[DebugInfo][RemoveDIs] Handle non-instr debug-info in GlobalISel (#75228)

The RemoveDIs project is aiming to eliminate debug intrinsics like
dbg.value and dbg.declare from LLVM, and replace them with DPValue objects
attached to instructions. ISel is one of the "terminals" where that
information needs to be converted into MIR format: this patch implements
support for that in GlobalISel. We aim for the output of LLVM to be
identical with/without RemoveDIs debug-info.

This patch should be NFC, as we're handling the same data about variables
stored in a different format -- it now appears in a DPValue object rather
than as an intrinsic. To that end, I've refactored the handling of
dbg.values into a dedicated function, and call it whenever a dbg.value or a
DPValue is encountered. dbg.declare is handled in a similar way.

Testing: adding the --try-experimental-debuginfo-iterators switch to llc
causes it to try and convert to the "new" debug-info format if it's built
in (LLVM_EXPERIMENTAL_DEBUGINFO_ITERATORS=On), and it'll be covered by our
buildbot. One test has a few extra wildcard-regexes added: this is because
there's some extra data printed about attached debug-info, which is safe to
ignore.

Author: jmorse

llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h

@@ -204,6 +204,27 @@ class IRTranslator : public MachineFunctionPass {
   /// \return true if the materialization succeeded.
   bool translate(const Constant &C, Register Reg);
 
+  /// Examine any debug-info attached to the instruction (in the form of
+  /// DPValues) and translate it.
+  void translateDbgInfo(const Instruction &Inst,
+                          MachineIRBuilder &MIRBuilder);
+
+  /// Translate a debug-info record of a dbg.value into a DBG_* instruction.
+  /// Pass in all the contents of the record, rather than relying on how it's
+  /// stored.
+  void translateDbgValueRecord(Value *V, bool HasArgList,
+                         const DILocalVariable *Variable,
+                         const DIExpression *Expression, const DebugLoc &DL,
+                         MachineIRBuilder &MIRBuilder);
+
+  /// Translate a debug-info record of a dbg.declare into an indirect DBG_*
+  /// instruction. Pass in all the contents of the record, rather than relying
+  /// on how it's stored.
+  void translateDbgDeclareRecord(Value *Address, bool HasArgList,
+                         const DILocalVariable *Variable,
+                         const DIExpression *Expression, const DebugLoc &DL,
+                         MachineIRBuilder &MIRBuilder);
+
   // Translate U as a copy of V.
   bool translateCopy(const User &U, const Value &V,
                      MachineIRBuilder &MIRBuilder);
@@ -250,14 +271,14 @@ class IRTranslator : public MachineFunctionPass {
   /// possible.
   std::optional<MCRegister> getArgPhysReg(Argument &Arg);
 
-  /// If DebugInst targets an Argument and its expression is an EntryValue,
-  /// lower it as an entry in the MF debug table.
-  bool translateIfEntryValueArgument(const DbgDeclareInst &DebugInst);
-
-  /// If DebugInst targets an Argument and its expression is an EntryValue,
-  /// lower as a DBG_VALUE targeting the corresponding livein register for that
-  /// Argument.
-  bool translateIfEntryValueArgument(const DbgValueInst &DebugInst,
+  /// If debug-info targets an Argument and its expression is an EntryValue,
+  /// lower it as either an entry in the MF debug table (dbg.declare), or a
+  /// DBG_VALUE targeting the corresponding livein register for that Argument
+  /// (dbg.value).
+  bool translateIfEntryValueArgument(bool isDeclare, Value *Arg,
+                                     const DILocalVariable *Var,
+                                     const DIExpression *Expr,
+                                     const DebugLoc &DL,
                                      MachineIRBuilder &MIRBuilder);
 
   bool translateInlineAsm(const CallBase &CB, MachineIRBuilder &MIRBuilder);

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -162,7 +162,8 @@ class DILocationVerifier : public GISelChangeObserver {
     // they could have originated from constants, and we don't want a jumpy
     // debug experience.
     assert((CurrInst->getDebugLoc() == MI.getDebugLoc() ||
-            (MI.getParent()->isEntryBlock() && !MI.getDebugLoc())) &&
+            (MI.getParent()->isEntryBlock() && !MI.getDebugLoc()) ||
+            (MI.isDebugInstr())) &&
            "Line info was not transferred to all instructions");
   }
 };
@@ -2006,47 +2007,35 @@ std::optional<MCRegister> IRTranslator::getArgPhysReg(Argument &Arg) {
   return VRegDef->getOperand(1).getReg().asMCReg();
 }
 
-bool IRTranslator::translateIfEntryValueArgument(const DbgValueInst &DebugInst,
+bool IRTranslator::translateIfEntryValueArgument(bool isDeclare, Value *Val,
+                                                 const DILocalVariable *Var,
+                                                 const DIExpression *Expr,
+                                                 const DebugLoc &DL,
                                                  MachineIRBuilder &MIRBuilder) {
-  auto *Arg = dyn_cast<Argument>(DebugInst.getValue());
+  auto *Arg = dyn_cast<Argument>(Val);
   if (!Arg)
     return false;
 
-  const DIExpression *Expr = DebugInst.getExpression();
   if (!Expr->isEntryValue())
     return false;
 
   std::optional<MCRegister> PhysReg = getArgPhysReg(*Arg);
   if (!PhysReg) {
-    LLVM_DEBUG(dbgs() << "Dropping dbg.value: expression is entry_value but "
-                         "couldn't find a physical register\n"
-                      << DebugInst << "\n");
+    LLVM_DEBUG(dbgs() << "Dropping dbg." << (isDeclare ? "declare" : "value")
+                      << ": expression is entry_value but "
+                      << "couldn't find a physical register\n");
+    LLVM_DEBUG(dbgs() << *Var << "\n");
     return true;
   }
 
-  MIRBuilder.buildDirectDbgValue(*PhysReg, DebugInst.getVariable(),
-                                 DebugInst.getExpression());
-  return true;
-}
-
-bool IRTranslator::translateIfEntryValueArgument(
-    const DbgDeclareInst &DebugInst) {
-  auto *Arg = dyn_cast<Argument>(DebugInst.getAddress());
-  if (!Arg)
-    return false;
-
-  const DIExpression *Expr = DebugInst.getExpression();
-  if (!Expr->isEntryValue())
-    return false;
-
-  std::optional<MCRegister> PhysReg = getArgPhysReg(*Arg);
-  if (!PhysReg)
-    return false;
+  if (isDeclare) {
+    // Append an op deref to account for the fact that this is a dbg_declare.
+    Expr = DIExpression::append(Expr, dwarf::DW_OP_deref);
+    MF->setVariableDbgInfo(Var, Expr, *PhysReg, DL);
+  } else {
+    MIRBuilder.buildDirectDbgValue(*PhysReg, Var, Expr);
+  }
 
-  // Append an op deref to account for the fact that this is a dbg_declare.
-  Expr = DIExpression::append(Expr, dwarf::DW_OP_deref);
-  MF->setVariableDbgInfo(DebugInst.getVariable(), Expr, *PhysReg,
-                         DebugInst.getDebugLoc());
   return true;
 }
 
@@ -2100,32 +2089,8 @@ bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
   case Intrinsic::dbg_declare: {
     const DbgDeclareInst &DI = cast<DbgDeclareInst>(CI);
     assert(DI.getVariable() && "Missing variable");
-
-    const Value *Address = DI.getAddress();
-    if (!Address || isa<UndefValue>(Address)) {
-      LLVM_DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
-      return true;
-    }
-
-    assert(DI.getVariable()->isValidLocationForIntrinsic(
-               MIRBuilder.getDebugLoc()) &&
-           "Expected inlined-at fields to agree");
-    auto AI = dyn_cast<AllocaInst>(Address);
-    if (AI && AI->isStaticAlloca()) {
-      // Static allocas are tracked at the MF level, no need for DBG_VALUE
-      // instructions (in fact, they get ignored if they *do* exist).
-      MF->setVariableDbgInfo(DI.getVariable(), DI.getExpression(),
-                             getOrCreateFrameIndex(*AI), DI.getDebugLoc());
-      return true;
-    }
-
-    if (translateIfEntryValueArgument(DI))
-      return true;
-
-    // A dbg.declare describes the address of a source variable, so lower it
-    // into an indirect DBG_VALUE.
-    MIRBuilder.buildIndirectDbgValue(getOrCreateVReg(*Address),
-                                     DI.getVariable(), DI.getExpression());
+    translateDbgDeclareRecord(DI.getAddress(), DI.hasArgList(), DI.getVariable(),
+                       DI.getExpression(), DI.getDebugLoc(), MIRBuilder);
     return true;
   }
   case Intrinsic::dbg_label: {
@@ -2158,41 +2123,8 @@ bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
   case Intrinsic::dbg_value: {
     // This form of DBG_VALUE is target-independent.
     const DbgValueInst &DI = cast<DbgValueInst>(CI);
-    const Value *V = DI.getValue();
-    assert(DI.getVariable()->isValidLocationForIntrinsic(
-               MIRBuilder.getDebugLoc()) &&
-           "Expected inlined-at fields to agree");
-    if (!V || DI.hasArgList()) {
-      // DI cannot produce a valid DBG_VALUE, so produce an undef DBG_VALUE to
-      // terminate any prior location.
-      MIRBuilder.buildIndirectDbgValue(0, DI.getVariable(), DI.getExpression());
-      return true;
-    }
-    if (const auto *CI = dyn_cast<Constant>(V)) {
-      MIRBuilder.buildConstDbgValue(*CI, DI.getVariable(), DI.getExpression());
-      return true;
-    }
-    if (auto *AI = dyn_cast<AllocaInst>(V);
-        AI && AI->isStaticAlloca() && DI.getExpression()->startsWithDeref()) {
-      // If the value is an alloca and the expression starts with a
-      // dereference, track a stack slot instead of a register, as registers
-      // may be clobbered.
-      auto ExprOperands = DI.getExpression()->getElements();
-      auto *ExprDerefRemoved =
-          DIExpression::get(AI->getContext(), ExprOperands.drop_front());
-      MIRBuilder.buildFIDbgValue(getOrCreateFrameIndex(*AI), DI.getVariable(),
-                                 ExprDerefRemoved);
-      return true;
-    }
-    if (translateIfEntryValueArgument(DI, MIRBuilder))
-      return true;
-    for (Register Reg : getOrCreateVRegs(*V)) {
-      // FIXME: This does not handle register-indirect values at offset 0. The
-      // direct/indirect thing shouldn't really be handled by something as
-      // implicit as reg+noreg vs reg+imm in the first place, but it seems
-      // pretty baked in right now.
-      MIRBuilder.buildDirectDbgValue(Reg, DI.getVariable(), DI.getExpression());
-    }
+    translateDbgValueRecord(DI.getValue(), DI.hasArgList(), DI.getVariable(),
+                       DI.getExpression(), DI.getDebugLoc(), MIRBuilder);
     return true;
   }
   case Intrinsic::uadd_with_overflow:
@@ -3250,6 +3182,102 @@ void IRTranslator::finishPendingPhis() {
   }
 }
 
+void IRTranslator::translateDbgValueRecord(Value *V, bool HasArgList,
+                                     const DILocalVariable *Variable,
+                                     const DIExpression *Expression,
+                                     const DebugLoc &DL,
+                                     MachineIRBuilder &MIRBuilder) {
+  assert(Variable->isValidLocationForIntrinsic(DL) &&
+         "Expected inlined-at fields to agree");
+  // Act as if we're handling a debug intrinsic.
+  MIRBuilder.setDebugLoc(DL);
+
+  if (!V || HasArgList) {
+    // DI cannot produce a valid DBG_VALUE, so produce an undef DBG_VALUE to
+    // terminate any prior location.
+    MIRBuilder.buildIndirectDbgValue(0, Variable, Expression);
+    return;
+  }
+
+  if (const auto *CI = dyn_cast<Constant>(V)) {
+    MIRBuilder.buildConstDbgValue(*CI, Variable, Expression);
+    return;
+  }
+
+  if (auto *AI = dyn_cast<AllocaInst>(V);
+      AI && AI->isStaticAlloca() && Expression->startsWithDeref()) {
+    // If the value is an alloca and the expression starts with a
+    // dereference, track a stack slot instead of a register, as registers
+    // may be clobbered.
+    auto ExprOperands = Expression->getElements();
+    auto *ExprDerefRemoved =
+        DIExpression::get(AI->getContext(), ExprOperands.drop_front());
+    MIRBuilder.buildFIDbgValue(getOrCreateFrameIndex(*AI), Variable,
+                               ExprDerefRemoved);
+    return;
+  }
+  if (translateIfEntryValueArgument(false, V, Variable, Expression, DL,
+                                    MIRBuilder))
+    return;
+  for (Register Reg : getOrCreateVRegs(*V)) {
+    // FIXME: This does not handle register-indirect values at offset 0. The
+    // direct/indirect thing shouldn't really be handled by something as
+    // implicit as reg+noreg vs reg+imm in the first place, but it seems
+    // pretty baked in right now.
+    MIRBuilder.buildDirectDbgValue(Reg, Variable, Expression);
+  }
+  return;
+}
+
+void IRTranslator::translateDbgDeclareRecord(Value *Address, bool HasArgList,
+                                     const DILocalVariable *Variable,
+                                     const DIExpression *Expression,
+                                     const DebugLoc &DL,
+                                     MachineIRBuilder &MIRBuilder) {
+  if (!Address || isa<UndefValue>(Address)) {
+    LLVM_DEBUG(dbgs() << "Dropping debug info for " << *Variable << "\n");
+    return;
+  }
+
+  assert(Variable->isValidLocationForIntrinsic(DL) &&
+         "Expected inlined-at fields to agree");
+  auto AI = dyn_cast<AllocaInst>(Address);
+  if (AI && AI->isStaticAlloca()) {
+    // Static allocas are tracked at the MF level, no need for DBG_VALUE
+    // instructions (in fact, they get ignored if they *do* exist).
+    MF->setVariableDbgInfo(Variable, Expression,
+                           getOrCreateFrameIndex(*AI), DL);
+    return;
+  }
+
+  if (translateIfEntryValueArgument(true, Address, Variable,
+                                    Expression, DL,
+                                    MIRBuilder))
+    return;
+
+  // A dbg.declare describes the address of a source variable, so lower it
+  // into an indirect DBG_VALUE.
+  MIRBuilder.setDebugLoc(DL);
+  MIRBuilder.buildIndirectDbgValue(getOrCreateVReg(*Address),
+                                   Variable, Expression);
+  return;
+}
+
+void IRTranslator::translateDbgInfo(const Instruction &Inst,
+                                      MachineIRBuilder &MIRBuilder) {
+  for (DPValue &DPV : Inst.getDbgValueRange()) {
+    const DILocalVariable *Variable = DPV.getVariable();
+    const DIExpression *Expression = DPV.getExpression();
+    Value *V = DPV.getVariableLocationOp(0);
+    if (DPV.isDbgDeclare())
+      translateDbgDeclareRecord(V, DPV.hasArgList(), Variable,
+                         Expression, DPV.getDebugLoc(), MIRBuilder);
+    else
+      translateDbgValueRecord(V, DPV.hasArgList(), Variable,
+                         Expression, DPV.getDebugLoc(), MIRBuilder);
+  }
+}
+
 bool IRTranslator::translate(const Instruction &Inst) {
   CurBuilder->setDebugLoc(Inst.getDebugLoc());
   CurBuilder->setPCSections(Inst.getMetadata(LLVMContext::MD_pcsections));
@@ -3760,6 +3788,10 @@ bool IRTranslator::runOnMachineFunction(MachineFunction &CurMF) {
 #ifndef NDEBUG
         Verifier.setCurrentInst(&Inst);
 #endif // ifndef NDEBUG
+
+        // Translate any debug-info attached to the instruction.
+        translateDbgInfo(Inst, *CurBuilder.get());
+
         if (translate(Inst))
           continue;
 

llvm/test/CodeGen/AArch64/GlobalISel/combine-shift-of-shifted-dbg-value-fallback.ll

@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc < %s -global-isel -mtriple=arm64-linux-gnu -global-isel-abort=1 | FileCheck %s
+; RUN: llc < %s -global-isel -mtriple=arm64-linux-gnu -global-isel-abort=1 --try-experimental-debuginfo-iterators | FileCheck %s
 target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
 target triple = "arm64-apple-ios9.0.0"
 

llvm/test/CodeGen/AArch64/GlobalISel/debug-cpp.ll

@@ -1,5 +1,7 @@
 ; RUN: llc -global-isel -mtriple=aarch64 %s -stop-after=irtranslator -o - | FileCheck %s
 ; RUN: llc -mtriple=aarch64 -global-isel --global-isel-abort=0 -o /dev/null
+; RUN: llc -global-isel -mtriple=aarch64 %s -stop-after=irtranslator -o - --try-experimental-debuginfo-iterators | FileCheck %s
+; RUN: llc -mtriple=aarch64 -global-isel --global-isel-abort=0 -o /dev/null --try-experimental-debuginfo-iterators
 
 ; struct NTCopy {
 ;   NTCopy();

llvm/test/CodeGen/AArch64/GlobalISel/debug-insts.ll

@@ -2,6 +2,10 @@
 ; RUN: llc -global-isel -mtriple=aarch64 %s -stop-after=irtranslator -o - | FileCheck %s
 ; RUN: llc -mtriple=aarch64 -global-isel --global-isel-abort=0 %s -o /dev/null
 ; RUN: llc -mtriple=aarch64 -global-isel --global-isel-abort=0 %s -o /dev/null -debug
+;
+; RUN: llc -global-isel -mtriple=aarch64 %s -stop-after=irtranslator -o - --try-experimental-debuginfo-iterators | FileCheck %s
+; RUN: llc -mtriple=aarch64 -global-isel --global-isel-abort=0 %s -o /dev/null --try-experimental-debuginfo-iterators
+; RUN: llc -mtriple=aarch64 -global-isel --global-isel-abort=0 %s -o /dev/null -debug --try-experimental-debuginfo-iterators
 
 ; CHECK-LABEL: name: debug_declare
 ; CHECK: stack:

llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-dilocation.ll

@@ -1,16 +1,18 @@
 ; RUN: llc -O0 -mtriple=aarch64-apple-ios -global-isel -debug-only=irtranslator \
 ; RUN:     -stop-after=irtranslator %s -o - 2>&1 | FileCheck %s
+; RUN: llc -O0 -mtriple=aarch64-apple-ios -global-isel -debug-only=irtranslator \
+; RUN:     -stop-after=irtranslator %s -o - 2>&1 --try-experimental-debuginfo-iterators | FileCheck %s
 
 ; REQUIRES: asserts
 
-; CHECK: Checking DILocation from   %retval = alloca i32, align 4 was copied to G_FRAME_INDEX
-; CHECK: Checking DILocation from   %rv = alloca i32, align 4 was copied to G_FRAME_INDEX
-; CHECK: Checking DILocation from   store i32 0, ptr %retval, align 4 was copied to G_CONSTANT
-; CHECK: Checking DILocation from   store i32 0, ptr %retval, align 4 was copied to G_STORE
-; CHECK: Checking DILocation from   store i32 0, ptr %rv, align 4, !dbg !12 was copied to G_STORE debug-location !12; t.cpp:2:5
-; CHECK: Checking DILocation from   %0 = load i32, ptr %rv, align 4, !dbg !13 was copied to G_LOAD debug-location !13; t.cpp:3:8
-; CHECK: Checking DILocation from   ret i32 %0, !dbg !14 was copied to COPY debug-location !14; t.cpp:3:1
-; CHECK: Checking DILocation from   ret i32 %0, !dbg !14 was copied to RET_ReallyLR implicit $w0, debug-location !14; t.cpp:3:1
+; CHECK: Checking DILocation from   %retval = alloca i32, align 4{{.*}} was copied to G_FRAME_INDEX
+; CHECK: Checking DILocation from   %rv = alloca i32, align 4{{.*}} was copied to G_FRAME_INDEX
+; CHECK: Checking DILocation from   store i32 0, ptr %retval, align 4{{.*}} was copied to G_CONSTANT
+; CHECK: Checking DILocation from   store i32 0, ptr %retval, align 4{{.*}} was copied to G_STORE
+; CHECK: Checking DILocation from   store i32 0, ptr %rv, align 4, !dbg !12{{.*}} was copied to G_STORE debug-location !12; t.cpp:2:5
+; CHECK: Checking DILocation from   %0 = load i32, ptr %rv, align 4, !dbg !13{{.*}} was copied to G_LOAD debug-location !13; t.cpp:3:8
+; CHECK: Checking DILocation from   ret i32 %0, !dbg !14{{.*}} was copied to COPY debug-location !14; t.cpp:3:1
+; CHECK: Checking DILocation from   ret i32 %0, !dbg !14{{.*}} was copied to RET_ReallyLR implicit $w0, debug-location !14; t.cpp:3:1
 
 source_filename = "t.cpp"
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"

llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-extract-used-by-dbg.ll

@@ -1,4 +1,5 @@
 ; RUN: llc -O0 -stop-after=irtranslator -global-isel -verify-machineinstrs %s -o - 2>&1 | FileCheck %s
+; RUN: llc -O0 -stop-after=irtranslator -global-isel -verify-machineinstrs %s -o - 2>&1 --try-experimental-debuginfo-iterators | FileCheck %s
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64-unknown-fuchsia"

llvm/test/CodeGen/X86/GlobalISel/x86-calllowering-dbg-trunc.ll

@@ -1,4 +1,5 @@
 ; RUN: llc -mtriple=i386-linux-gnu -global-isel -verify-machineinstrs < %s -o - | FileCheck %s --check-prefix=ALL
+; RUN: llc -mtriple=i386-linux-gnu -global-isel -verify-machineinstrs < %s -o - --try-experimental-debuginfo-iterators | FileCheck %s --check-prefix=ALL
 
 ; This file is the output of clang -g -O2
 ; int test_dbg_trunc(unsigned long long a) { return a; }