[MachineDebugify] Insert synthetic DBG_VALUE instructions

[vsk]

Summary

Teach MachineDebugify how to insert DBG_VALUE instructions. This can
help find bugs causing CodeGen differences when debug info is present.
DBG_VALUE instructions are only emitted when -debugify-level is set to
locations+variables.

There is essentially no attempt made to match up DBG_VALUE register
operands with the local variables they ought to correspond to. I'm not
sure how to improve the situation. In some cases (MachineMemOperand?)
it's possible to find the IR instruction a MachineInstr corresponds to,
but in general this seems to call for "undoing" the work done by ISel.

[vsk]

Do not insert DBG_VALUEs after phis, this is illegal. Test coverage for this comes from legalize-phi-insertpt-decrement.mir.

[dsanders]

There is essentially no attempt made to match up DBG_VALUE register
operands with the local variables they ought to correspond to. I'm not
sure how to improve the situation.

Yeah, and it gets harder the further down the pipeline you go. Especially since the pipeline is fairly free form and even early passes are allowed to select target instructions. I don't think it really matters too much if the IR-level dbg.value maps to the 'correct' MIR-level vreg as we're really looking for places the DBG_VALUE causes crashes or causes CodeGen changes. Eventually we might expand into checking that DBG_VALUE's are handled as opposed to accidentally lost. Even then though we're more concerned with preserving MIR level information rather than the actual mapping to IR-level

llvm/lib/CodeGen/MachineDebugify.cpp

55–64

I notice that this only generates enough information to cover the line numbers in the IR-level. That limits the vregs covered by DBG_VALUE's to the first few as there's typically more MIR instructions than IR instructions. Is it possible to cover more of the MIR vregs?

llvm/test/CodeGen/Generic/MIRDebugify/locations-and-values.mir

1

We ought to rename this test if it's going to cover the DBG_VALUE case too

[vsk]

Cover each non-phi reg def with a DBG_VALUE, per Daniel's suggestion.

I thought I fixed the last CodeGen-difference-with-debug bug in the AArch64 backend with D78157, but with this change, I've found a few more :).

[paquette]

llvm/lib/CodeGen/MachineDebugify.cpp

59–62

Maybe a bit nicer:

if (Line2Var.empty())
  continue;

for (MachineOperand &MO : MI.operands())
  ...

[vsk]

Early-exit in loop

[vsk]

One more (and I think the last!) update to the testing strategy.

Instead of limiting -mir-debugify to inserting DBG_VALUEs after register
definitions, have it insert DBG_VALUEs after /every/ real instruction. When a
register def isn't available, just describe a constant.

Also, sometimes MIR tests are written with skeletal (or no) IR. We still want
-mir-debugify test coverage in these cases, so force the IR debugify pass to
describe at least one variable per function.

This uncovers a few more CodeGen-difference-with-debug issues.

[dsanders]

LGTM

[thakis]

Looks like the tests added here fail:
http://lab.llvm.org:8011/#/builders/109/builds/4730
http://45.33.8.238/linux/35299/step_12.txt

Since the tree is in pretty bad shape right now (this is at least the 3rd consecutive breakage), I'm reverting this.

[thakis]

Sorry, I somehow thought this landed an hour ago, not many months. Will reland, apologies :/

llvm/lib/CodeGen/MachineDebugify.cpp

 //===- MachineDebugify.cpp - Attach synthetic debug info to everything ----===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file This pass attaches synthetic debug info to everything. It can be used
-/// to create targeted tests for debug info preservation.
+/// to create targeted tests for debug info preservation, or test for CodeGen
+/// differences with vs. without debug info.
 ///
 /// This isn't intended to have feature parity with Debugify.
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/DebugInfo.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Transforms/Utils/Debugify.h"
 
 #define DEBUG_TYPE "mir-debugify"
 
 using namespace llvm;
 
 namespace {
 bool applyDebugifyMetadataToMachineFunction(MachineModuleInfo &MMI,
                                             DIBuilder &DIB, Function &F) {
   MachineFunction *MaybeMF = MMI.getMachineFunction(F);
   if (!MaybeMF)
     return false;
   MachineFunction &MF = *MaybeMF;
+  const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
 
   DISubprogram *SP = F.getSubprogram();
   assert(SP && "IR Debugify just created it?");
 
-  LLVMContext &Ctx = F.getParent()->getContext();
-  unsigned NextLine = SP->getLine();
+  Module &M = *F.getParent();
+  LLVMContext &Ctx = M.getContext();
 
+  unsigned NextLine = SP->getLine();
   for (MachineBasicBlock &MBB : MF) {
     for (MachineInstr &MI : MBB) {
       // This will likely emit line numbers beyond the end of the imagined
       // source function and into subsequent ones. We don't do anything about
       // that as it doesn't really matter to the compiler where the line is in
       // the imaginary source code.
       MI.setDebugLoc(DILocation::get(Ctx, NextLine++, 1, SP));
     }
   }
 
+  // Find local variables defined by debugify. No attempt is made to match up
+  // MIR-level regs to the 'correct' IR-level variables: there isn't a simple
+  // way to do that, and it isn't necessary to find interesting CodeGen bugs.
+  // Instead, simply keep track of one variable per line. Later, we can insert
+  // DBG_VALUE insts that point to these local variables. Emitting DBG_VALUEs
+  // which cover a wide range of lines can help stress the debug info passes:
+  // if we can't do that, fall back to using the local variable which precedes
+  // all the others.
+  Function *DbgValF = M.getFunction("llvm.dbg.value");
+  DbgValueInst *EarliestDVI = nullptr;
+  DenseMap<unsigned, DILocalVariable *> Line2Var;
+  DIExpression *Expr = nullptr;
+  if (DbgValF) {
+    for (const Use &U : DbgValF->uses()) {
+      auto *DVI = dyn_cast<DbgValueInst>(U.getUser());
+      if (!DVI || DVI->getFunction() != &F)
+        continue;
+      unsigned Line = DVI->getDebugLoc().getLine();
+      assert(Line != 0 && "debugify should not insert line 0 locations");
+      Line2Var[Line] = DVI->getVariable();
+      if (!EarliestDVI || Line < EarliestDVI->getDebugLoc().getLine())
+        EarliestDVI = DVI;
+      Expr = DVI->getExpression();
+    }
+  }
+  if (Line2Var.empty())
+    return true;
+
+  // Now, try to insert a DBG_VALUE instruction after each real instruction.
+  // Do this by introducing debug uses of each register definition. If that is
+  // not possible (e.g. we have a phi or a meta instruction), emit a constant.
+  uint64_t NextImm = 0;
+  const MCInstrDesc &DbgValDesc = TII.get(TargetOpcode::DBG_VALUE);
+  for (MachineBasicBlock &MBB : MF) {
+    MachineBasicBlock::iterator FirstNonPHIIt = MBB.getFirstNonPHI();
+    for (auto I = MBB.begin(), E = MBB.end(); I != E; ) {
+      MachineInstr &MI = *I;
+      ++I;
+
+      // `I` may point to a DBG_VALUE created in the previous loop iteration.
+      if (MI.isDebugInstr())
+        continue;
+
+      // It's not allowed to insert DBG_VALUEs after a terminator.
+      if (MI.isTerminator())
+        continue;
+
+      // Find a suitable insertion point for the DBG_VALUE.
+      auto InsertBeforeIt = MI.isPHI() ? FirstNonPHIIt : I;
+
+      // Find a suitable local variable for the DBG_VALUE.
+      unsigned Line = MI.getDebugLoc().getLine();
+      if (!Line2Var.count(Line))
+        Line = EarliestDVI->getDebugLoc().getLine();
+      DILocalVariable *LocalVar = Line2Var[Line];
+      assert(LocalVar && "No variable for current line?");
+
+      // Emit DBG_VALUEs for register definitions.
+      SmallVector<MachineOperand *, 4> RegDefs;
+      for (MachineOperand &MO : MI.operands())
+        if (MO.isReg() && MO.isDef() && MO.getReg())
+          RegDefs.push_back(&MO);
+      for (MachineOperand *MO : RegDefs)
+        BuildMI(MBB, InsertBeforeIt, MI.getDebugLoc(), DbgValDesc,
+                /*IsIndirect=*/false, *MO, LocalVar, Expr);
+
+      // OK, failing that, emit a constant DBG_VALUE.
+      if (RegDefs.empty()) {
+        auto ImmOp = MachineOperand::CreateImm(NextImm++);
+        BuildMI(MBB, InsertBeforeIt, MI.getDebugLoc(), DbgValDesc,
+                /*IsIndirect=*/false, ImmOp, LocalVar, Expr);
+      }
+    }
+  }
+
   return true;
 }
 
 /// ModulePass for attaching synthetic debug info to everything, used with the
 /// legacy module pass manager.
 struct DebugifyMachineModule : public ModulePass {
   bool runOnModule(Module &M) override {
     MachineModuleInfo &MMI =

llvm/lib/Transforms/Utils/Debugify.cpp

bool llvm::applyDebugifyMetadata(
   // Skip modules with debug info.
   if (M.getNamedMetadata("llvm.dbg.cu")) {
     dbg() << Banner << "Skipping module with debug info\n";
     return false;
   }
 
   DIBuilder DIB(M);
   LLVMContext &Ctx = M.getContext();
+  auto *Int32Ty = Type::getInt32Ty(Ctx);
 
   // Get a DIType which corresponds to Ty.
   DenseMap<uint64_t, DIType *> TypeCache;
   auto getCachedDIType = [&](Type *Ty) -> DIType * {
     uint64_t Size = getAllocSizeInBits(M, Ty);
     DIType *&DTy = TypeCache[Size];
     if (!DTy) {
       std::string Name = "ty" + utostr(Size);
       DTy = DIB.createBasicType(Name, Size, dwarf::DW_ATE_unsigned);
     }
     return DTy;
   };
 
   unsigned NextLine = 1;
   unsigned NextVar = 1;
   auto File = DIB.createFile(M.getName(), "/");
   auto CU = DIB.createCompileUnit(dwarf::DW_LANG_C, File, "debugify",
                                   /*isOptimized=*/true, "", 0);
 
   // Visit each instruction.
   for (Function &F : Functions) {
     if (isFunctionSkipped(F))
       continue;
 
+    bool InsertedDbgVal = false;
     auto SPType = DIB.createSubroutineType(DIB.getOrCreateTypeArray(None));
     DISubprogram::DISPFlags SPFlags =
         DISubprogram::SPFlagDefinition | DISubprogram::SPFlagOptimized;
     if (F.hasPrivateLinkage() || F.hasInternalLinkage())
       SPFlags |= DISubprogram::SPFlagLocalToUnit;
     auto SP = DIB.createFunction(CU, F.getName(), F.getName(), File, NextLine,
                                  SPType, NextLine, DINode::FlagZero, SPFlags);
     F.setSubprogram(SP);
+
+    // Helper that inserts a dbg.value before \p InsertBefore, copying the
+    // location (and possibly the type, if it's non-void) from \p TemplateInst.
+    auto insertDbgVal = [&](Instruction &TemplateInst,
+                            Instruction *InsertBefore) {
+      std::string Name = utostr(NextVar++);
+      Value *V = &TemplateInst;
+      if (TemplateInst.getType()->isVoidTy())
+        V = ConstantInt::get(Int32Ty, 0);
+      const DILocation *Loc = TemplateInst.getDebugLoc().get();
+      auto LocalVar = DIB.createAutoVariable(SP, Name, File, Loc->getLine(),
+                                             getCachedDIType(V->getType()),
+                                             /*AlwaysPreserve=*/true);
+      DIB.insertDbgValueIntrinsic(V, LocalVar, DIB.createExpression(), Loc,
+                                  InsertBefore);
+    };
+
     for (BasicBlock &BB : F) {
       // Attach debug locations.
       for (Instruction &I : BB)
         I.setDebugLoc(DILocation::get(Ctx, NextLine++, 1, SP));
 
       if (DebugifyLevel < Level::LocationsAndVariables)
         continue;
 
for (BasicBlock &BB : F) {
         if (I->getType()->isVoidTy())
           continue;
 
         // Phis and EH pads must be grouped at the beginning of the block.
         // Only advance the insertion point when we finish visiting these.
         if (!isa<PHINode>(I) && !I->isEHPad())
           InsertBefore = I->getNextNode();
 
-        std::string Name = utostr(NextVar++);
-        const DILocation *Loc = I->getDebugLoc().get();
-        auto LocalVar = DIB.createAutoVariable(SP, Name, File, Loc->getLine(),
-                                               getCachedDIType(I->getType()),
-                                               /*AlwaysPreserve=*/true);
-        DIB.insertDbgValueIntrinsic(I, LocalVar, DIB.createExpression(), Loc,
-                                    InsertBefore);
-      }
+        insertDbgVal(*I, InsertBefore);
+        InsertedDbgVal = true;
+      }
+    // Make sure we emit at least one dbg.value, otherwise MachineDebugify may
+    // not have anything to work with as it goes about inserting DBG_VALUEs.
+    // (It's common for MIR tests to be written containing skeletal IR with
+    // empty functions -- we're still interested in debugifying the MIR within
+    // those tests, and this helps with that.)
+    if (DebugifyLevel == Level::LocationsAndVariables && !InsertedDbgVal) {
+      auto *Term = findTerminatingInstruction(F.getEntryBlock());
+      insertDbgVal(*Term, Term);
     }
     if (ApplyToMF)
       ApplyToMF(DIB, F);
     DIB.finalizeSubprogram(SP);
   }
   DIB.finalize();
 
   // Track the number of distinct lines and variables.
   NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.debugify");
-  auto *IntTy = Type::getInt32Ty(Ctx);
   auto addDebugifyOperand = [&](unsigned N) {
     NMD->addOperand(MDNode::get(
-        Ctx, ValueAsMetadata::getConstant(ConstantInt::get(IntTy, N))));
+        Ctx, ValueAsMetadata::getConstant(ConstantInt::get(Int32Ty, N))));
   };
   addDebugifyOperand(NextLine - 1); // Original number of lines.
   addDebugifyOperand(NextVar - 1);  // Original number of variables.
   assert(NMD->getNumOperands() == 2 &&
          "llvm.debugify should have exactly 2 operands!");
 
   // Claim that this synthetic debug info is valid.
   StringRef DIVersionKey = "Debug Info Version";

llvm/test/CodeGen/AArch64/GlobalISel/constant-mir-debugify.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -debugify-and-strip-all-safe=0 -run-pass=mir-debugify -verify-machineinstrs -mtriple aarch64-unknown-unknown %s -o - | FileCheck %s
+...
+---
+name:            fconstant_to_constant_s32
+alignment:       4
+tracksRegLiveness: true
+frameInfo:
+  maxAlignment:    1
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    liveins: $x0
+    ; CHECK-LABEL: name: fconstant_to_constant_s32
+    ; CHECK: liveins: $x0
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x0, debug-location !10
+    ; CHECK: DBG_VALUE [[COPY]](p0), $noreg, !8, !DIExpression(), debug-location !10
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_FCONSTANT float 0x3FA99999A0000000, debug-location !DILocation(line: 2, column: 1, scope: !5)
+    ; CHECK: DBG_VALUE [[C]](s32), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 2, column: 1, scope: !5)
+    ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 524, debug-location !DILocation(line: 3, column: 1, scope: !5)
+    ; CHECK: DBG_VALUE [[C1]](s64), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 3, column: 1, scope: !5)
+    ; CHECK: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C1]](s64), debug-location !DILocation(line: 4, column: 1, scope: !5)
+    ; CHECK: DBG_VALUE [[PTR_ADD]](p0), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 4, column: 1, scope: !5)
+    ; CHECK: G_STORE [[C]](s32), [[PTR_ADD]](p0), debug-location !DILocation(line: 5, column: 1, scope: !5) :: (store 4)
+    ; CHECK: DBG_VALUE 0, $noreg, !8, !DIExpression(), debug-location !DILocation(line: 5, column: 1, scope: !5)
+    ; CHECK: RET_ReallyLR debug-location !DILocation(line: 6, column: 1, scope: !5)
+    %0:_(p0) = COPY $x0
+    %3:_(s32) = G_FCONSTANT float 0x3FA99999A0000000
+    %1:_(s64) = G_CONSTANT i64 524
+    %2:_(p0) = G_PTR_ADD %0, %1(s64)
+    G_STORE %3(s32), %2(p0) :: (store 4)
+    RET_ReallyLR
+...

llvm/test/CodeGen/AArch64/GlobalISel/legalize-phi-insertpt-decrement.mir

 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
-# RUN: llc -O0 -mtriple=aarch64-unknown-unknown -verify-machineinstrs -run-pass=legalizer %s -o - | FileCheck %s
+# RUN: llc -debugify-and-strip-all-safe -O0 -mtriple=aarch64-unknown-unknown -verify-machineinstrs -run-pass=legalizer %s -o - | FileCheck %s
 --- |
   target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 
   define void @snork() {
   bb:
     br label %bb1
 
   bb1:                                              ; preds = %bb3, %bb

llvm/test/CodeGen/AArch64/GlobalISel/phi-mir-debugify.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -debugify-and-strip-all-safe=0 -run-pass=mir-debugify -verify-machineinstrs %s -o - | FileCheck %s
+--- |
+  target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+  target triple = "aarch64-unknown-unknown"
+
+  define i32 @legalize_phi(i32 %argc) {
+  entry:
+    ret i32 0
+  }
+
+...
+---
+name:            legalize_phi
+alignment:       4
+exposesReturnsTwice: false
+legalized:       false
+regBankSelected: false
+selected:        false
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: _, preferred-register: '' }
+  - { id: 1, class: _, preferred-register: '' }
+  - { id: 2, class: _, preferred-register: '' }
+  - { id: 3, class: _, preferred-register: '' }
+  - { id: 4, class: _, preferred-register: '' }
+  - { id: 5, class: _, preferred-register: '' }
+  - { id: 6, class: _, preferred-register: '' }
+  - { id: 7, class: _, preferred-register: '' }
+  - { id: 8, class: _, preferred-register: '' }
+  - { id: 9, class: _, preferred-register: '' }
+  - { id: 10, class: _, preferred-register: '' }
+liveins:
+body:             |
+  ; CHECK-LABEL: name: legalize_phi
+  ; CHECK: bb.0:
+  ; CHECK:   successors: %bb.1(0x40000000), %bb.2(0x40000000)
+  ; CHECK:   liveins: $w0
+  ; CHECK:   [[COPY:%[0-9]+]]:_(s32) = COPY $w0, debug-location !10
+  ; CHECK:   DBG_VALUE [[COPY]](s32), $noreg, !8, !DIExpression(), debug-location !10
+  ; CHECK:   [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0, debug-location !DILocation(line: 2, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[C]](s32), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 2, column: 1, scope: !5)
+  ; CHECK:   [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 1, debug-location !DILocation(line: 3, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[C1]](s32), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 3, column: 1, scope: !5)
+  ; CHECK:   [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 2, debug-location !DILocation(line: 4, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[C2]](s32), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 4, column: 1, scope: !5)
+  ; CHECK:   [[ICMP:%[0-9]+]]:_(s1) = G_ICMP intpred(ugt), [[COPY]](s32), [[C]], debug-location !DILocation(line: 5, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[ICMP]](s1), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 5, column: 1, scope: !5)
+  ; CHECK:   G_BRCOND [[ICMP]](s1), %bb.1, debug-location !DILocation(line: 6, column: 1, scope: !5)
+  ; CHECK:   G_BR %bb.2, debug-location !DILocation(line: 7, column: 1, scope: !5)
+  ; CHECK: bb.1:
+  ; CHECK:   successors: %bb.3(0x80000000)
+  ; CHECK:   [[ADD:%[0-9]+]]:_(s32) = G_ADD [[COPY]], [[C1]], debug-location !DILocation(line: 8, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[ADD]](s32), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 8, column: 1, scope: !5)
+  ; CHECK:   [[TRUNC:%[0-9]+]]:_(s1) = G_TRUNC [[ADD]](s32), debug-location !DILocation(line: 9, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[TRUNC]](s1), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 9, column: 1, scope: !5)
+  ; CHECK:   G_BR %bb.3, debug-location !DILocation(line: 10, column: 1, scope: !5)
+  ; CHECK: bb.2:
+  ; CHECK:   successors: %bb.3(0x80000000)
+  ; CHECK:   [[ADD1:%[0-9]+]]:_(s32) = G_ADD [[COPY]], [[C2]], debug-location !DILocation(line: 11, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[ADD1]](s32), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 11, column: 1, scope: !5)
+  ; CHECK:   [[TRUNC1:%[0-9]+]]:_(s1) = G_TRUNC [[ADD1]](s32), debug-location !DILocation(line: 12, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[TRUNC1]](s1), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 12, column: 1, scope: !5)
+  ; CHECK: bb.3:
+  ; CHECK:   [[PHI:%[0-9]+]]:_(s1) = G_PHI [[TRUNC]](s1), %bb.1, [[TRUNC1]](s1), %bb.2, debug-location !DILocation(line: 13, column: 1, scope: !5)
+  ; CHECK:   [[PHI1:%[0-9]+]]:_(s1) = G_PHI [[TRUNC]](s1), %bb.1, [[TRUNC1]](s1), %bb.2, debug-location !DILocation(line: 14, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[PHI]](s1), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 13, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[PHI1]](s1), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 14, column: 1, scope: !5)
+  ; CHECK:   [[ZEXT:%[0-9]+]]:_(s32) = G_ZEXT [[PHI]](s1), debug-location !DILocation(line: 15, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE [[ZEXT]](s32), $noreg, !8, !DIExpression(), debug-location !DILocation(line: 15, column: 1, scope: !5)
+  ; CHECK:   $w0 = COPY [[ZEXT]](s32), debug-location !DILocation(line: 16, column: 1, scope: !5)
+  ; CHECK:   DBG_VALUE $w0, $noreg, !8, !DIExpression(), debug-location !DILocation(line: 16, column: 1, scope: !5)
+  ; CHECK:   RET_ReallyLR implicit $w0, debug-location !DILocation(line: 17, column: 1, scope: !5)
+  bb.0:
+    successors: %bb.1(0x40000000), %bb.2(0x40000000)
+    liveins: $w0
+
+    %0(s32) = COPY $w0
+    %1(s32) = G_CONSTANT i32 0
+    %3(s32) = G_CONSTANT i32 1
+    %6(s32) = G_CONSTANT i32 2
+    %2(s1) = G_ICMP intpred(ugt), %0(s32), %1
+    G_BRCOND %2(s1), %bb.1
+    G_BR %bb.2
+
+  bb.1:
+    successors: %bb.3(0x80000000)
+
+    %4(s32) = G_ADD %0, %3
+    %5(s1) = G_TRUNC %4(s32)
+    G_BR %bb.3
+
+  bb.2:
+    successors: %bb.3(0x80000000)
+
+    %7(s32) = G_ADD %0, %6
+    %8(s1) = G_TRUNC %7(s32)
+
+  bb.3:
+    %9(s1) = G_PHI %5(s1), %bb.1, %8(s1), %bb.2
+    %11:_(s1) = G_PHI %5(s1), %bb.1, %8(s1), %bb.2
+    %10(s32) = G_ZEXT %9(s1)
+    $w0 = COPY %10(s32)
+    RET_ReallyLR implicit $w0
+
+...

llvm/test/CodeGen/Generic/MIRDebugify/locations-and-values.mir

 # RUN: llc -run-pass=mir-debugify -o - %s | FileCheck --check-prefixes=ALL,VALUE %s
 # RUN: llc -run-pass=mir-debugify -debugify-level=locations -o - %s | FileCheck --check-prefixes=ALL --implicit-check-not=dbg.value %s
 # RUN: llc -run-pass=mir-debugify,mir-strip-debug,mir-debugify -o - %s | FileCheck --check-prefixes=ALL,VALUE %s
 --- |
   ; ModuleID = 'loc-only.ll'
   source_filename = "loc-only.ll"
   
   ; ALL-LABEL: @test
   define i32 @test(i32 %a, i32 %b) {
     %add = add i32 %a, 2
   ; ALL-NEXT:  %add = add i32 %a, 2, !dbg [[L1:![0-9]+]]
   ; VALUE-NEXT: call void @llvm.dbg.value(metadata i32 %add, metadata [[add:![0-9]+]], metadata !DIExpression()), !dbg [[L1]]
     %sub = sub i32 %add, %b
   ; ALL-NEXT: %sub = sub i32 %add, %b, !dbg [[L2:![0-9]+]]
   ; VALUE-NEXT: call void @llvm.dbg.value(metadata i32 %sub, metadata [[sub:![0-9]+]], metadata !DIExpression()), !dbg [[L2]]
   ; ALL-NEXT: ret i32 %sub, !dbg [[L3:![0-9]+]]
     ret i32 %sub
   }
 
-  ; CHECK: !llvm.dbg.cu = !{!0}
-  ; CHECK: !llvm.debugify =
-  ; CHECK: !llvm.module.flags = !{![[VERSION:[0-9]+]]}
-  ; CHECK: !0 = distinct !DICompileUnit(
-  ; CHECK: ![[VERSION]] = !{i32 2, !"Debug Info Version", i32 3}
+  ; ALL: !llvm.dbg.cu = !{!0}
+  ; ALL: !llvm.debugify =
+  ; ALL: !llvm.module.flags = !{![[VERSION:[0-9]+]]}
+  ; ALL: !0 = distinct !DICompileUnit(
+  ; ALL: ![[VERSION]] = !{i32 2, !"Debug Info Version", i32 3}
+  ; VALUE: [[VAR1:![0-9]+]] = !DILocalVariable(name: "1"
+  ; VALUE: [[VAR2:![0-9]+]] = !DILocalVariable(name: "2"
 
 ...
 ---
 name:            test
 body:             |
   bb.1 (%ir-block.0):
     %0:_(s32) = IMPLICIT_DEF
     %1:_(s32) = IMPLICIT_DEF
     %2:_(s32) = G_CONSTANT i32 2
     %3:_(s32) = G_ADD %0, %2
     %4:_(s32) = G_SUB %3, %1
     ; There's no attempt to have the locations make sense as it's an imaginary
     ; source file anyway. These first three coincide with IR-level information
     ; and therefore use metadata references.
     ; ALL: %0:_(s32) = IMPLICIT_DEF debug-location [[L1]]
+    ; VALUE: DBG_VALUE %0(s32), $noreg, [[VAR1]], !DIExpression(), debug-location [[L1]]
     ; ALL: %1:_(s32) = IMPLICIT_DEF debug-location [[L2]]
+    ; VALUE: DBG_VALUE %1(s32), $noreg, [[VAR2]], !DIExpression(), debug-location [[L2]]
     ; ALL: %2:_(s32) = G_CONSTANT i32 2, debug-location [[L3]]
+    ; VALUE: DBG_VALUE %2(s32), $noreg, [[VAR1]], !DIExpression(), debug-location [[L3]]
     ; ALL: %3:_(s32) = G_ADD %0, %2, debug-location !DILocation(line: 4, column: 1, scope: !6)
+    ; VALUE: DBG_VALUE %3(s32), $noreg, [[VAR1]], !DIExpression(), debug-location !DILocation(line: 4
     ; ALL: %4:_(s32) = G_SUB %3, %1, debug-location !DILocation(line: 5, column: 1, scope: !6)
+    ; VALUE: DBG_VALUE %4(s32), $noreg, [[VAR1]], !DIExpression(), debug-location !DILocation(line: 5
 ...

llvm/test/DebugInfo/debugify.ll

 ; CHECK-DAG: ![[CALL1]] = !DILocation(line: 2, column: 1
 ; CHECK-DAG: ![[ADD1]] = !DILocation(line: 3, column: 1
 ; CHECK-DAG: ![[RET2]] = !DILocation(line: 4, column: 1
 ; CHECK-DAG: ![[musttail]] = !DILocation(line: 5, column: 1
 ; CHECK-DAG: ![[musttailRes]] = !DILocation(line: 6, column: 1
 
 ; --- DILocalVariables
 ; CHECK-DAG: ![[TY32:.*]] = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
-; CHECK-DAG: !DILocalVariable(name: "1", scope: {{.*}}, file: {{.*}}, line: 3, type: ![[TY32]])
+; CHECK-DAG: !DILocalVariable(name: "1", scope: {{.*}}, file: {{.*}}, line: 1, type: ![[TY32]])
+; CHECK-DAG: !DILocalVariable(name: "2", scope: {{.*}}, file: {{.*}}, line: 3, type: ![[TY32]])
+; CHECK-DAG: !DILocalVariable(name: "3", scope: {{.*}}, file: {{.*}}, line: 5, type: ![[TY32]])
 
 ; --- Metadata counts
 ; CHECK-DAG: ![[NUM_INSTS]] = !{i32 6}
-; CHECK-DAG: ![[NUM_VARS]] = !{i32 1}
+; CHECK-DAG: ![[NUM_VARS]] = !{i32 3}
 
 ; --- Repeat case
 ; CHECK-REPEAT: ModuleDebugify: Skipping module with debug info
 
 ; --- Failure case
 ; CHECK-FAIL: ERROR: Instruction with empty DebugLoc in function foo --   ret void
 ; CHECK-FAIL: ERROR: Instruction with empty DebugLoc in function bar --   call void @foo()
 ; CHECK-FAIL: ERROR: Instruction with empty DebugLoc in function bar --   {{.*}} add i32 0, 1