Revert "[SelectionDAG] Salvage debug info for non-constant ADDs (llvm#68981)"

This reverts commit 3ab03ad. Reverted due to failing expensive-checks buildbots, e.g. https://lab.llvm.org/buildbot/#/builders/16/builds/56317. Will investigate that.

Author: dstenb

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -27,7 +27,6 @@
 #include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Analysis/VectorUtils.h"
-#include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/CodeGen/Analysis.h"
 #include "llvm/CodeGen/FunctionLoweringInfo.h"
 #include "llvm/CodeGen/ISDOpcodes.h"
@@ -10844,11 +10843,8 @@ void SelectionDAG::salvageDebugInfo(SDNode &N) {
  case ISD::ADD: {
  SDValue N0 = N.getOperand(0);
  SDValue N1 = N.getOperand(1);
- if (!isa<ConstantSDNode>(N0)) {
- bool RHSConstant = isa<ConstantSDNode>(N1);
- uint64_t Offset;
- if (RHSConstant)
- Offset = N.getConstantOperandVal(1);
+ if (!isa<ConstantSDNode>(N0) && isa<ConstantSDNode>(N1)) {
+ uint64_t Offset = N.getConstantOperandVal(1);
 
  // Rewrite an ADD constant node into a DIExpression. Since we are
  // performing arithmetic to compute the variable's *value* in the
@@ -10857,46 +10853,27 @@ void SelectionDAG::salvageDebugInfo(SDNode &N) {
  auto *DIExpr = DV->getExpression();
  auto NewLocOps = DV->copyLocationOps();
  bool Changed = false;
- size_t OrigLocOpsSize = NewLocOps.size();
- for (size_t i = 0; i < OrigLocOpsSize; ++i) {
+ for (size_t i = 0; i < NewLocOps.size(); ++i) {
  // We're not given a ResNo to compare against because the whole
  // node is going away. We know that any ISD::ADD only has one
  // result, so we can assume any node match is using the result.
  if (NewLocOps[i].getKind() != SDDbgOperand::SDNODE ||
  NewLocOps[i].getSDNode() != &N)
  continue;
  NewLocOps[i] = SDDbgOperand::fromNode(N0.getNode(), N0.getResNo());
- if (RHSConstant) {
- SmallVector<uint64_t, 3> ExprOps;
- DIExpression::appendOffset(ExprOps, Offset);
- DIExpr = DIExpression::appendOpsToArg(DIExpr, ExprOps, i, true);
- } else {
- // Convert to a variadic expression (if not already).
- // convertToVariadicExpression() returns a const pointer, so we use
- // a temporary const variable here.
- const auto *TmpDIExpr =
- DIExpression::convertToVariadicExpression(DIExpr);
- SmallVector<uint64_t, 3> ExprOps;
- ExprOps.push_back(dwarf::DW_OP_LLVM_arg);
- ExprOps.push_back(NewLocOps.size());
- ExprOps.push_back(dwarf::DW_OP_plus);
- SDDbgOperand RHS =
- SDDbgOperand::fromNode(N1.getNode(), N1.getResNo());
- NewLocOps.push_back(RHS);
- DIExpr = DIExpression::appendOpsToArg(TmpDIExpr, ExprOps, i, true);
- }
+ SmallVector<uint64_t, 3> ExprOps;
+ DIExpression::appendOffset(ExprOps, Offset);
+ DIExpr = DIExpression::appendOpsToArg(DIExpr, ExprOps, i, true);
  Changed = true;
  }
  (void)Changed;
  assert(Changed && "Salvage target doesn't use N");
 
- bool IsVariadic =
- DV->isVariadic() || OrigLocOpsSize != NewLocOps.size();
-
  auto AdditionalDependencies = DV->getAdditionalDependencies();
- SDDbgValue *Clone = getDbgValueList(
- DV->getVariable(), DIExpr, NewLocOps, AdditionalDependencies,
- DV->isIndirect(), DV->getDebugLoc(), DV->getOrder(), IsVariadic);
+ SDDbgValue *Clone = getDbgValueList(DV->getVariable(), DIExpr,
+ NewLocOps, AdditionalDependencies,
+ DV->isIndirect(), DV->getDebugLoc(),
+ DV->getOrder(), DV->isVariadic());
  ClonedDVs.push_back(Clone);
  DV->setIsInvalidated();
  DV->setIsEmitted();