[Utils] Salvage debug info from dead 'or' instructions

Extend salvageDebugInfo to preserve the debug info from a dead 'or'
with a constant.

Patch by Ismail Badawi!

Differential Revision: https://reviews.llvm.org/D43129

llvm-svn: 324764

3 files changed, 32 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 68d25fe37b4..ec9340ce75c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -341,6 +341,7 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
     case dwarf::DW_OP_plus:
     case dwarf::DW_OP_minus:
     case dwarf::DW_OP_mul:
+    case dwarf::DW_OP_or:
       emitOp(Op->getOp());
       break;
     case dwarf::DW_OP_deref:
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index db097e1487d..c44bc75e02c 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -706,6 +706,7 @@ bool DIExpression::isValid() const {
     case dwarf::DW_OP_plus:
     case dwarf::DW_OP_minus:
     case dwarf::DW_OP_mul:
+    case dwarf::DW_OP_or:
     case dwarf::DW_OP_deref:
     case dwarf::DW_OP_xderef:
       break;
@@ -772,6 +773,12 @@ DIExpression *DIExpression::prepend(const DIExpression *Expr, bool DerefBefore,
   if (DerefAfter)
     Ops.push_back(dwarf::DW_OP_deref);
 
+  return doPrepend(Expr, Ops, StackValue);
+}
+
+DIExpression *DIExpression::doPrepend(const DIExpression *Expr,
+                                      SmallVectorImpl<uint64_t> &Ops,
+                                      bool StackValue) {
   if (Expr)
     for (auto Op : Expr->expr_ops()) {
       // A DW_OP_stack_value comes at the end, but before a DW_OP_LLVM_fragment.
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 337ee0e9ef5..39169f931b7 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1497,16 +1497,27 @@ void llvm::salvageDebugInfo(Instruction &I) {
     return MetadataAsValue::get(I.getContext(), ValueAsMetadata::get(V));
   };
 
-  auto applyOffset = [&](DbgInfoIntrinsic *DII, uint64_t Offset) {
+  auto doSalvage = [&](DbgInfoIntrinsic *DII, SmallVectorImpl<uint64_t> &Ops) {
     auto *DIExpr = DII->getExpression();
-    DIExpr = DIExpression::prepend(DIExpr, DIExpression::NoDeref, Offset,
-                                   DIExpression::NoDeref,
-                                   DIExpression::WithStackValue);
+    DIExpr = DIExpression::doPrepend(DIExpr, Ops,
+                                     DIExpression::WithStackValue);
     DII->setOperand(0, wrapMD(I.getOperand(0)));
     DII->setOperand(2, MetadataAsValue::get(I.getContext(), DIExpr));
     DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
   };
 
+  auto applyOffset = [&](DbgInfoIntrinsic *DII, uint64_t Offset) {
+    SmallVector<uint64_t, 8> Ops;
+    DIExpression::appendOffset(Ops, Offset);
+    doSalvage(DII, Ops);
+  };
+
+  auto applyOps = [&](DbgInfoIntrinsic *DII,
+                      std::initializer_list<uint64_t> Opcodes) {
+    SmallVector<uint64_t, 8> Ops(Opcodes);
+    doSalvage(DII, Ops);
+  };
+
   if (isa<BitCastInst>(&I) || isa<IntToPtrInst>(&I)) {
     // Bitcasts are entirely irrelevant for debug info. Rewrite dbg.value,
     // dbg.addr, and dbg.declare to use the cast's source.
@@ -1525,11 +1536,17 @@ void llvm::salvageDebugInfo(Instruction &I) {
       for (auto *DII : DbgUsers)
         applyOffset(DII, Offset.getSExtValue());
   } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
-    if (BI->getOpcode() == Instruction::Add)
+    if (BI->getOpcode() == Instruction::Add ||
+        BI->getOpcode() == Instruction::Or)
       if (auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1)))
-        if (ConstInt->getBitWidth() <= 64)
+        if (ConstInt->getBitWidth() <= 64) {
+          uint64_t Val = ConstInt->getSExtValue();
           for (auto *DII : DbgUsers)
-            applyOffset(DII, ConstInt->getSExtValue());
+            if (BI->getOpcode() == Instruction::Add)
+              applyOffset(DII, Val);
+            else if (BI->getOpcode() == Instruction::Or)
+              applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_or});
+        }
   } else if (isa<LoadInst>(&I)) {
     MetadataAsValue *AddrMD = wrapMD(I.getOperand(0));
     for (auto *DII : DbgUsers) {