[DebugInfo][NFC] Refactor BinOp+GEP salvaging in salvageDebugInfoImpl

This patch refactors out the salvaging of GEP and BinOp instructions into
separate functions, in preparation for further changes to the salvaging of these
instructions coming in another patch; there should be no functional change as a
result of this refactor.

Differential Revision: https://reviews.llvm.org/D92851

1 files changed, 75 insertions, 50 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 066826b..64c2042 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1836,6 +1836,75 @@ void llvm::salvageDebugInfoForDbgValues(
   }
 }
 
+bool getSalvageOpsForGEP(GetElementPtrInst *GEP, const DataLayout &DL,
+                         SmallVectorImpl<uint64_t> &Opcodes) {
+  unsigned BitWidth = DL.getIndexSizeInBits(GEP->getPointerAddressSpace());
+  // Rewrite a constant GEP into a DIExpression.
+  APInt ConstantOffset(BitWidth, 0);
+  if (!GEP->accumulateConstantOffset(DL, ConstantOffset))
+    return false;
+  DIExpression::appendOffset(Opcodes, ConstantOffset.getSExtValue());
+  return true;
+}
+
+uint64_t getDwarfOpForBinOp(Instruction::BinaryOps Opcode) {
+  switch (Opcode) {
+  case Instruction::Add:
+    return dwarf::DW_OP_plus;
+  case Instruction::Sub:
+    return dwarf::DW_OP_minus;
+  case Instruction::Mul:
+    return dwarf::DW_OP_mul;
+  case Instruction::SDiv:
+    return dwarf::DW_OP_div;
+  case Instruction::SRem:
+    return dwarf::DW_OP_mod;
+  case Instruction::Or:
+    return dwarf::DW_OP_or;
+  case Instruction::And:
+    return dwarf::DW_OP_and;
+  case Instruction::Xor:
+    return dwarf::DW_OP_xor;
+  case Instruction::Shl:
+    return dwarf::DW_OP_shl;
+  case Instruction::LShr:
+    return dwarf::DW_OP_shr;
+  case Instruction::AShr:
+    return dwarf::DW_OP_shra;
+  default:
+    // TODO: Salvage from each kind of binop we know about.
+    return 0;
+  }
+}
+
+bool getSalvageOpsForBinOp(BinaryOperator *BI,
+                           SmallVectorImpl<uint64_t> &Opcodes) {
+  // Rewrite binary operations with constant integer operands.
+  auto *ConstInt = dyn_cast<ConstantInt>(BI->getOperand(1));
+  if (!ConstInt || ConstInt->getBitWidth() > 64)
+    return false;
+  uint64_t Val = ConstInt->getSExtValue();
+  Instruction::BinaryOps BinOpcode = BI->getOpcode();
+  // Add or Sub Instructions with a constant operand can potentially be
+  // simplified.
+  if (BinOpcode == Instruction::Add || BinOpcode == Instruction::Sub) {
+    uint64_t Offset = BinOpcode == Instruction::Add ? Val : -int64_t(Val);
+    DIExpression::appendOffset(Opcodes, Offset);
+    return true;
+  }
+  // Add constant int operand to expression stack.
+  Opcodes.append({dwarf::DW_OP_constu, Val});
+
+  // Add salvaged binary operator to expression stack, if it has a valid
+  // representation in a DIExpression.
+  uint64_t DwarfBinOp = getDwarfOpForBinOp(BinOpcode);
+  if (!DwarfBinOp)
+    return false;
+  Opcodes.push_back(DwarfBinOp);
+
+  return true;
+}
+
 DIExpression *llvm::salvageDebugInfoImpl(Instruction &I,
                                          DIExpression *SrcDIExpr,
                                          bool WithStackValue, unsigned LocNo) {
@@ -1851,13 +1920,6 @@ DIExpression *llvm::salvageDebugInfoImpl(Instruction &I,
     return DIExpr;
   };
 
-  // Apply the given offset to the source DIExpression.
-  auto applyOffset = [&](uint64_t Offset) -> DIExpression * {
-    SmallVector<uint64_t, 8> Ops;
-    DIExpression::appendOffset(Ops, Offset);
-    return doSalvage(Ops);
-  };
-
   // initializer-list helper for applying operators to the source DIExpression.
   auto applyOps = [&](ArrayRef<uint64_t> Opcodes) -> DIExpression * {
     SmallVector<uint64_t, 8> Ops(Opcodes.begin(), Opcodes.end());
@@ -1883,54 +1945,17 @@ DIExpression *llvm::salvageDebugInfoImpl(Instruction &I,
                                             isa<SExtInst>(&I)));
   }
 
+  SmallVector<uint64_t, 8> Ops;
   if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
-    unsigned BitWidth =
-        M.getDataLayout().getIndexSizeInBits(GEP->getPointerAddressSpace());
-    // Rewrite a constant GEP into a DIExpression.
-    APInt Offset(BitWidth, 0);
-    if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
-      return applyOffset(Offset.getSExtValue());
-    } else {
-      return nullptr;
-    }
+    if (getSalvageOpsForGEP(GEP, DL, Ops))
+      return doSalvage(Ops);
   } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
-    // Rewrite binary operations with constant integer operands.
-    auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1));
-    if (!ConstInt || ConstInt->getBitWidth() > 64)
-      return nullptr;
-
-    uint64_t Val = ConstInt->getSExtValue();
-    switch (BI->getOpcode()) {
-    case Instruction::Add:
-      return applyOffset(Val);
-    case Instruction::Sub:
-      return applyOffset(-int64_t(Val));
-    case Instruction::Mul:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mul});
-    case Instruction::SDiv:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_div});
-    case Instruction::SRem:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mod});
-    case Instruction::Or:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_or});
-    case Instruction::And:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_and});
-    case Instruction::Xor:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_xor});
-    case Instruction::Shl:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shl});
-    case Instruction::LShr:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shr});
-    case Instruction::AShr:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shra});
-    default:
-      // TODO: Salvage constants from each kind of binop we know about.
-      return nullptr;
-    }
+    if (getSalvageOpsForBinOp(BI, Ops))
+      return doSalvage(Ops);
+  }
     // *Not* to do: we should not attempt to salvage load instructions,
     // because the validity and lifetime of a dbg.value containing
     // DW_OP_deref becomes difficult to analyze. See PR40628 for examples.
-  }
   return nullptr;
 }