InstructionDeleter - delete dead alloc_stack

Author: atrick

lib/SILOptimizer/Utils/InstOptUtils.cpp

@@ -216,9 +216,11 @@ bool swift::hasOnlyEndOfScopeOrEndOfLifetimeUses(SILInstruction *inst) {
     for (Operand *use : result->getUses()) {
       SILInstruction *user = use->getUser();
       bool isDebugUser = user->isDebugInstruction();
-      if (!isa<DestroyValueInst>(user) && !isa<EndLifetimeInst>(user) &&
-          !isEndOfScopeMarker(user) && !isDebugUser)
+      if (!isa<DestroyValueInst>(user) && !isa<EndLifetimeInst>(user)
+          && !isa<DeallocStackInst>(user) && !isEndOfScopeMarker(user)
+          && !isDebugUser) {
         return false;
+      }
       // Include debug uses only in Onone mode.
       if (isDebugUser && inst->getFunction()->getEffectiveOptimizationMode() <=
                              OptimizationMode::NoOptimization)

lib/SILOptimizer/Utils/InstructionDeleter.cpp

@@ -66,6 +66,12 @@ static bool isScopeAffectingInstructionDead(SILInstruction *inst,
     return true;
 
   switch (inst->getKind()) {
+  case SILInstructionKind::AllocStackInst: {
+    // An alloc_stack only used by dealloc_stack is dead.
+    return
+      fun->getEffectiveOptimizationMode() > OptimizationMode::NoOptimization
+      || !cast<AllocStackInst>(inst)->getVarInfo();
+  }
   case SILInstructionKind::LoadBorrowInst: {
     // A load_borrow only used in an end_borrow is dead.
     return true;
@@ -205,8 +211,8 @@ void InstructionDeleter::deleteWithUses(SILInstruction *inst, bool fixLifetimes,
       auto uses = llvm::to_vector<4>(result->getUses());
       for (Operand *use : uses) {
         SILInstruction *user = use->getUser();
-        assert(forceDeleteUsers || isIncidentalUse(user) ||
-               isa<DestroyValueInst>(user));
+        assert(forceDeleteUsers || isIncidentalUse(user)
+               || isa<DestroyValueInst>(user) || isa<DeallocStackInst>(user));
         assert(!isa<BranchInst>(user) && "can't delete phis");
 
         toDeleteInsts.push_back(user);