Merge pull request swiftlang#28008 from adrian-prantl/nodebug

Add a hidden option to disable debugger shadow copies.

Author: adrian-prantl

include/swift/AST/IRGenOptions.h

@@ -209,6 +209,10 @@ class IRGenOptions {
   /// Disable round-trip verification of mangled debug types.
   unsigned DisableRoundTripDebugTypes : 1;
 
+  /// Whether to disable shadow copies for local variables on the stack. This is
+  /// only used for testing.
+  unsigned DisableDebuggerShadowCopies : 1;
+
   /// Path to the profdata file to be used for PGO, or the empty string.
   std::string UseProfile = "";
 
@@ -237,8 +241,7 @@ class IRGenOptions {
         Sanitizers(OptionSet<SanitizerKind>()),
         DebugInfoLevel(IRGenDebugInfoLevel::None),
         DebugInfoFormat(IRGenDebugInfoFormat::None),
-        DisableClangModuleSkeletonCUs(false),
-        UseJIT(false),
+        DisableClangModuleSkeletonCUs(false), UseJIT(false),
         IntegratedREPL(false), DisableLLVMOptzns(false),
         DisableSwiftSpecificLLVMOptzns(false), DisableLLVMSLPVectorizer(false),
         DisableFPElim(true), Playground(false), EmitStackPromotionChecks(false),
@@ -250,8 +253,8 @@ class IRGenOptions {
         LazyInitializeProtocolConformances(false), DisableLegacyTypeInfo(false),
         UseIncrementalLLVMCodeGen(true), UseSwiftCall(false),
         GenerateProfile(false), EnableDynamicReplacementChaining(false),
-        DisableRoundTripDebugTypes(false), CmdArgs(),
-        SanitizeCoverage(llvm::SanitizerCoverageOptions()),
+        DisableRoundTripDebugTypes(false), DisableDebuggerShadowCopies(false),
+        CmdArgs(), SanitizeCoverage(llvm::SanitizerCoverageOptions()),
         TypeInfoFilter(TypeInfoDumpFilter::All) {}
 
   /// Appends to \p os an arbitrary string representing all options which

include/swift/Option/FrontendOptions.td

@@ -453,6 +453,11 @@ def debugger_testing_transform : Flag<["-"], "debugger-testing-transform">,
   HelpText<"Instrument the code with calls to an intrinsic that record the expected values of "
            "local variables so they can be compared against the results from the debugger.">;
 
+def disable_debugger_shadow_copies : Flag<["-"], "disable-debugger-shadow-copies">,
+  HelpText<"Disable debugger shadow copies of local variables."
+           "This option is only useful for testing the compiler.">,
+  Flags<[FrontendOption, HelpHidden]>;
+
 def playground : Flag<["-"], "playground">,
   HelpText<"Apply the playground semantics and transformation">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -1078,6 +1078,9 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
   if (Args.hasArg(OPT_no_clang_module_breadcrumbs))
     Opts.DisableClangModuleSkeletonCUs = true;
 
+  if (Args.hasArg(OPT_disable_debugger_shadow_copies))
+    Opts.DisableDebuggerShadowCopies = true;
+
   if (Args.hasArg(OPT_use_jit))
     Opts.UseJIT = true;
 

lib/IRGen/IRGenSIL.cpp

@@ -787,7 +787,8 @@ class IRGenSILFunction :
                                       Alignment Align = Alignment(0)) {
     // Never emit shadow copies when optimizing, or if already on the stack.
     // No debug info is emitted for refcounts either.
-    if (IGM.IRGen.Opts.shouldOptimize() || IsAnonymous ||
+    if (IGM.IRGen.Opts.DisableDebuggerShadowCopies ||
+        IGM.IRGen.Opts.shouldOptimize() || IsAnonymous ||
         isa<llvm::AllocaInst>(Storage) || isa<llvm::UndefValue>(Storage) ||
         Storage->getType() == IGM.RefCountedPtrTy)
       return Storage;
@@ -830,7 +831,8 @@ class IRGenSILFunction :
     Explosion e = getLoweredExplosion(SILVal);
 
     // Only do this at -O0.
-    if (IGM.IRGen.Opts.shouldOptimize() || IsAnonymous) {
+    if (IGM.IRGen.Opts.DisableDebuggerShadowCopies ||
+        IGM.IRGen.Opts.shouldOptimize() || IsAnonymous) {
       auto vals = e.claimAll();
       copy.append(vals.begin(), vals.end());
       return;
@@ -4009,7 +4011,8 @@ void IRGenSILFunction::emitDebugInfoForAllocStack(AllocStackInst *i,
          isa<llvm::IntrinsicInst>(addr));
 
   auto Indirection = DirectValue;
-  if (!IGM.IRGen.Opts.shouldOptimize())
+  if (!IGM.IRGen.Opts.DisableDebuggerShadowCopies &&
+      !IGM.IRGen.Opts.shouldOptimize())
     if (auto *Alloca = dyn_cast<llvm::AllocaInst>(addr))
       if (!Alloca->isStaticAlloca()) {
         // Store the address of the dynamic alloca on the stack.

test/DebugInfo/shadow_copies.swift

@@ -1,5 +1,6 @@
 // RUN: %target-swift-frontend %s -Onone -emit-ir -g -o - | %FileCheck %s
-
+// RUN: %target-swift-frontend %s -Onone -emit-ir -g -o - \
+// RUN:   -disable-debugger-shadow-copies | %FileCheck %s --check-prefix=NOCOPY
 class ClassA
 {
     var x : Int64
@@ -16,11 +17,17 @@ class ClassB : ClassA
 {
     override init (_ input : Int64)
     {
-    // CHECK: @"$s{{.*}}6ClassBCyACs5Int64Vcfc"
-    // CHECK:  alloca {{.*}}ClassBC*
-    // CHECK:  alloca i64
-    // CHECK-NOT: alloca
-    // CHECK: ret {{.*}}ClassBC
+    // CHECK:       @"$s{{.*}}6ClassBCyACs5Int64Vcfc"
+    // NOPCOPY:     @"$s{{.*}}6ClassBCyACs5Int64Vcfc"
+    // CHECK:       alloca {{.*}}ClassBC*
+    // NOPCOPY:     alloca {{.*}}ClassBC*
+
+    // CHECK:       alloca i64
+
+    // CHECK-NOT:   alloca
+    // NOPCOPY-NOT: alloca
+    // CHECK:       ret {{.*}}ClassBC
+    // NOCOPY:      ret {{.*}}ClassBC
         super.init (input)
     }
 }