Swift Optimizer: add simplification for tuple_extract

Replace tuple_extract(tuple(x)) -> x

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/CMakeLists.txt

@@ -18,4 +18,5 @@ swift_compiler_sources(Optimizer
   SimplifyGlobalValue.swift
   SimplifyStrongRetainRelease.swift
   SimplifyStructExtract.swift
+  SimplifyTupleExtract.swift
   SimplifyUncheckedEnumData.swift)

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyTupleExtract.swift

@@ -0,0 +1,26 @@
+//===--- SimplifyTupleExtract.swift ---------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SIL
+
+extension TupleExtractInst : OnoneSimplifyable {
+  func simplify(_ context: SimplifyContext) {
+
+    // Replace tuple_extract(tuple(x)) -> x
+
+    guard let tupleInst = tuple as? TupleInst else {
+      return
+    }
+    context.tryReplaceRedundantInstructionPair(first: tupleInst, second: self,
+                                               with: tupleInst.operands[fieldIndex].value)
+  }
+}

test/SILOptimizer/simplify_tuple_extract.sil

@@ -0,0 +1,39 @@
+// RUN: %target-sil-opt -enable-sil-verify-all %s -onone-simplification -simplify-instruction=tuple_extract | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+
+import Swift
+import Builtin
+
+// CHECK-LABEL: sil @tuple_extract_first_field
+// CHECK:         return %0
+// CHECK:       } // end sil function 'tuple_extract_first_field'
+sil @tuple_extract_first_field : $@convention(thin) (@owned String, @guaranteed String) -> @owned String {
+bb0(%0 : $String, %1 : $String):
+  %2 = tuple (%0 : $String, %1 : $String)
+  %3 = tuple_extract %2 : $(String, String), 0
+  return %3 : $String
+}
+
+// CHECK-LABEL: sil @tuple_extract_second_field
+// CHECK:         return %1
+// CHECK:       } // end sil function 'tuple_extract_second_field'
+sil @tuple_extract_second_field : $@convention(thin) (@guaranteed String, @owned String) -> @owned String {
+bb0(%0 : $String, %1 : $String):
+  %2 = tuple (%0 : $String, %1 : $String)
+  %3 = tuple_extract %2 : $(String, String), 1
+  return %3 : $String
+}
+
+// CHECK-LABEL: sil [ossa] @tuple_extract_ossa
+// CHECK:         %2 = copy_value %0
+// CHECK:         return %2
+// CHECK:       } // end sil function 'tuple_extract_ossa'
+sil [ossa] @tuple_extract_ossa : $@convention(thin) (@guaranteed String, @guaranteed String) -> @owned String {
+bb0(%0 : @guaranteed $String, %1 : @guaranteed $String):
+  %2 = tuple (%0 : $String, %1 : $String)
+  %3 = tuple_extract %2 : $(String, String), 0
+  %4 = copy_value %3 : $String
+  return %4 : $String
+}
+