[codeview] Check for a DIExpression offset for local variables

Fixes inalloca parameters, which previously all pointed to the same
offset. Extend the test to use llvm-readobj so that we can test the
offset in a readable way.

llvm-svn: 302578

2 files changed, 27 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 87b45c001de..9d60fff3bcc 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -888,13 +888,21 @@ void CodeViewDebug::collectVariableInfoFromMFTable(
     if (!Scope)
       continue;
 
+    // If the variable has an attached offset expression, extract it.
+    // FIXME: Try to handle DW_OP_deref as well.
+    int64_t ExprOffset = 0;
+    if (VI.Expr)
+      if (!VI.Expr->extractIfOffset(ExprOffset))
+        continue;
+
     // Get the frame register used and the offset.
     unsigned FrameReg = 0;
     int FrameOffset = TFI->getFrameIndexReference(*Asm->MF, VI.Slot, FrameReg);
     uint16_t CVReg = TRI->getCodeViewRegNum(FrameReg);
 
     // Calculate the label ranges.
-    LocalVarDefRange DefRange = createDefRangeMem(CVReg, FrameOffset);
+    LocalVarDefRange DefRange =
+        createDefRangeMem(CVReg, FrameOffset + ExprOffset);
     for (const InsnRange &Range : Scope->getRanges()) {
       const MCSymbol *Begin = getLabelBeforeInsn(Range.first);
       const MCSymbol *End = getLabelAfterInsn(Range.second);
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index cdbe237766a..e6c49cad072 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -672,6 +672,24 @@ void DIExpression::appendOffset(SmallVectorImpl<uint64_t> &Ops,
   }
 }
 
+bool DIExpression::extractIfOffset(int64_t &Offset) const {
+  if (getNumElements() == 0) {
+    Offset = 0;
+    return true;
+  }
+  if (getNumElements() != 2)
+    return false;
+  if (Elements[0] == dwarf::DW_OP_plus) {
+    Offset = Elements[1];
+    return true;
+  }
+  if (Elements[0] == dwarf::DW_OP_minus) {
+    Offset = -Elements[1];
+    return true;
+  }
+  return false;
+}
+
 DIExpression *DIExpression::prepend(const DIExpression *Expr, bool Deref,
                                     int64_t Offset, bool StackValue) {
   SmallVector<uint64_t, 8> Ops;