libswift: add an example SILPrinter pass.

SILPrinter prints the SIL of a function.
It's and example pass which demonstrates the basic SIL API of libswift.

Author: eeckstein

include/swift/SILOptimizer/PassManager/Passes.def

@@ -339,6 +339,8 @@ PASS(SILDebugInfoGenerator, "sil-debuginfo-gen",
      "Generate Debug Information with Source Locations into Textual SIL")
 PASS(EarlySROA, "early-sroa",
      "Scalar Replacement of Aggregate Stack Objects on high-level SIL")
+SWIFT_FUNCTION_PASS(SILPrinter, "sil-printer",
+     "Test pass which prints the SIL of a function")
 PASS(SROA, "sroa",
      "Scalar Replacement of Aggregate Stack Objects")
 PASS(SROABBArgs, "sroa-bb-args",

libswift/Sources/Optimizer/CMakeLists.txt

@@ -10,3 +10,4 @@ add_libswift_module(Optimizer
     DEPENDS SIL)
 
 add_subdirectory(PassManager)
+add_subdirectory(FunctionPasses)

libswift/Sources/Optimizer/FunctionPasses/CMakeLists.txt

@@ -0,0 +1,11 @@
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See http://swift.org/LICENSE.txt for license information
+# See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+
+libswift_sources(Optimizer
+  SILPrinter.swift
+)

libswift/Sources/Optimizer/FunctionPasses/SILPrinter.swift

@@ -0,0 +1,45 @@
+//===--- SILPrinter.swift - Example swift function pass -------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2021 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
+
+let silPrinterPass = FunctionPass(name: "sil-printer", runSILPrinter)
+
+func runSILPrinter(function: Function, context: FunctionPassContext) {
+  print("run SILPrinter on function: \(function.name)")
+
+  for (bbIdx, block) in function.blocks.enumerated() {
+    print("bb\(bbIdx):")
+
+    print("  arguments:")
+    for arg in block.arguments {
+      print("    arg: \(arg)")
+      for use in arg.uses {
+        print("      user: \(use.instruction)")
+      }
+    }
+
+    print("  instructions:")
+    for inst in block.instructions {
+      print("  \(inst)")
+      for op in inst.operands {
+        print("      op: \(op.value)")
+      }
+      for (resultIdx, result) in inst.results.enumerated() {
+        for use in result.uses {
+          print("      user of result \(resultIdx): \(use.instruction)")
+        }
+      }
+    }
+    print()
+  }
+}

libswift/Sources/Optimizer/PassManager/PassRegistration.swift

@@ -28,4 +28,5 @@ private func registerPass(
 }
 
 private func registerSwiftPasses() {
+  registerPass(silPrinterPass, { silPrinterPass.run($0) })
 }