[NFC] Move findAllocaForValue into ValueTracking.h

Differential Revision: https://reviews.llvm.org/D84616

1 files changed, 35 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 3b8c0fc..6fb36fa 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4313,6 +4313,41 @@ bool llvm::getUnderlyingObjectsForCodeGen(const Value *V,
   return true;
 }
 
+AllocaInst *
+llvm::findAllocaForValue(Value *V,
+                         DenseMap<Value *, AllocaInst *> &AllocaForValue) {
+  if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
+    return AI;
+  // See if we've already calculated (or started to calculate) alloca for a
+  // given value.
+  auto I = AllocaForValue.find(V);
+  if (I != AllocaForValue.end())
+    return I->second;
+  // Store 0 while we're calculating alloca for value V to avoid
+  // infinite recursion if the value references itself.
+  AllocaForValue[V] = nullptr;
+  AllocaInst *Res = nullptr;
+  if (CastInst *CI = dyn_cast<CastInst>(V))
+    Res = findAllocaForValue(CI->getOperand(0), AllocaForValue);
+  else if (PHINode *PN = dyn_cast<PHINode>(V)) {
+    for (Value *IncValue : PN->incoming_values()) {
+      // Allow self-referencing phi-nodes.
+      if (IncValue == PN)
+        continue;
+      AllocaInst *IncValueAI = findAllocaForValue(IncValue, AllocaForValue);
+      // AI for incoming values should exist and should all be equal.
+      if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res))
+        return nullptr;
+      Res = IncValueAI;
+    }
+  } else if (GetElementPtrInst *EP = dyn_cast<GetElementPtrInst>(V)) {
+    Res = findAllocaForValue(EP->getPointerOperand(), AllocaForValue);
+  }
+  if (Res)
+    AllocaForValue[V] = Res;
+  return Res;
+}
+
 static bool onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
     const Value *V, bool AllowLifetime, bool AllowDroppable) {
   for (const User *U : V->users()) {