[AddressLowering] Rewrite newly created uses.

When rewriting uses, it is possible for new uses of a value to be
created, as when a  debug_value instruction is created when a store
instruction is deleted.  Ensure that all uses are rewritten by adding
all uses to the worklist of uses after rewriting each use.

Author: nate-chandler

lib/SILOptimizer/Mandatory/AddressLowering.cpp

@@ -3362,8 +3362,19 @@ static void rewriteFunction(AddressLoweringState &pass) {
     if (valueDef->getType().isAddress())
       continue;
 
+    SmallPtrSet<Operand *, 8> originalUses;
     SmallVector<Operand *, 8> uses(valueDef->getUses());
-    for (Operand *oper : uses) {
+    for (auto *oper : uses) {
+      originalUses.insert(oper);
+      UseRewriter::rewriteUse(oper, pass);
+    }
+    uses.clear();
+    for (auto *use : valueDef->getUses()) {
+      uses.push_back(use);
+    }
+    for (auto *oper : uses) {
+      if (originalUses.contains(oper))
+        continue;
       UseRewriter::rewriteUse(oper, pass);
     }
   }

test/SILOptimizer/address_lowering_phi.sil

@@ -470,3 +470,33 @@ bb2:
 bb3(%phi : @owned $T):
   return %phi : $T
 }
+
+// Check that the debug_value instruction that is created when deleting a load
+// gets rewritten and doesn't obstruct the deletion of the phi.
+// CHECK-LABEL: sil [ossa] @f100_store_phi : {{.*}} {
+// CHECK:       {{bb[0-9]+}}({{%[^,]+}} : $*Value):
+// CHECK:         [[TEMP:%[^,]+]] = alloc_stack $Value
+// CHECK:         [[VAR:%[^,]+]] = alloc_stack [lexical] $Value, var, name "value"
+// CHECK:         cond_br undef, bb2, bb1
+// CHECK:       bb3:
+// CHECK:         copy_addr [take] [[TEMP]] to [init] [[VAR]]
+// CHECK:         debug_value [[TEMP]] : $*Value, var, name "value"
+// CHECK-LABEL: } // end sil function 'f100_store_phi'
+sil [ossa] @f100_store_phi : $@convention(thin) <Value> (@in Value) -> () {
+entry(%instance : @owned $Value):
+  %14 = alloc_stack [lexical] $Value, var, name "value"
+  cond_br undef, left, right
+
+left:
+  br merge(%instance : $Value)
+
+right:
+  br merge(%instance : $Value)
+
+merge(%34 : @owned $Value):
+  store %34 to [init] %14 : $*Value
+  destroy_addr %14 : $*Value
+  dealloc_stack %14 : $*Value
+  %43 = tuple ()
+  return %43 : $()
+}