InstCombine: salvage the debug info of DCE'ed add instructions.

rdar://problem/31209283

llvm-svn: 317522

1 files changed, 23 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index cb7978f76aa..89dbe4b8fda 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1362,16 +1362,25 @@ void llvm::salvageDebugInfo(Instruction &I) {
   SmallVector<DbgValueInst *, 1> DbgValues;
   auto &M = *I.getModule();
 
-  auto MDWrap = [&](Value *V) {
+  auto wrapMD = [&](Value *V) {
     return MetadataAsValue::get(I.getContext(), ValueAsMetadata::get(V));
   };
 
+  auto applyOffset = [&](DbgValueInst *DVI, uint64_t Offset) {
+    auto *DIExpr = DVI->getExpression();
+    DIExpr = DIExpression::prepend(DIExpr, DIExpression::NoDeref, Offset,
+                                   DIExpression::WithStackValue);
+    DVI->setOperand(0, wrapMD(I.getOperand(0)));
+    DVI->setOperand(2, MetadataAsValue::get(I.getContext(), DIExpr));
+    DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');
+  };
+
   if (isa<BitCastInst>(&I) || isa<IntToPtrInst>(&I)) {
     findDbgValues(DbgValues, &I);
     for (auto *DVI : DbgValues) {
       // Bitcasts are entirely irrelevant for debug info. Rewrite the dbg.value
       // to use the cast's source.
-      DVI->setOperand(0, MDWrap(I.getOperand(0)));
+      DVI->setOperand(0, wrapMD(I.getOperand(0)));
       DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');
     }
   } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
@@ -1383,24 +1392,26 @@ void llvm::salvageDebugInfo(Instruction &I) {
       // Rewrite a constant GEP into a DIExpression.  Since we are performing
       // arithmetic to compute the variable's *value* in the DIExpression, we
       // need to mark the expression with a DW_OP_stack_value.
-      if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
-        auto *DIExpr = DVI->getExpression();
+      if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset))
         // GEP offsets are i32 and thus always fit into an int64_t.
-        DIExpr = DIExpression::prepend(DIExpr, DIExpression::NoDeref,
-                                       Offset.getSExtValue(),
-                                       DIExpression::WithStackValue);
-        DVI->setOperand(0, MDWrap(I.getOperand(0)));
-        DVI->setOperand(2, MetadataAsValue::get(I.getContext(), DIExpr));
-        DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');
-      }
+        applyOffset(DVI, Offset.getSExtValue());
     }
+  } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
+    if (BI->getOpcode() == Instruction::Add)
+      if (auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1)))
+        if (ConstInt->getBitWidth() <= 64) {
+          APInt Offset = ConstInt->getValue();
+          findDbgValues(DbgValues, &I);
+          for (auto *DVI : DbgValues)
+            applyOffset(DVI, Offset.getSExtValue());
+        }
   } else if (isa<LoadInst>(&I)) {
     findDbgValues(DbgValues, &I);
     for (auto *DVI : DbgValues) {
       // Rewrite the load into DW_OP_deref.
       auto *DIExpr = DVI->getExpression();
       DIExpr = DIExpression::prepend(DIExpr, DIExpression::WithDeref);
-      DVI->setOperand(0, MDWrap(I.getOperand(0)));
+      DVI->setOperand(0, wrapMD(I.getOperand(0)));
       DVI->setOperand(2, MetadataAsValue::get(I.getContext(), DIExpr));
       DEBUG(dbgs() << "SALVAGE:  " << *DVI << '\n');
     }