SimplifyDestructure: convert destructure_tuple/destructure_struct with guaranteed ownership to to tuple_extract/struct_extract

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyDestructure.swift

@@ -50,19 +50,6 @@ private extension DestructureInstruction {
 
   func foldWithAggregateConstruction(_ context: SimplifyContext) {
 
-    if aggregate.type.isTrivial(in: parentFunction) {
-      // ```
-      //   (%1, %2) = destructure_tuple %t
-      // ```
-      // ->
-      // ```
-      //   %1 = tuple_extract %t, 0
-      //   %2 = tuple_extract %t, 1
-      // ```
-      replaceWithAggregateExtract(context)
-      return
-    }
-
     switch aggregate {
     case let constructInst as ConstructureInstruction:
       // Eliminate the redundant instruction pair
@@ -99,6 +86,21 @@ private extension DestructureInstruction {
     default:
       break
     }
+
+    if !isDeleted,
+       aggregate.type.isTrivial(in: parentFunction) || aggregate.ownership == .guaranteed
+    {
+      // ```
+      //   (%1, %2) = destructure_tuple %t
+      // ```
+      // ->
+      // ```
+      //   %1 = tuple_extract %t, 0
+      //   %2 = tuple_extract %t, 1
+      // ```
+      replaceWithAggregateExtract(context)
+      return
+    }
   }
 
   private func replaceWithAggregateExtract(_ context: SimplifyContext) {

test/SILOptimizer/sil_combine_misc_opts.sil

@@ -102,7 +102,7 @@ bb0(%0 : $*Builtin.NativeObject):
 }
 
 // CHECK-LABEL: sil [ossa] @test_updating_borrowed_from :
-// CHECK:         borrowed {{.*}} from (%0 : $S)
+// this is not optimized anymore in SILCombine
 // CHECK-LABEL: } // end sil function 'test_updating_borrowed_from'
 sil [ossa] @test_updating_borrowed_from : $@convention(thin) (@guaranteed S) -> () {
 bb0(%0 : @guaranteed $S):

test/SILOptimizer/simplify_destructure_struct.sil

@@ -158,3 +158,16 @@ bb0(%0 : $TrivialS):
   return %3
 }
 
+// CHECK-LABEL: sil [ossa] @guaranteed_to_struct_extract :
+// CHECK:         %1 = struct_extract %0 : $S, #S.a
+// CHECK:         %2 = struct_extract %0 : $S, #S.b
+// CHECK:       } // end sil function 'guaranteed_to_struct_extract'
+sil [ossa] @guaranteed_to_struct_extract : $@convention(thin) (@guaranteed S) -> () {
+bb0(%0 : @guaranteed $S):
+  (%1, %2) = destructure_struct %0
+  fix_lifetime %1
+  fix_lifetime %2
+  %r = tuple ()
+  return %r
+}
+

test/SILOptimizer/simplify_destructure_tuple.sil

@@ -153,3 +153,16 @@ bb0(%0 : $(Int, Int)):
   return %3
 }
 
+// CHECK-LABEL: sil [ossa] @guaranteed_to_tuple_extract :
+// CHECK:         %1 = tuple_extract %0 : $(String, Int), 0
+// CHECK:         %2 = tuple_extract %0 : $(String, Int), 1
+// CHECK:       } // end sil function 'guaranteed_to_tuple_extract'
+sil [ossa] @guaranteed_to_tuple_extract : $@convention(thin) (@guaranteed (String, Int)) -> () {
+bb0(%0 : @guaranteed $(String, Int)):
+  (%1, %2) = destructure_tuple %0
+  fix_lifetime %1
+  fix_lifetime %2
+  %r = tuple ()
+  return %r
+}
+