Add new debug kind LocTrackingOnly.

Summary:
This new debug emission kind supports emitting line location
information in all instructions, but stops code generation
from emitting debug info to the final output.

This mode is useful when the backend wants to track source
locations during code generation, but it does not want to
produce debug info. This is currently used by optimization
remarks (-Rpass, -Rpass-missed and -Rpass-analysis).

When one of the -Rpass flags is used, the front end will enable
location tracking, only if no other debug option is enabled.

To prevent debug information from being generated, a new debug
info kind LocTrackingOnly causes DIBuilder::createCompileUnit() to
not emit the llvm.dbg.cu annotation. This blocks final code generation
from generating debug info in the back end.

Depends on D4234.

Reviewers: echristo, dblaikie

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4235

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211610 91177308-0d34-0410-b5e6-96231b3b80d8

docs/UsersManual.rst

@@ -577,12 +577,10 @@ feature.
 Current limitations
 ^^^^^^^^^^^^^^^^^^^
 
-1. For :option:`-Rpass` to provide source location information, you
-   need to enable debug line tables and column information. That is,
-   you need to add :option:`-gmlt` (or any of the debug-generating
-   flags) and :option:`-gcolumn-info`. If you omit these options,
-   every remark will be accompanied by a note stating that line number
-   information is missing.
+1. For :option:`-Rpass` to provide column information, you
+   need to enable it explicitly. That is, you need to add
+   :option:`-gcolumn-info`. If you omit this, remarks will only show
+   line information.
 
 2. Optimization remarks that refer to function names will display the
    mangled name of the function. Since these remarks are emitted by the

include/clang/Basic/DiagnosticFrontendKinds.td

@@ -41,9 +41,6 @@ def remark_fe_backend_optimization_remark_missed : Remark<"%0">, BackendInfo,
     InGroup<BackendOptimizationRemarkMissed>, DefaultRemark;
 def remark_fe_backend_optimization_remark_analysis : Remark<"%0">, BackendInfo,
     InGroup<BackendOptimizationRemarkAnalysis>, DefaultRemark;
-def note_fe_backend_optimization_remark_missing_loc : Note<"use "
-  "-gline-tables-only -gcolumn-info to track source location information "
-  "for this optimization remark">;
 def note_fe_backend_optimization_remark_invalid_loc : Note<"could "
   "not determine the original source location for %0:%1:%2">;
 

include/clang/Frontend/CodeGenOptions.def

@@ -140,7 +140,7 @@ VALUE_CODEGENOPT(NumRegisterParameters, 32, 0)
 VALUE_CODEGENOPT(SSPBufferSize, 32, 0)
 
 /// The kind of generated debug info.
-ENUM_CODEGENOPT(DebugInfo, DebugInfoKind, 2, NoDebugInfo)
+ENUM_CODEGENOPT(DebugInfo, DebugInfoKind, 3, NoDebugInfo)
 
 /// Dwarf version.
 VALUE_CODEGENOPT(DwarfVersion, 3, 0)

include/clang/Frontend/CodeGenOptions.h

@@ -53,6 +53,13 @@ public:
   enum DebugInfoKind {
     NoDebugInfo,          /// Don't generate debug info.
 
+    LocTrackingOnly,      /// Emit location information but do not generate
+                          /// debug info in the output. This is useful in
+                          /// cases where the backend wants to track source
+                          /// locations for instructions without actually
+                          /// emitting debug info for them (e.g., when -Rpass
+                          /// is used).
+
     DebugLineTablesOnly,  /// Emit only debug info necessary for generating
                           /// line number tables (-gline-tables-only).
 

lib/CodeGen/CGDebugInfo.cpp

@@ -375,9 +375,10 @@ void CGDebugInfo::CreateCompileUnit() {
   TheCU = DBuilder.createCompileUnit(
       LangTag, Filename, getCurrentDirname(), Producer, LO.Optimize,
       CGM.getCodeGenOpts().DwarfDebugFlags, RuntimeVers, SplitDwarfFilename,
-      DebugKind == CodeGenOptions::DebugLineTablesOnly
+      DebugKind <= CodeGenOptions::DebugLineTablesOnly
           ? llvm::DIBuilder::LineTablesOnly
-          : llvm::DIBuilder::FullDebug);
+          : llvm::DIBuilder::FullDebug,
+      DebugKind != CodeGenOptions::LocTrackingOnly);
 }
 
 /// CreateType - Get the Basic type from the cache or create a new
@@ -2341,7 +2342,7 @@ llvm::DIScope CGDebugInfo::getDeclarationOrDefinition(const Decl *D) {
 /// getFunctionDeclaration - Return debug info descriptor to describe method
 /// declaration for the given method definition.
 llvm::DISubprogram CGDebugInfo::getFunctionDeclaration(const Decl *D) {
-  if (!D || DebugKind == CodeGenOptions::DebugLineTablesOnly)
+  if (!D || DebugKind <= CodeGenOptions::DebugLineTablesOnly)
     return llvm::DISubprogram();
 
   const FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
@@ -2386,7 +2387,7 @@ llvm::DISubprogram CGDebugInfo::getFunctionDeclaration(const Decl *D) {
 llvm::DICompositeType CGDebugInfo::getOrCreateFunctionType(const Decl *D,
                                                            QualType FnType,
                                                            llvm::DIFile F) {
-  if (!D || DebugKind == CodeGenOptions::DebugLineTablesOnly)
+  if (!D || DebugKind <= CodeGenOptions::DebugLineTablesOnly)
     // Create fake but valid subroutine type. Otherwise
     // llvm::DISubprogram::Verify() would return false, and
     // subprogram DIE will miss DW_AT_decl_file and

lib/CodeGen/CodeGenAction.cpp

@@ -443,15 +443,7 @@ void BackendConsumer::EmitOptimizationRemark(
   Diags.Report(Loc, DiagID) << AddFlagValue(D.getPassName())
                             << D.getMsg().str();
 
-  if (Line == 0)
-    // If we could not extract a source location for the diagnostic,
-    // inform the user how they can get source locations back.
-    //
-    // FIXME: We should really be generating !srcloc annotations when
-    // -Rpass is used. !srcloc annotations need to be emitted in
-    // approximately the same spots as !dbg nodes.
-    Diags.Report(Loc, diag::note_fe_backend_optimization_remark_missing_loc);
-  else if (DILoc.isInvalid())
+  if (DILoc.isInvalid())
     // If we were not able to translate the file:line:col information
     // back to a SourceLocation, at least emit a note stating that
     // we could not translate this location. This can happen in the

lib/Frontend/CompilerInvocation.cpp

@@ -550,18 +550,30 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   }
 
   Opts.DependentLibraries = Args.getAllArgValues(OPT_dependent_lib);
+  bool NeedLocTracking = false;
 
-  if (Arg *A = Args.getLastArg(OPT_Rpass_EQ))
+  if (Arg *A = Args.getLastArg(OPT_Rpass_EQ)) {
     Opts.OptimizationRemarkPattern =
         GenerateOptimizationRemarkRegex(Diags, Args, A);
+    NeedLocTracking = true;
+  }
 
-  if (Arg *A = Args.getLastArg(OPT_Rpass_missed_EQ))
+  if (Arg *A = Args.getLastArg(OPT_Rpass_missed_EQ)) {
     Opts.OptimizationRemarkMissedPattern =
         GenerateOptimizationRemarkRegex(Diags, Args, A);
+    NeedLocTracking = true;
+  }
 
-  if (Arg *A = Args.getLastArg(OPT_Rpass_analysis_EQ))
+  if (Arg *A = Args.getLastArg(OPT_Rpass_analysis_EQ)) {
     Opts.OptimizationRemarkAnalysisPattern =
         GenerateOptimizationRemarkRegex(Diags, Args, A);
+    NeedLocTracking = true;
+  }
+
+  // If the user requested one of the flags in the -Rpass family, make sure
+  // that the backend tracks source location information.
+  if (NeedLocTracking && Opts.getDebugInfo() == CodeGenOptions::NoDebugInfo)
+    Opts.setDebugInfo(CodeGenOptions::LocTrackingOnly);
 
   return Success;
 }

test/Frontend/optimization-remark.c

@@ -3,8 +3,18 @@
 // always trigger the inliner, so it should be independent of the
 // optimization level.
 
-// RUN: %clang_cc1 %s -Rpass=inline -Rpass-analysis=inline -Rpass-missed=inline -O0 -gline-tables-only -emit-llvm-only -verify
+// RUN: %clang_cc1 %s -Rpass=inline -Rpass-analysis=inline -Rpass-missed=inline -O0 -emit-llvm-only -verify
 // RUN: %clang_cc1 %s -DNDEBUG -Rpass=inline -emit-llvm-only -verify
+// RUN: %clang_cc1 %s -Rpass=inline -emit-llvm -o %t 2>/dev/null | FileCheck %s < %t
+
+// -Rpass should produce source location annotations, exclusively (just
+// like -gmlt).
+// CHECK: , !dbg !
+// CHECK-NOT: DW_TAG_base_type
+
+// But llvm.dbg.cu should be missing (to prevent writing debug info to
+// the final output).
+// CHECK-NOT: !llvm.dbg.cu = !{
 
 int foo(int x, int y) __attribute__((always_inline));
 int foo(int x, int y) { return x + y; }
@@ -27,5 +37,5 @@ int bar(int j) {
   return foo(j, j - 2) * foz(j - 2, j);
 }
 #ifdef NDEBUG
-// expected-remark@-2 {{foo inlined into bar}} expected-note@-2 {{use -gline-tables-only -gcolumn-info to track source location information for this optimization remark}}
+// expected-remark@-3 {{foo inlined into bar}}
 #endif