[sil-opaque-values] Teach the SIL cloner to skip trivial copy/destroy.

This reduces the amount of SIL generated by 14x.

Author: atrick

include/swift/SIL/TypeSubstCloner.h

@@ -262,6 +262,25 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
     super::visitUpcastInst(Upcast);
   }
 
+  void visitCopyValueInst(CopyValueInst *Copy) {
+    // If the substituted type is trivial, ignore the copy.
+    SILType copyTy = getOpType(Copy->getType());
+    if (copyTy.isTrivial(Copy->getModule())) {
+      ValueMap.insert({SILValue(Copy), getOpValue(Copy->getOperand())});
+      return;
+    }
+    super::visitCopyValueInst(Copy);
+  }
+
+  void visitDestroyValueInst(DestroyValueInst *Destroy) {
+    // If the substituted type is trivial, ignore the destroy.
+    SILType destroyTy = getOpType(Destroy->getOperand()->getType());
+    if (destroyTy.isTrivial(Destroy->getModule())) {
+      return;
+    }
+    super::visitDestroyValueInst(Destroy);
+  }
+
   /// The Swift module that the cloned function belongs to.
   ModuleDecl *SwiftMod;
   /// The substitutions list for the specialization.

test/SILOptimizer/specialize_opaque.sil

@@ -0,0 +1,35 @@
+// RUN: %target-sil-opt -enable-sil-opaque-values -assume-parsing-unqualified-ownership-sil -enable-sil-verify-all -generic-specializer %s | %FileCheck %s
+
+sil_stage canonical
+
+import Builtin
+
+// Test that foo is specialized on Builtin.Int64 and the copy_values and destroy_values are dropped.
+//
+// CHECK-LABEL: sil shared @_T03fooBi64__Tg5 : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> () {
+// CHECK: bb0(%0 : $Builtin.Int64, %1 : $Builtin.Int64):
+// CHECK:   [[F:%.*]] = function_ref @_T03fooBi64__Tg5 : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> ()
+// CHECK:   %{{.*}} = apply [[F]](%0, %1) : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> ()
+// CHECK-NOT: copy_value
+// CHECK-NOT: destroy_value
+// CHECK:   return %{{.*}} : $()
+// CHECK-LABEL: } // end sil function '_T03fooBi64__Tg5'
+sil hidden @foo : $@convention(thin) <T> (@in T, @in T) -> () {
+bb0(%0 : $T, %1 : $T):
+  %f = function_ref @foo : $@convention(thin) <τ_0_0> (@in τ_0_0, @in τ_0_0) -> ()
+  %cp0 = copy_value %0 : $T
+  %cp1 = copy_value %1 : $T
+  %call = apply %f<T>(%cp0, %cp1) : $@convention(thin) <τ_0_0> (@in τ_0_0, @in τ_0_0) -> ()
+  destroy_value %1 : $T
+  destroy_value %0 : $T
+  %10 = tuple ()
+  return %10 : $()
+}
+
+sil @testSpecialize : $@convention(thin) (Builtin.Int64) -> () {
+bb0(%0: $Builtin.Int64):
+  %f = function_ref @foo : $@convention(thin) <T> (@in T, @in T) -> ()
+  %call = apply %f<Builtin.Int64>(%0, %0) : $@convention(thin) <τ_0_0> (@in τ_0_0, @in τ_0_0) -> ()
+  %999 = tuple ()
+  return %999 : $()
+}