Debug info: Emit values in subregisters that do not have a separate

DWARF register number by emitting a super-register + DW_OP_bit_piece.
This is necessary because on x86_64, there are no DWARF register numbers
for i386-style subregisters.
Fixes a bunch of FIXMEs.

rdar://problem/16015314

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201180 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 175 insertions, 5 deletions

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index bab8aad497f..09aedc4cc93 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -868,12 +868,14 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc,
                                 bool Indirect) const {
   const TargetRegisterInfo *TRI = TM.getRegisterInfo();
   int Reg = TRI->getDwarfRegNum(MLoc.getReg(), false);
+  bool isSubRegister = Reg < 0;
+  unsigned Idx = 0;
 
   for (MCSuperRegIterator SR(MLoc.getReg(), TRI); SR.isValid() && Reg < 0;
        ++SR) {
     Reg = TRI->getDwarfRegNum(*SR, false);
-    // FIXME: Get the bit range this register uses of the superregister
-    // so that we can produce a DW_OP_bit_piece
+    if (Reg >= 0)
+      Idx = TRI->getSubRegIndex(*SR, MLoc.getReg());
   }
 
   // FIXME: Handle cases like a super register being encoded as
@@ -910,7 +912,24 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc,
     }
   }
 
-  // FIXME: Produce a DW_OP_bit_piece if we used a superregister
+  // Emit Mask
+  if (isSubRegister) {
+    unsigned Size = TRI->getSubRegIdxSize(Idx);
+    unsigned Offset = TRI->getSubRegIdxOffset(Idx);
+    if (Offset > 0) {
+      OutStreamer.AddComment("DW_OP_bit_piece");
+      EmitInt8(dwarf::DW_OP_bit_piece);
+      OutStreamer.AddComment(Twine(Size));
+      EmitULEB128(Size);
+      OutStreamer.AddComment(Twine(Offset));
+      EmitULEB128(Offset);
+    } else {
+      OutStreamer.AddComment("DW_OP_piece");
+      EmitInt8(dwarf::DW_OP_piece);
+      OutStreamer.AddComment(Twine(Size));
+      EmitULEB128(Size);
+    }
+  }
 }
 
 bool AsmPrinter::doFinalization(Module &M) {
diff --git a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index a1db1e0a2ed..6c9e40b0668 100644
--- a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -24,6 +24,7 @@
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/Support/CommandLine.h"
@@ -476,13 +477,45 @@ void DwarfUnit::addVariableAddress(const DbgVariable &DV, DIE *Die,
 /// addRegisterOp - Add register operand.
 void DwarfUnit::addRegisterOp(DIEBlock *TheDie, unsigned Reg) {
   const TargetRegisterInfo *RI = Asm->TM.getRegisterInfo();
-  unsigned DWReg = RI->getDwarfRegNum(Reg, false);
+  int DWReg = RI->getDwarfRegNum(Reg, false);
+  bool isSubRegister = DWReg < 0;
+
+  unsigned Idx = 0;
+
+  // Go up the super-register chain until we hit a valid dwarf register number.
+  for (MCSuperRegIterator SR(Reg, RI); SR.isValid() && DWReg < 0; ++SR) {
+    DWReg = RI->getDwarfRegNum(*SR, false);
+    if (DWReg >= 0)
+      Idx = RI->getSubRegIndex(*SR, Reg);
+  }
+
+  if (DWReg < 0) {
+    DEBUG(llvm::dbgs() << "Invalid Dwarf register number.\n");
+    addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_nop);
+    return;
+  }
+
+  // Emit register
   if (DWReg < 32)
     addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_reg0 + DWReg);
   else {
     addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_regx);
     addUInt(TheDie, dwarf::DW_FORM_udata, DWReg);
   }
+
+  // Emit Mask
+  if (isSubRegister) {
+    unsigned Size = RI->getSubRegIdxSize(Idx);
+    unsigned Offset = RI->getSubRegIdxOffset(Idx);
+    if (Offset > 0) {
+      addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_bit_piece);
+      addUInt(TheDie, dwarf::DW_FORM_data1, Size);
+      addUInt(TheDie, dwarf::DW_FORM_data1, Offset);
+    } else {
+      addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_piece);
+      addUInt(TheDie, dwarf::DW_FORM_data1, Size);
+    }
+  }
 }
 
 /// addRegisterOffset - Add register offset.
diff --git a/test/DebugInfo/X86/subreg.ll b/test/DebugInfo/X86/subreg.ll
index 162c2d166d7..58e3bfc3bc3 100644
--- a/test/DebugInfo/X86/subreg.ll
+++ b/test/DebugInfo/X86/subreg.ll
@@ -2,9 +2,10 @@
 
 ; We are testing that a value in a 16 bit register gets reported as
 ; being in its superregister.
-; FIXME: There should be a DW_OP_bit_piece too.
 
 ; CHECK: .byte   80                      # DW_OP_reg0
+; CHECK: .byte   147                     # DW_OP_piece
+; CHECK: .byte   16                      # 16
 
 define i16 @f(i16 signext %zzz) nounwind {
 entry:
diff --git a/test/DebugInfo/X86/subregisters.ll b/test/DebugInfo/X86/subregisters.ll
new file mode 100644
index 00000000000..ac0c3839869
--- /dev/null
+++ b/test/DebugInfo/X86/subregisters.ll
@@ -0,0 +1,117 @@
+; RUN: llc -mtriple=x86_64-apple-darwin %s -o %t.o -filetype=obj -O0
+; RUN: llvm-dwarfdump %t.o | FileCheck %s
+;
+; Test that on x86_64, the 32-bit subregister esi is emitted as
+; DW_OP_piece 32 of the 64-bit rsi.
+;
+; rdar://problem/16015314
+;
+; CHECK:  DW_AT_name [DW_FORM_strp]{{.*}} "a"
+; CHECK:    DW_AT_location [DW_FORM_block1]       (<0x03> 54 93 20 )
+;
+; struct bar {
+;   int a;
+;   int b;
+; };
+;
+; void doSomething() __attribute__ ((noinline));
+;
+; void doSomething(struct bar *b)
+; {
+;   int a = b->a;
+;   printf("%d\n", a); // set breakpoint here
+; }
+;
+; int main()
+; {
+;   struct bar myBar = { 3, 4 };
+;   doSomething(&myBar);
+;   return 0;
+; }
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9.0"
+
+%struct.bar = type { i32, i32 }
+
+@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
+@main.myBar = private unnamed_addr constant %struct.bar { i32 3, i32 4 }, align 4
+
+; Function Attrs: noinline nounwind ssp uwtable
+define void @doSomething(%struct.bar* nocapture readonly %b) #0 {
+entry:
+  tail call void @llvm.dbg.value(metadata !{%struct.bar* %b}, i64 0, metadata !15), !dbg !25
+  %a1 = getelementptr inbounds %struct.bar* %b, i64 0, i32 0, !dbg !26
+  %0 = load i32* %a1, align 4, !dbg !26, !tbaa !27
+  tail call void @llvm.dbg.value(metadata !{i32 %0}, i64 0, metadata !16), !dbg !26
+  %call = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i32 %0) #4, !dbg !32
+  ret void, !dbg !33
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata) #1
+
+; Function Attrs: nounwind
+declare i32 @printf(i8* nocapture readonly, ...) #2
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @main() #3 {
+entry:
+  %myBar = alloca i64, align 8, !dbg !34
+  %tmpcast = bitcast i64* %myBar to %struct.bar*, !dbg !34
+  tail call void @llvm.dbg.declare(metadata !{%struct.bar* %tmpcast}, metadata !21), !dbg !34
+  store i64 17179869187, i64* %myBar, align 8, !dbg !34
+  call void @doSomething(%struct.bar* %tmpcast), !dbg !35
+  ret i32 0, !dbg !36
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata) #1
+
+attributes #0 = { noinline nounwind ssp uwtable }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind }
+attributes #3 = { nounwind ssp uwtable }
+attributes #4 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!22, !23}
+!llvm.ident = !{!24}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5 ", i1 true, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [subregisters.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"subregisters.c", metadata !""}
+!2 = metadata !{}
+!3 = metadata !{metadata !4, metadata !17}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"doSomething", metadata !"doSomething", metadata !"", i32 10, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 true, void (%struct.bar*)* @doSomething, null, null, metadata !14, i32 11} ; [ DW_TAG_subprogram ] [line 10] [def] [scope 11] [doSomething]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [subregisters.c]
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{null, metadata !8}
+!8 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, metadata !9} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from bar]
+!9 = metadata !{i32 786451, metadata !1, null, metadata !"bar", i32 3, i64 64, i64 32, i32 0, i32 0, null, metadata !10, i32 0, null, null, null} ; [ DW_TAG_structure_type ] [bar] [line 3, size 64, align 32, offset 0] [def] [from ]
+!10 = metadata !{metadata !11, metadata !13}
+!11 = metadata !{i32 786445, metadata !1, metadata !9, metadata !"a", i32 4, i64 32, i64 32, i64 0, i32 0, metadata !12} ; [ DW_TAG_member ] [a] [line 4, size 32, align 32, offset 0] [from int]
+!12 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!13 = metadata !{i32 786445, metadata !1, metadata !9, metadata !"b", i32 5, i64 32, i64 32, i64 32, i32 0, metadata !12} ; [ DW_TAG_member ] [b] [line 5, size 32, align 32, offset 32] [from int]
+!14 = metadata !{metadata !15, metadata !16}
+!15 = metadata !{i32 786689, metadata !4, metadata !"b", metadata !5, i32 16777226, metadata !8, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [b] [line 10]
+!16 = metadata !{i32 786688, metadata !4, metadata !"a", metadata !5, i32 12, metadata !12, i32 0, i32 0} ; [ DW_TAG_auto_variable ] [a] [line 12]
+!17 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"main", metadata !"main", metadata !"", i32 16, metadata !18, i1 false, i1 true, i32 0, i32 0, null, i32 0, i1 true, i32 ()* @main, null, null, metadata !20, i32 17} ; [ DW_TAG_subprogram ] [line 16] [def] [scope 17] [main]
+!18 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !19, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!19 = metadata !{metadata !12}
+!20 = metadata !{metadata !21}
+!21 = metadata !{i32 786688, metadata !17, metadata !"myBar", metadata !5, i32 18, metadata !9, i32 0, i32 0} ; [ DW_TAG_auto_variable ] [myBar] [line 18]
+!22 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
+!23 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!24 = metadata !{metadata !"clang version 3.5 "}
+!25 = metadata !{i32 10, i32 0, metadata !4, null}
+!26 = metadata !{i32 12, i32 0, metadata !4, null}
+!27 = metadata !{metadata !28, metadata !29, i64 0}
+!28 = metadata !{metadata !"bar", metadata !29, i64 0, metadata !29, i64 4}
+!29 = metadata !{metadata !"int", metadata !30, i64 0}
+!30 = metadata !{metadata !"omnipotent char", metadata !31, i64 0}
+!31 = metadata !{metadata !"Simple C/C++ TBAA"}
+!32 = metadata !{i32 13, i32 0, metadata !4, null}
+!33 = metadata !{i32 14, i32 0, metadata !4, null}
+!34 = metadata !{i32 18, i32 0, metadata !17, null}
+!35 = metadata !{i32 19, i32 0, metadata !17, null}
+!36 = metadata !{i32 20, i32 0, metadata !17, null}