ValueTracking: Do not look at users of constants for ephemeral values (llvm#134618)

Author: arsenm

llvm/lib/Analysis/ValueTracking.cpp

@@ -446,9 +446,9 @@ void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
 }
 
 static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
-  SmallVector<const Value *, 16> WorkSet(1, I);
-  SmallPtrSet<const Value *, 32> Visited;
-  SmallPtrSet<const Value *, 16> EphValues;
+  SmallVector<const Instruction *, 16> WorkSet(1, I);
+  SmallPtrSet<const Instruction *, 32> Visited;
+  SmallPtrSet<const Instruction *, 16> EphValues;
 
   // The instruction defining an assumption's condition itself is always
   // considered ephemeral to that assumption (even if it has other
@@ -457,23 +457,26 @@ static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
     return true;
 
   while (!WorkSet.empty()) {
-    const Value *V = WorkSet.pop_back_val();
+    const Instruction *V = WorkSet.pop_back_val();
     if (!Visited.insert(V).second)
       continue;
 
     // If all uses of this value are ephemeral, then so is this value.
-    if (llvm::all_of(V->users(), [&](const User *U) {
-                                   return EphValues.count(U);
-                                 })) {
+    if (all_of(V->users(), [&](const User *U) {
+          return EphValues.count(cast<Instruction>(U));
+        })) {
       if (V == E)
         return true;
 
-      if (V == I || (isa<Instruction>(V) &&
-                     !cast<Instruction>(V)->mayHaveSideEffects() &&
-                     !cast<Instruction>(V)->isTerminator())) {
-       EphValues.insert(V);
-       if (const User *U = dyn_cast<User>(V))
-         append_range(WorkSet, U->operands());
+      if (V == I || (!V->mayHaveSideEffects() && !V->isTerminator())) {
+        EphValues.insert(V);
+
+        if (const User *U = dyn_cast<User>(V)) {
+          for (const Use &U : U->operands()) {
+            if (const auto *I = dyn_cast<Instruction>(U.get()))
+              WorkSet.push_back(I);
+          }
+        }
       }
     }
   }