DebugInfo: PR14763/r183329 correct the location of indirect parameters

We had been papering over a problem with location info for non-trivial
types passed by value by emitting their type as references (this caused
the debugger to interpret the location information correctly, but broke
the type of the function). r183329 corrected the type information but
lead to the debugger interpreting the pointer parameter as the value -
the debug info describing the location needed an extra dereference.

Use a new flag in DIVariable to add the extra indirection (either by
promoting an existing DW_OP_reg (parameter passed in a register) to
DW_OP_breg + 0 or by adding DW_OP_deref to an existing DW_OP_breg + n
(parameter passed on the stack).

llvm-svn: 184368

2 files changed, 10 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 79117d9f9b9..8cd7b9db593 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -812,7 +812,8 @@ void AsmPrinter::EmitFunctionBody() {
 }
 
 /// EmitDwarfRegOp - Emit dwarf register operation.
-void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
+void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc,
+                                bool Indirect) const {
   const TargetRegisterInfo *TRI = TM.getRegisterInfo();
   int Reg = TRI->getDwarfRegNum(MLoc.getReg(), false);
 
@@ -830,7 +831,7 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
   // caller might be in the middle of an dwarf expression. We should
   // probably assert that Reg >= 0 once debug info generation is more mature.
 
-  if (MLoc.isIndirect()) {
+  if (MLoc.isIndirect() || Indirect) {
     if (Reg < 32) {
       OutStreamer.AddComment(
         dwarf::OperationEncodingString(dwarf::DW_OP_breg0 + Reg));
@@ -841,7 +842,9 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
       OutStreamer.AddComment(Twine(Reg));
       EmitULEB128(Reg);
     }
-    EmitSLEB128(MLoc.getOffset());
+    EmitSLEB128(!MLoc.isIndirect() ? 0 : MLoc.getOffset());
+    if (MLoc.isIndirect() && Indirect)
+      EmitInt8(dwarf::DW_OP_deref);
   } else {
     if (Reg < 32) {
       OutStreamer.AddComment(
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 23eb569c6ff..130e29595b8 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2443,7 +2443,7 @@ void DwarfDebug::emitDebugLoc() {
       } else if (Entry.isLocation()) {
         if (!DV.hasComplexAddress())
           // Regular entry.
-          Asm->EmitDwarfRegOp(Entry.Loc);
+          Asm->EmitDwarfRegOp(Entry.Loc, DV.isIndirect());
         else {
           // Complex address entry.
           unsigned N = DV.getNumAddrElements();
@@ -2451,7 +2451,7 @@ void DwarfDebug::emitDebugLoc() {
           if (N >= 2 && DV.getAddrElement(0) == DIBuilder::OpPlus) {
             if (Entry.Loc.getOffset()) {
               i = 2;
-              Asm->EmitDwarfRegOp(Entry.Loc);
+              Asm->EmitDwarfRegOp(Entry.Loc, DV.isIndirect());
               Asm->OutStreamer.AddComment("DW_OP_deref");
               Asm->EmitInt8(dwarf::DW_OP_deref);
               Asm->OutStreamer.AddComment("DW_OP_plus_uconst");
@@ -2461,11 +2461,11 @@ void DwarfDebug::emitDebugLoc() {
               // If first address element is OpPlus then emit
               // DW_OP_breg + Offset instead of DW_OP_reg + Offset.
               MachineLocation Loc(Entry.Loc.getReg(), DV.getAddrElement(1));
-              Asm->EmitDwarfRegOp(Loc);
+              Asm->EmitDwarfRegOp(Loc, DV.isIndirect());
               i = 2;
             }
           } else {
-            Asm->EmitDwarfRegOp(Entry.Loc);
+            Asm->EmitDwarfRegOp(Entry.Loc, DV.isIndirect());
           }
 
           // Emit remaining complex address elements.