (isa<UndefValue>(CondVal)) {  // select undef, X, Y -> X or Y
-    if (isa<Constant>(FalseVal))
-      return FalseVal;
-    return TrueVal;
-  }
-  if (isa<UndefValue>(TrueVal))   // select C, undef, X -> X
+  if (isa<UndefValue>(TrueVal))   // select ?, undef, X -> X
     return FalseVal;
-  if (isa<UndefValue>(FalseVal))   // select C, X, undef -> X
+  if (isa<UndefValue>(FalseVal))   // select ?, X, undef -> X
     return TrueVal;
 
   if (Value *V =
-          simplifySelectWithICmpCond(CondVal, TrueVal, FalseVal, Q, MaxRecurse))
+          simplifySelectWithICmpCond(Cond, TrueVal, FalseVal, Q, MaxRecurse))
     return V;
 
   return nullptr;