[DebugInfo] Insert DEBUG_VALUEs after each register redefinition

Summary:
When reinserting debug values after register allocation, make sure to
insert debug values after each redefinition of debug value register in
the slot index range. The reason for this is that DwarfDebug will end
the range of a debug variable when the physical reg is defined. For
instructions with e.g. tied operands this result in prematurely ended
debug range.

This resolves pr34545

Patch by Karl-Johan Karlsson and Bjorn Pettersson

Reviewers: rnk, aprantl

Reviewed By: rnk

Subscribers: bjope, llvm-commits

Differential Revision: https://reviews.llvm.org/D38229

llvm-svn: 314974

2 files changed, 115 insertions, 18 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugVariables.cpp b/llvm/lib/CodeGen/LiveDebugVariables.cpp
index 554a7511ed8..0c81306a9a5 100644
--- a/llvm/lib/CodeGen/LiveDebugVariables.cpp
+++ b/llvm/lib/CodeGen/LiveDebugVariables.cpp
@@ -166,9 +166,11 @@ class UserValue {
   SmallSet<SlotIndex, 2> trimmedDefs;
 
   /// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
-  void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
+  void insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
+                        SlotIndex StopIdx,
                         DbgValueLocation Loc, bool Spilled, LiveIntervals &LIS,
-                        const TargetInstrInfo &TII);
+                        const TargetInstrInfo &TII,
+                        const TargetRegisterInfo &TRI);
 
   /// splitLocation - Replace OldLocNo ranges with NewRegs ranges where NewRegs
   /// is live. Returns true if any changes were made.
@@ -306,7 +308,8 @@ public:
 
   /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
   void emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
-                       const TargetInstrInfo &TRI,
+                       const TargetInstrInfo &TII,
+                       const TargetRegisterInfo &TRI,
                        const BitVector &SpilledLocations);
 
   /// getDebugLoc - Return DebugLoc of this UserValue.
@@ -1055,8 +1058,7 @@ void UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI,
   }
 }
 
-/// findInsertLocation - Find an iterator for inserting a DBG_VALUE
-/// instruction.
+/// Find an iterator for inserting a DBG_VALUE instruction.
 static MachineBasicBlock::iterator
 findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
                    LiveIntervals &LIS) {
@@ -1079,11 +1081,41 @@ findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
                               std::next(MachineBasicBlock::iterator(MI));
 }
 
-void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
+/// Find an iterator for inserting the next DBG_VALUE instruction
+/// (or end if no more insert locations found).
+static MachineBasicBlock::iterator
+findNextInsertLocation(MachineBasicBlock *MBB,
+                       MachineBasicBlock::iterator I,
+                       SlotIndex StopIdx, MachineOperand &LocMO,
+                       LiveIntervals &LIS,
+                       const TargetRegisterInfo &TRI) {
+  if (!LocMO.isReg())
+    return MBB->instr_end();
+  unsigned Reg = LocMO.getReg();
+
+  // Find the next instruction in the MBB that define the register Reg.
+  while (I != MBB->end()) {
+    if (!LIS.isNotInMIMap(*I) &&
+        SlotIndex::isEarlierEqualInstr(StopIdx, LIS.getInstructionIndex(*I)))
+      break;
+    if (I->definesRegister(Reg, &TRI))
+      // The insert location is directly after the instruction/bundle.
+      return std::next(I);
+    ++I;
+  }
+  return MBB->end();
+}
+
+void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
+                                 SlotIndex StopIdx,
                                  DbgValueLocation Loc, bool Spilled,
                                  LiveIntervals &LIS,
-                                 const TargetInstrInfo &TII) {
-  MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
+                                 const TargetInstrInfo &TII,
+                                 const TargetRegisterInfo &TRI) {
+  SlotIndex MBBEndIdx = LIS.getMBBEndIdx(&*MBB);
+  // Only search within the current MBB.
+  StopIdx = (MBBEndIdx < StopIdx) ? MBBEndIdx : StopIdx;
+  MachineBasicBlock::iterator I = findInsertLocation(MBB, StartIdx, LIS);
   MachineOperand &MO = locations[Loc.locNo()];
   ++NumInsertedDebugValues;
 
@@ -1104,18 +1136,25 @@ void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
 
   assert((!Spilled || MO.isFI()) && "a spilled location must be a frame index");
 
-  MachineInstrBuilder MIB =
+  do {
+    MachineInstrBuilder MIB =
       BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
           .add(MO);
-  if (IsIndirect)
-    MIB.addImm(0U);
-  else
-    MIB.addReg(0U, RegState::Debug);
-  MIB.addMetadata(Variable).addMetadata(Expr);
+    if (IsIndirect)
+      MIB.addImm(0U);
+    else
+      MIB.addReg(0U, RegState::Debug);
+    MIB.addMetadata(Variable).addMetadata(Expr);
+
+    // Continue and insert DBG_VALUES after every redefinition of register
+    // associated with the debug value within the range
+    I = findNextInsertLocation(MBB, I, StopIdx, MO, LIS, TRI);
+  } while (I != MBB->end());
 }
 
 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
                                 const TargetInstrInfo &TII,
+                                const TargetRegisterInfo &TRI,
                                 const BitVector &SpilledLocations) {
   MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
 
@@ -1136,17 +1175,17 @@ void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
     SlotIndex MBBEnd = LIS.getMBBEndIdx(&*MBB);
 
     DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
-    insertDebugValue(&*MBB, Start, Loc, Spilled, LIS, TII);
+    insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, LIS, TII, TRI);
     // This interval may span multiple basic blocks.
     // Insert a DBG_VALUE into each one.
-    while(Stop > MBBEnd) {
+    while (Stop > MBBEnd) {
       // Move to the next block.
       Start = MBBEnd;
       if (++MBB == MFEnd)
         break;
       MBBEnd = LIS.getMBBEndIdx(&*MBB);
       DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
-      insertDebugValue(&*MBB, Start, Loc, Spilled, LIS, TII);
+      insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, LIS, TII, TRI);
     }
     DEBUG(dbgs() << '\n');
     if (MBB == MFEnd)
@@ -1165,7 +1204,7 @@ void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
     DEBUG(userValues[i]->print(dbgs(), TRI));
     userValues[i]->rewriteLocations(*VRM, *TRI, SpilledLocations);
-    userValues[i]->emitDebugValues(VRM, *LIS, *TII, SpilledLocations);
+    userValues[i]->emitDebugValues(VRM, *LIS, *TII, *TRI, SpilledLocations);
   }
   EmitDone = true;
 }
diff --git a/llvm/test/DebugInfo/X86/pr34545.ll b/llvm/test/DebugInfo/X86/pr34545.ll
new file mode 100644
index 00000000000..0a97f210107
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/pr34545.ll
@@ -0,0 +1,58 @@
+; RUN: llc -O1 -filetype=asm -mtriple x86_64-unknown-linux-gnu -mcpu=x86-64 -o - %s -stop-after=livedebugvars | FileCheck %s
+
+; CHECK: %eax = MOV32rm
+; CHECK: DBG_VALUE %eax
+; CHECK: %eax = SHL32rCL killed %eax
+; CHECK: DBG_VALUE %eax
+; CHECK: DBG_VALUE %rsp, 0, !{{[0-9]+}}, !DIExpression(DW_OP_constu, 4, DW_OP_minus)
+; CHECK: DBG_VALUE %eax
+; CHECK: %eax = SHL32rCL killed %eax
+; CHECK: DBG_VALUE %eax
+; CHECK: RETQ %eax
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@var = local_unnamed_addr global i32 8, !dbg !0
+@sc = local_unnamed_addr global i32 1, !dbg !6
+
+define i32 @main() local_unnamed_addr !dbg !14 {
+entry:
+  %0 = load i32, i32* @var
+  tail call void @llvm.dbg.value(metadata i32 %0, metadata !18, metadata !DIExpression()), !dbg !20
+  %1 = load i32, i32* @sc
+  %shl = shl i32 %0, %1
+  tail call void @llvm.dbg.value(metadata i32 %shl, metadata !18, metadata !DIExpression()), !dbg !20
+  tail call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"(), !srcloc !25
+  %2 = load i32, i32* @sc
+  %shl2 = shl i32 %shl, %2
+  tail call void @llvm.dbg.value(metadata i32 %shl2, metadata !18, metadata !DIExpression()), !dbg !20
+  store i32 %shl2, i32* @var
+  ret i32 %shl2
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!10, !11, !12}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "var", scope: !2, file: !3, line: 10, type: !9, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "bar.c", directory: ".")
+!4 = !{}
+!5 = !{!0, !6}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "sc", scope: !2, file: !3, line: 11, type: !8, isLocal: false, isDefinition: true)
+!8 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !{i32 2, !"Dwarf Version", i32 4}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!14 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 12, type: !15, isLocal: false, isDefinition: true, scopeLine: 12, isOptimized: true, unit: !2, variables: !17)
+!15 = !DISubroutineType(types: !16)
+!16 = !{!9}
+!17 = !{!18}
+!18 = !DILocalVariable(name: "bazinga", scope: !14, file: !3, line: 13, type: !9)
+!20 = !DILocation(line: 13, column: 7, scope: !14)
+!25 = !{i32 -2147471481}