DebugInfo: Omit is_stmt from line table entries on the same line.

GCC does this for non-zero discriminators and since GCC doesn't produce
column info, that was the only place it comes up there. For LLVM, since
we can emit discriminators and/or column info, it makes more sense to
invert the condition and just test for changes in line number.

This should resolve at least some of the GDB 7.5 test suite failures
created by recent Clang changes that increase the location fidelity
(which, since Clang defaults to including column info on Linux by
default created a bunch of cases that confused GDB).

In theory we could do this better/differently by grouping actual source
statements together in a similar manner to the way lexical scopes are
handled but given that GDB isn't really in a position to consume that (&
users are probably somewhat used to different lines being different
'statements') this seems the safest and cheapest change. (I'm concerned
that doing this 'right' would bloat the debugloc data even further -
something Duncan's working hard to address)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225011 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 87 insertions, 4 deletions

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 5413c9b5aff..52d6175d3d3 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1026,8 +1026,10 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
       if (DL == PrologEndLoc) {
         Flags |= DWARF2_FLAG_PROLOGUE_END;
         PrologEndLoc = DebugLoc();
+        Flags |= DWARF2_FLAG_IS_STMT;
       }
-      if (PrologEndLoc.isUnknown())
+      if (DL.getLine() !=
+          Asm->OutStreamer.getContext().getCurrentDwarfLoc().getLine())
         Flags |= DWARF2_FLAG_IS_STMT;
 
       if (!DL.isUnknown()) {
diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index a1233929615..f88b3a068dd 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -872,8 +872,6 @@ void MCAsmStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                                           unsigned Isa,
                                           unsigned Discriminator,
                                           StringRef FileName) {
-  this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
-                                          Isa, Discriminator, FileName);
   OS << "\t.loc\t" << FileNo << " " << Line << " " << Column;
   if (Flags & DWARF2_FLAG_BASIC_BLOCK)
     OS << " basic_block";
@@ -903,6 +901,8 @@ void MCAsmStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
        << Line << ':' << Column;
   }
   EmitEOL();
+  this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
+                                          Isa, Discriminator, FileName);
 }
 
 MCSymbol *MCAsmStreamer::getDwarfLineTableSymbol(unsigned CUID) {
diff --git a/test/DebugInfo/X86/discriminator.ll b/test/DebugInfo/X86/discriminator.ll
index d43c05acdf8..0f4a84d2207 100644
--- a/test/DebugInfo/X86/discriminator.ll
+++ b/test/DebugInfo/X86/discriminator.ll
@@ -60,4 +60,4 @@ attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointe
 
 ; CHECK: Address            Line   Column File   ISA Discriminator Flags
 ; CHECK: ------------------ ------ ------ ------ --- ------------- -------------
-; CHECK: 0x0000000000000011      2      0      1   0            42  is_stmt
+; CHECK: 0x0000000000000011      2      0      1   0            42 {{$}}
diff --git a/test/DebugInfo/multiline.ll b/test/DebugInfo/multiline.ll
new file mode 100644
index 00000000000..ada34ca9c24
--- /dev/null
+++ b/test/DebugInfo/multiline.ll
@@ -0,0 +1,81 @@
+; RUN: llc -filetype=asm -O0 < %s | FileCheck %s
+; RUN: llc -filetype=obj -O0 < %s | llvm-dwarfdump -debug-dump=line - | FileCheck %s --check-prefix=INT
+
+; Check that the assembly output properly handles is_stmt changes. And since
+; we're testing anyway, check the integrated assembler too.
+
+; Generated with clang from multiline.c:
+; void f1();
+; void f2() {
+;   f1(); f1(); f1();
+;   f1(); f1(); f1();
+; }
+
+
+; CHECK: .loc	1 2 0 #
+; CHECK-NOT: .loc
+; CHECK: .loc	1 3 3 prologue_end #
+; CHECK-NOT: .loc
+; CHECK: .loc	1 3 9 is_stmt 0 #
+; CHECK-NOT: .loc
+; CHECK: .loc	1 3 15 #
+; CHECK-NOT: .loc
+; CHECK: .loc	1 4 3 is_stmt 1 #
+; CHECK-NOT: .loc
+; CHECK: .loc	1 4 9 is_stmt 0 #
+; CHECK-NOT: .loc
+; CHECK: .loc	1 4 15 #
+; CHECK-NOT: .loc
+; CHECK: .loc	1 5 1 is_stmt 1 #
+
+; INT: {{^}}Address
+; INT: -----
+; INT-NEXT: 2 0 1 0 0 is_stmt{{$}}
+; INT-NEXT: 3 3 1 0 0 is_stmt prologue_end{{$}}
+; INT-NEXT: 3 9 1 0 0 {{$}}
+; INT-NEXT: 3 15 1 0 0 {{$}}
+; INT-NEXT: 4 3 1 0 0 is_stmt{{$}}
+; INT-NEXT: 4 9 1 0 0 {{$}}
+; INT-NEXT: 4 15 1 0 0 {{$}}
+; INT-NEXT: 5 1 1 0 0 is_stmt{{$}}
+
+
+; Function Attrs: nounwind uwtable
+define void @f2() #0 {
+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 = !{!"0x11\0012\00clang version 3.6.0 (trunk 225000) (llvm/trunk 224999)\000\00\000\00\001", !1, !2, !2, !3, !2, !2} ; [ DW_TAG_compile_unit ] [/tmp/dbginfo/multiline.c] [DW_LANG_C99]
+!1 = !{!"multiline.c", !"/tmp/dbginfo"}
+!2 = !{}
+!3 = !{!4}
+!4 = !{!"0x2e\00f2\00f2\00\002\000\001\000\000\000\000\002", !1, !5, !6, null, void ()* @f2, null, null, !2} ; [ DW_TAG_subprogram ] [line 2] [def] [f2]
+!5 = !{!"0x29", !1}                               ; [ DW_TAG_file_type ] [/tmp/dbginfo/multiline.c]
+!6 = !{!"0x15\00\000\000\000\000\000\000", null, null, null, !7, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = !{null}
+!8 = !{i32 2, !"Dwarf Version", i32 4}
+!9 = !{i32 2, !"Debug Info Version", i32 2}
+!10 = !{!"clang version 3.6.0 (trunk 225000) (llvm/trunk 224999)"}
+!11 = !{i32 3, i32 3, !4, null}
+!12 = !{i32 3, i32 9, !4, null}
+!13 = !{i32 3, i32 15, !4, null}
+!14 = !{i32 4, i32 3, !4, null}
+!15 = !{i32 4, i32 9, !4, null}
+!16 = !{i32 4, i32 15, !4, null}
+!17 = !{i32 5, i32 1, !4, null}