[DEBUGINFO] Add option that allows to disable emission of flags in .loc directives.

Summary:
Some targets do not support extended format of .loc directive and
support only simple format: .loc <FileID> <Line> <Column>. Patch adds
MCAsmInfo flag and option that allows emit .loc directive without
additional flags.

Reviewers: echristo

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45184

llvm-svn: 329089

4 files changed, 112 insertions, 19 deletions

diff --git a/llvm/include/llvm/MC/MCAsmInfo.h b/llvm/include/llvm/MC/MCAsmInfo.h
index c538c46fc07..cb34fe3699c 100644
--- a/llvm/include/llvm/MC/MCAsmInfo.h
+++ b/llvm/include/llvm/MC/MCAsmInfo.h
@@ -344,6 +344,10 @@ protected:
   /// For example, foo(plt) instead of foo@plt.  Defaults to false.
   bool UseParensForSymbolVariant = false;
 
+  /// True if the target supports flags in ".loc" directive, false if only
+  /// location is allowed.
+  bool SupportsExtendedDwarfLocDirective = true;
+
   //===--- Prologue State ----------------------------------------------===//
 
   std::vector<MCCFIInstruction> InitialFrameState;
@@ -579,6 +583,9 @@ public:
   bool doDwarfFDESymbolsUseAbsDiff() const { return DwarfFDESymbolsUseAbsDiff; }
   bool useDwarfRegNumForCFI() const { return DwarfRegNumForCFI; }
   bool useParensForSymbolVariant() const { return UseParensForSymbolVariant; }
+  bool supportsExtendedDwarfLocDirective() const {
+    return SupportsExtendedDwarfLocDirective;
+  }
 
   void addInitialFrameState(const MCCFIInstruction &Inst) {
     InitialFrameState.push_back(Inst);
diff --git a/llvm/lib/MC/MCAsmInfo.cpp b/llvm/lib/MC/MCAsmInfo.cpp
index f05904048e0..30f22d2d68f 100644
--- a/llvm/lib/MC/MCAsmInfo.cpp
+++ b/llvm/lib/MC/MCAsmInfo.cpp
@@ -17,9 +17,18 @@
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCStreamer.h"
+#include "llvm/Support/CommandLine.h"
 
 using namespace llvm;
 
+enum DefaultOnOff { Default, Enable, Disable };
+static cl::opt<DefaultOnOff> DwarfExtendedLoc(
+    "dwarf-extended-loc", cl::Hidden,
+    cl::desc("Disable emission of the extended flags in .loc directives."),
+    cl::values(clEnumVal(Default, "Default for platform"),
+               clEnumVal(Enable, "Enabled"), clEnumVal(Disable, "Disabled")),
+    cl::init(Default));
+
 MCAsmInfo::MCAsmInfo() {
   SeparatorString = ";";
   CommentString = "#";
@@ -41,6 +50,8 @@ MCAsmInfo::MCAsmInfo() {
   Data64bitsDirective = "\t.quad\t";
   GlobalDirective = "\t.globl\t";
   WeakDirective = "\t.weak\t";
+  if (DwarfExtendedLoc != Default)
+    SupportsExtendedDwarfLocDirective = DwarfExtendedLoc == Enable;
 
   // FIXME: Clang's logic should be synced with the logic used to initialize
   //        this member and the two implementations should be merged.
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index c1d74a0e94a..01e1744b134 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -1171,28 +1171,30 @@ void MCAsmStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                                           unsigned Discriminator,
                                           StringRef FileName) {
   OS << "\t.loc\t" << FileNo << " " << Line << " " << Column;
-  if (Flags & DWARF2_FLAG_BASIC_BLOCK)
-    OS << " basic_block";
-  if (Flags & DWARF2_FLAG_PROLOGUE_END)
-    OS << " prologue_end";
-  if (Flags & DWARF2_FLAG_EPILOGUE_BEGIN)
-    OS << " epilogue_begin";
-
-  unsigned OldFlags = getContext().getCurrentDwarfLoc().getFlags();
-  if ((Flags & DWARF2_FLAG_IS_STMT) != (OldFlags & DWARF2_FLAG_IS_STMT)) {
-    OS << " is_stmt ";
+  if (MAI->supportsExtendedDwarfLocDirective()) {
+    if (Flags & DWARF2_FLAG_BASIC_BLOCK)
+      OS << " basic_block";
+    if (Flags & DWARF2_FLAG_PROLOGUE_END)
+      OS << " prologue_end";
+    if (Flags & DWARF2_FLAG_EPILOGUE_BEGIN)
+      OS << " epilogue_begin";
+
+    unsigned OldFlags = getContext().getCurrentDwarfLoc().getFlags();
+    if ((Flags & DWARF2_FLAG_IS_STMT) != (OldFlags & DWARF2_FLAG_IS_STMT)) {
+      OS << " is_stmt ";
+
+      if (Flags & DWARF2_FLAG_IS_STMT)
+        OS << "1";
+      else
+        OS << "0";
+    }
 
-    if (Flags & DWARF2_FLAG_IS_STMT)
-      OS << "1";
-    else
-      OS << "0";
+    if (Isa)
+      OS << " isa " << Isa;
+    if (Discriminator)
+      OS << " discriminator " << Discriminator;
   }
 
-  if (Isa)
-    OS << " isa " << Isa;
-  if (Discriminator)
-    OS << " discriminator " << Discriminator;
-
   if (IsVerboseAsm) {
     OS.PadToColumn(MAI->getCommentColumn());
     OS << MAI->getCommentString() << ' ' << FileName << ':'
diff --git a/llvm/test/DebugInfo/Generic/extended-loc-directive.ll b/llvm/test/DebugInfo/Generic/extended-loc-directive.ll
new file mode 100644
index 00000000000..2ffa7c6f91d
--- /dev/null
+++ b/llvm/test/DebugInfo/Generic/extended-loc-directive.ll
@@ -0,0 +1,73 @@
+; RUN: llc -filetype=asm -asm-verbose=0 -O0 -dwarf-extended-loc=Enable < %s | FileCheck %s --check-prefix ENABLED --check-prefix CHECK
+; RUN: llc -filetype=asm -asm-verbose=0 -O0 -dwarf-extended-loc=Disable < %s | FileCheck %s --check-prefix DISABLED --check-prefix CHECK
+
+; Check that the assembly output properly handles is_stmt changes. And since
+; we're testing anyway, check the integrated assembler too.
+
+; Generated with clang from multiline.c:
+; void f1();
+; void f2() {
+;   f1(); f1(); f1();
+;   f1(); f1(); f1();
+; }
+
+
+; CHECK: .loc 1 2 0{{$}}
+; CHECK-NOT: .loc{{ }}
+; ENABLED: .loc 1 3 3 prologue_end{{$}}
+; DISABLED: .loc 1 3 3{{$}}
+; CHECK-NOT: .loc
+; ENABLED: .loc 1 3 9 is_stmt 0{{$}}
+; DISABLED: .loc 1 3 9{{$}}
+; CHECK-NOT: .loc
+; CHECK: .loc 1 3 15{{$}}
+; CHECK-NOT: .loc
+; ENABLED: .loc 1 4 3 is_stmt 1{{$}}
+; DISABLED: .loc 1 4 3{{$}}
+; CHECK-NOT: .loc
+; ENABLED: .loc 1 4 9 is_stmt 0{{$}}
+; DISABLED: .loc 1 4 9{{$}}
+; CHECK-NOT: .loc
+; CHECK: .loc 1 4 15{{$}}
+; CHECK-NOT: .loc
+; ENABLED: .loc 1 5 1 is_stmt 1{{$}}
+; DISABLED: .loc 1 5 1{{$}}
+
+; Function Attrs: nounwind uwtable
+define void @f2() #0 !dbg !4 {
+entry:
+  call void (...) @f1(), !dbg !11
+  call void (...) @f1(), !dbg !12
+  call void (...) @f1(), !dbg !13
+  call void (...) @f1(), !dbg !14
+  call void (...) @f1(), !dbg !15
+  call void (...) @f1(), !dbg !16
+  ret void, !dbg !17
+}
+
+declare void @f1(...) #1
+
+attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.6.0 (trunk 225000) (llvm/trunk 224999)", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "multiline.c", directory: "/tmp/dbginfo")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "f2", line: 2, isLocal: false, isDefinition: true, isOptimized: false, unit: !0, scopeLine: 2, file: !1, scope: !5, type: !6, variables: !2)
+!5 = !DIFile(filename: "multiline.c", directory: "/tmp/dbginfo")
+!6 = !DISubroutineType(types: !7)
+!7 = !{null}
+!8 = !{i32 2, !"Dwarf Version", i32 4}
+!9 = !{i32 2, !"Debug Info Version", i32 3}
+!10 = !{!"clang version 3.6.0 (trunk 225000) (llvm/trunk 224999)"}
+!11 = !DILocation(line: 3, column: 3, scope: !4)
+!12 = !DILocation(line: 3, column: 9, scope: !4)
+!13 = !DILocation(line: 3, column: 15, scope: !4)
+!14 = !DILocation(line: 4, column: 3, scope: !4)
+!15 = !DILocation(line: 4, column: 9, scope: !4)
+!16 = !DILocation(line: 4, column: 15, scope: !4)
+!17 = !DILocation(line: 5, column: 1, scope: !4)