[SIL][Frontend] Simplify debug info generation flow for SIL files

 - If any of the `-g<kind>` flag is given -- except `-gnone`, debug
   info will be printed into every generated SIL files.
 - The `-gsil` is deprecated in favor of `-sil-based-debuginfo`. The
   SILDebugInfoGenerator Pass now generates intermediate SIL file with
   name "<output file>.sil_dbg_<n>.sil". Other functionalities of that
   Pass remain the same.

Author: mshockwave

CMakeLists.txt

@@ -374,7 +374,7 @@ option(SWIFT_RUNTIME_CLOBBER_FREED_OBJECTS
     "${SWIFT_RUNTIME_CLOBBER_FREED_OBJECTS_default}")
 
 option(SWIFT_STDLIB_SIL_DEBUGGING
-    "Compile the Swift standard library with -gsil to enable debugging and profiling on SIL level"
+    "Compile the Swift standard library with -sil-based-debuginfo to enable debugging and profiling on SIL level"
     FALSE)
 
 option(SWIFT_CHECK_INCREMENTAL_COMPILATION

docs/DebuggingTheCompiler.md

@@ -25,7 +25,7 @@ benefit of all Swift developers.
         - [Getting CommandLine for swift stdlib from Ninja to enable dumping stdlib SIL](#getting-commandline-for-swift-stdlib-from-ninja-to-enable-dumping-stdlib-sil)
         - [Dumping the SIL and other Data in LLDB](#dumping-the-sil-and-other-data-in-lldb)
     - [Debugging and Profiling on SIL level](#debugging-and-profiling-on-sil-level)
-        - [SIL source level profiling using -gsil](#sil-source-level-profiling-using--gsil)
+        - [SIL source level profiling using -sil-based-debuginfo](#sil-source-level-profiling)
         - [ViewCFG: Regex based CFG Printer for SIL/LLVM-IR](#viewcfg-regex-based-cfg-printer-for-silllvm-ir)
         - [Debugging the Compiler using advanced LLDB Breakpoints](#debugging-the-compiler-using-advanced-lldb-breakpoints)
         - [Debugging the Compiler using LLDB Scripts](#debugging-the-compiler-using-lldb-scripts)
@@ -101,6 +101,12 @@ swiftc -emit-sil -Onone file.swift
 swiftc -emit-sil -O file.swift
 ```
 
+* **Debug info in SIL** To print debug info from `file.swift` in SIL:
+
+```sh
+swiftc -g -emit-sil -O file.swift
+```
+
 * **IRGen** To print the LLVM IR after IR generation:
 
 ```sh
@@ -299,12 +305,13 @@ has a `dump()` method you can call.
 
 ## Debugging and Profiling on SIL level
 
-### SIL source level profiling using -gsil
+### SIL source level profiling
 
 The compiler provides a way to debug and profile on SIL level. To enable SIL
-debugging add the front-end option -gsil together with -g. Example:
+debugging add the front-end option -sil-based-debuginfo together with -g.
+Example:
 
-    swiftc -g -Xfrontend -gsil -O test.swift -o a.out
+    swiftc -g -Xfrontend -sil-based-debuginfo -O test.swift -o a.out
 
 This writes the SIL after optimizations into a file and generates debug info
 for it. In the debugger and profiler you can then see the SIL code instead of

include/swift/AST/SILOptions.h

@@ -145,7 +145,11 @@ class SILOptions {
   /// Don't generate code using partial_apply in SIL generation.
   bool DisableSILPartialApply = false;
 
-  /// The name of the SIL outputfile if compiled with SIL debugging (-gsil).
+  /// Print debug information into the SIL file
+  bool PrintDebugInfo = false;
+
+  /// The name of the SIL outputfile if compiled with SIL debugging
+  /// (-sil-based-debuginfo).
   std::string SILOutputFileNameForDebugging;
 
   /// If set to true, compile with the SIL Ownership Model enabled.

include/swift/Option/FrontendOptions.td

@@ -645,9 +645,11 @@ def print_inst_counts : Flag<["-"], "print-inst-counts">,
   HelpText<"Before IRGen, count all the various SIL instructions. Must be used "
            "in conjunction with -print-stats.">;
 
-def debug_on_sil : Flag<["-"], "gsil">,
+def debug_on_sil : Flag<["-"], "sil-based-debuginfo">,
   HelpText<"Write the SIL into a file and generate debug-info to debug on SIL "
            " level.">;
+def legacy_gsil : Flag<["-"], "gsil">,
+  HelpText<"Deprecated, use '-sil-based-debuginfo' instead">;
 
 def print_llvm_inline_tree : Flag<["-"], "print-llvm-inline-tree">,
   HelpText<"Print the LLVM inline tree.">;

include/swift/SIL/SILFunction.h

@@ -838,7 +838,8 @@ class SILFunction
     DeclCtxt = (DS ? DebugScope->Loc.getAsDeclContext() : nullptr);
   }
 
-  /// Initialize the debug scope for debug info on SIL level (-gsil).
+  /// Initialize the debug scope for debug info on SIL level
+  /// (-sil-based-debuginfo).
   void setSILDebugScope(const SILDebugScope *DS) {
     DebugScope = DS;
   }

include/swift/SIL/SILLocation.h

@@ -51,8 +51,9 @@ class SILLocation {
   /// Describes a position in a source file by explicitly storing the file name,
   /// line and column.
   ///
-  /// This is used for parsed locations from a SIL file, for "-gsil" (see
-  /// SILDebugInfoGenerator) and for the "compiler-generated" singleton location.
+  /// This is used for parsed locations from a SIL file, for
+  /// "-sil-based-debuginfo" (see SILDebugInfoGenerator) and for the
+  /// "compiler-generated" singleton location.
   /// In future we might also use it for de-serialized locations from a
   /// swiftmodule file.
   struct FilenameAndLocation : public SILAllocated<FilenameAndLocation> {

include/swift/SIL/SILPrintContext.h

@@ -78,7 +78,8 @@ class SILPrintContext {
 
   /// Constructor based on SILOptions.
   ///
-  /// DebugInfo will be set according to the -sil-print-debuginfo option.
+  /// DebugInfo will be set according to SILOptions::PrintDebugInfo or
+  /// the -sil-print-debuginfo option.
   SILPrintContext(llvm::raw_ostream &OS, const SILOptions &Opts);
 
   SILPrintContext(llvm::raw_ostream &OS, bool Verbose, bool SortedSIL,

lib/Frontend/CompilerInvocation.cpp

@@ -27,6 +27,7 @@
 #include "llvm/Support/LineIterator.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
+#include "llvm/Support/WithColor.h"
 
 using namespace swift;
 using namespace llvm::opt;
@@ -1360,6 +1361,16 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
   if (const Arg *A = Args.getLastArg(OPT_save_optimization_record_path))
     Opts.OptRecordFile = A->getValue();
 
+  // If any of the '-g<kind>', except '-gnone', is given,
+  // tell the SILPrinter to print debug info as well
+  if (const Arg *A = Args.getLastArg(OPT_g_Group)) {
+    if (!A->getOption().matches(options::OPT_gnone))
+      Opts.PrintDebugInfo = true;
+  }
+
+  if (Args.hasArg(OPT_legacy_gsil))
+    llvm::WithColor::warning() << "'-gsil' is deprecated, "
+                               << "use '-sil-based-debuginfo' instead\n";
   if (Args.hasArg(OPT_debug_on_sil)) {
     // Derive the name of the SIL file for debugging from
     // the regular outputfile.

lib/SIL/IR/SILPrinter.cpp

@@ -3637,7 +3637,8 @@ SILPrintContext::SILPrintContext(llvm::raw_ostream &OS, bool Verbose,
 
 SILPrintContext::SILPrintContext(llvm::raw_ostream &OS, const SILOptions &Opts)
     : OutStream(OS), Verbose(Opts.EmitVerboseSIL),
-      SortedSIL(Opts.EmitSortedSIL), DebugInfo(SILPrintDebugInfo),
+      SortedSIL(Opts.EmitSortedSIL),
+      DebugInfo(Opts.PrintDebugInfo || SILPrintDebugInfo),
       PrintFullConvention(Opts.PrintFullConvention) {}
 
 SILPrintContext::SILPrintContext(llvm::raw_ostream &OS, bool Verbose,

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -832,7 +832,7 @@ SILPassPipelinePlan::getPerformancePassPipeline(const SILOptions &Options) {
 
   addLastChanceOptPassPipeline(P);
 
-  // Has only an effect if the -gsil option is specified.
+  // Has only an effect if the -sil-based-debuginfo option is specified.
   addSILDebugInfoGeneratorPipeline(P);
 
   // Call the CFG viewer.
@@ -883,7 +883,7 @@ SILPassPipelinePlan::getOnonePassPipeline(const SILOptions &Options) {
   // Create pre-specializations.
   P.addOnonePrespecializations();
 
-  // Has only an effect if the -gsil option is specified.
+  // Has only an effect if the -sil-based-debuginfo option is specified.
   P.addSILDebugInfoGenerator();
 
   return P;