[ownership] When splitting destructures, simplify the instruction if possible.

I noticed that this is needed at -Onone to maintain the same codegen output.

Author: gottesmm

lib/SILOptimizer/Transforms/OwnershipModelEliminator.cpp

@@ -275,10 +275,19 @@ static void splitDestructure(SILBuilder &B, SILInstruction *I, SILValue Op) {
     SingleValueInstruction *ProjInst =
         Proj.createObjectProjection(B, Loc, Op).get();
 
+    // If we can simplify, do so.
+    if (SILValue NewV = simplifyInstruction(ProjInst)) {
+      Result->replaceAllUsesWith(NewV);
+      ProjInst->eraseFromParent();
+      continue;
+    }
+
     Result->replaceAllUsesWith(ProjInst);
   }
 
-  I->eraseFromParent();
+  // We may have exposed trivially dead instructions due to
+  // simplifyInstruction... delete I and any such instructions!
+  recursivelyDeleteTriviallyDeadInstructions(I, true);
 }
 
 bool OwnershipModelEliminatorVisitor::visitDestructureStructInst(

test/SILOptimizer/ownership_model_eliminator.sil

@@ -318,3 +318,14 @@ bb0(%0 : @owned $(Builtin.NativeObject, Builtin.Int32), %1 : @owned $TestArray2)
   %7 = tuple (%2 : $Builtin.NativeObject, %4 : $TestArrayStorage, %6 : $TestArrayStorage)
   return %7 : $(Builtin.NativeObject, TestArrayStorage, TestArrayStorage)
 }
+
+// CHECK-LABEL: sil [canonical] @test_simplify_instruction : $@convention(thin) (@owned Builtin.NativeObject, Builtin.Int32) -> @owned Builtin.NativeObject {
+// CHECK: bb0([[ARG:%.*]] : $Builtin.NativeObject,
+// CHECK-NEXT:   return [[ARG]]
+// CHECK: } // end sil function 'test_simplify_instruction'
+sil [canonical] [ossa] @test_simplify_instruction : $@convention(thin) (@owned Builtin.NativeObject, Builtin.Int32) -> @owned Builtin.NativeObject {
+bb0(%0 : @owned $Builtin.NativeObject, %1 : $Builtin.Int32):
+  %2 = tuple(%0 : $Builtin.NativeObject, %1 : $Builtin.Int32)
+  (%3, %4) = destructure_tuple %2 : $(Builtin.NativeObject, Builtin.Int32)
+  return %3 : $Builtin.NativeObject
+}

test/Serialization/transparent-std.swift

@@ -16,13 +16,17 @@ func test_foo(x: Builtin.Int1, y: Builtin.Int1) -> Builtin.Int1 {
 }
 
 // SIL-LABEL: sil public_external [transparent] [serialized] [canonical] @$s19def_transparent_std12assign_tuple1x1yyBi64__Bot_BptF : $@convention(thin) (Builtin.Int64, @guaranteed Builtin.NativeObject, Builtin.RawPointer) -> () {
-// SIL: = tuple (%0 : $Builtin.Int64, %1 : $Builtin.NativeObject)
-// SIL: retain_value
-// SIL: = tuple_extract
-// SIL: = tuple_extract
-// SIL: = pointer_to_address
-// SIL: = tuple
-// SIL: = load
+// SIL: bb0([[ARG0:%.*]] : ${{.*}}, [[ARG1:%.*]] : ${{.*}}, [[ARG2:%.*]] :
+// SIL: [[TUP:%.*]] = tuple ([[ARG0]] : $Builtin.Int64, [[ARG1]] : $Builtin.NativeObject)
+// SIL: retain_value [[TUP]]
+// SIL: [[CASTED_PTR:%.*]] = pointer_to_address [[ARG2]]
+// SIL: [[CASTED_PTR_0:%.*]] = tuple_element_addr [[CASTED_PTR]] : $*(Builtin.Int64, Builtin.NativeObject), 0
+// SIL: store [[ARG0]] to [[CASTED_PTR_0]]
+// SIL: [[CASTED_PTR_1:%.*]] = tuple_element_addr [[CASTED_PTR]] : $*(Builtin.Int64, Builtin.NativeObject), 1
+// SIL: [[OLD_VALUE:%.*]] = load [[CASTED_PTR_1]]
+// SIL: store [[ARG1]] to [[CASTED_PTR_1]]
+// SIL: strong_release [[OLD_VALUE]]
+// SIL: } // end sil function '$s19def_transparent_std12assign_tuple1x1yyBi64__Bot_BptF' 
 func test_tuple(x: (Builtin.Int64, Builtin.NativeObject),
                 y: Builtin.RawPointer) {
   assign_tuple(x: x, y: y)