Swift Optimizer: add Onone simplification of struct_extract instructions

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/CMakeLists.txt

@@ -14,4 +14,5 @@ swift_compiler_sources(Optimizer
   SimplifyCondBranch.swift
   SimplifyGlobalValue.swift
   SimplifyStrongRetainRelease.swift
+  SimplifyStructExtract.swift
   SimplifyUncheckedEnumData.swift)

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyStructExtract.swift

@@ -0,0 +1,23 @@
+//===--- SimplifyStructExtract.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 StructExtractInst : OnoneSimplifyable {
+  func simplify(_ context: SimplifyContext) {
+    guard let structInst = operand as? StructInst else {
+      return
+    }
+    context.tryReplaceRedundantInstructionPair(first: structInst, second: self,
+                                               with: structInst.operands[fieldIndex].value)
+  }
+}

test/SILOptimizer/simplify_struct_extract.sil

@@ -0,0 +1,44 @@
+// RUN: %target-sil-opt -enable-sil-verify-all %s -onone-simplification -simplify-instruction=struct_extract | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+
+import Swift
+import Builtin
+
+struct S {
+  var a: String
+  var b: String
+}
+
+// CHECK-LABEL: sil @struct_extract_first_field
+// CHECK:         return %0
+// CHECK:       } // end sil function 'struct_extract_first_field'
+sil @struct_extract_first_field : $@convention(thin) (@owned String, @guaranteed String) -> @owned String {
+bb0(%0 : $String, %1 : $String):
+  %2 = struct $S (%0 : $String, %1 : $String)
+  %3 = struct_extract %2 : $S, #S.a
+  return %3 : $String
+}
+
+// CHECK-LABEL: sil @struct_extract_second_field
+// CHECK:         return %1
+// CHECK:       } // end sil function 'struct_extract_second_field'
+sil @struct_extract_second_field : $@convention(thin) (@guaranteed String, @owned String) -> @owned String {
+bb0(%0 : $String, %1 : $String):
+  %2 = struct $S (%0 : $String, %1 : $String)
+  %3 = struct_extract %2 : $S, #S.b
+  return %3 : $String
+}
+
+// CHECK-LABEL: sil [ossa] @struct_extract_ossa
+// CHECK:         %2 = copy_value %0
+// CHECK:         return %2
+// CHECK:       } // end sil function 'struct_extract_ossa'
+sil [ossa] @struct_extract_ossa : $@convention(thin) (@guaranteed String, @guaranteed String) -> @owned String {
+bb0(%0 : @guaranteed $String, %1 : @guaranteed $String):
+  %2 = struct $S (%0 : $String, %1 : $String)
+  %3 = struct_extract %2 : $S, #S.a
+  %4 = copy_value %3 : $String
+  return %4 : $String
+}
+