[DEBUG_INFO][NVPTX] Generate DW_AT_address_class to get the values in debugger.

Summary:
According to
https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf,
the compiler should emit the DW_AT_address_class attribute for all
variable and parameter. It means, that DW_AT_address_class attribute
should be used in the non-standard way to support compatibility with the
cuda-gdb debugger.
Clang is able to generate the information about the variable address
class. This information is emitted as the expression sequence
`DW_OP_constu <DWARF Address Space> DW_OP_swap DW_OP_xderef`. The patch
tries to find all such expressions and transform them into
`DW_AT_address_class <DWARF Address Space>` if target is NVPTX and the debugger is gdb.
If the expression is not found, then default values are used. For the
local variables <DWARF Address Space> is set to ADDR_local_space(6), for
the globals <DWARF Address Space> is set to ADDR_global_space(5). The
values are taken from the table in the same section 5.2. CUDA-Specific
DWARF Definitions.

Reviewers: echristo, probinson

Subscribers: jholewinski, aprantl, llvm-commits

Differential Revision: https://reviews.llvm.org/D57157

llvm-svn: 353203

1 files changed, 54 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index ec136a6bc4c..0a30ede2d2d 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -167,6 +167,7 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
   // Add location.
   bool addToAccelTable = false;
   DIELoc *Loc = nullptr;
+  Optional<unsigned> NVPTXAddressSpace;
   std::unique_ptr<DIEDwarfExpression> DwarfExpr;
   for (const auto &GE : GlobalExprs) {
     const GlobalVariable *Global = GE.Var;
@@ -200,8 +201,24 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
       DwarfExpr = llvm::make_unique<DIEDwarfExpression>(*Asm, *this, *Loc);
     }
 
-    if (Expr)
+    if (Expr) {
+      // According to
+      // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+      // cuda-gdb requires DW_AT_address_class for all variables to be able to
+      // correctly interpret address space of the variable address.
+      // Decode DW_OP_constu <DWARF Address Space> DW_OP_swap DW_OP_xderef
+      // sequence for the NVPTX + gdb target.
+      unsigned LocalNVPTXAddressSpace;
+      if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+        const DIExpression *NewExpr =
+            DIExpression::extractAddressClass(Expr, LocalNVPTXAddressSpace);
+        if (NewExpr != Expr) {
+          Expr = NewExpr;
+          NVPTXAddressSpace = LocalNVPTXAddressSpace;
+        }
+      }
       DwarfExpr->addFragmentOffset(Expr);
+    }
 
     if (Global) {
       const MCSymbol *Sym = Asm->getSymbol(Global);
@@ -246,6 +263,15 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
       DwarfExpr->setMemoryLocationKind();
     DwarfExpr->addExpression(Expr);
   }
+  if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+    // According to
+    // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+    // cuda-gdb requires DW_AT_address_class for all variables to be able to
+    // correctly interpret address space of the variable address.
+    const unsigned NVPTX_ADDR_global_space = 5;
+    addUInt(*VariableDIE, dwarf::DW_AT_address_class, dwarf::DW_FORM_data1,
+            NVPTXAddressSpace ? *NVPTXAddressSpace : NVPTX_ADDR_global_space);
+  }
   if (Loc)
     addBlock(*VariableDIE, dwarf::DW_AT_location, DwarfExpr->finalize());
 
@@ -591,6 +617,7 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
   if (!DV.hasFrameIndexExprs())
     return VariableDie;
 
+  Optional<unsigned> NVPTXAddressSpace;
   DIELoc *Loc = new (DIEValueAllocator) DIELoc;
   DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
   for (auto &Fragment : DV.getFrameIndexExprs()) {
@@ -602,7 +629,23 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
     SmallVector<uint64_t, 8> Ops;
     Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(Offset);
-    Ops.append(Expr->elements_begin(), Expr->elements_end());
+    // According to
+    // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+    // cuda-gdb requires DW_AT_address_class for all variables to be able to
+    // correctly interpret address space of the variable address.
+    // Decode DW_OP_constu <DWARF Address Space> DW_OP_swap DW_OP_xderef
+    // sequence for the NVPTX + gdb target.
+    unsigned LocalNVPTXAddressSpace;
+    if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+      const DIExpression *NewExpr =
+          DIExpression::extractAddressClass(Expr, LocalNVPTXAddressSpace);
+      if (NewExpr != Expr) {
+        Expr = NewExpr;
+        NVPTXAddressSpace = LocalNVPTXAddressSpace;
+      }
+    }
+    if (Expr)
+      Ops.append(Expr->elements_begin(), Expr->elements_end());
     DIExpressionCursor Cursor(Ops);
     DwarfExpr.setMemoryLocationKind();
     if (const MCSymbol *FrameSymbol = Asm->getFunctionFrameSymbol())
@@ -612,6 +655,15 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
           *Asm->MF->getSubtarget().getRegisterInfo(), Cursor, FrameReg);
     DwarfExpr.addExpression(std::move(Cursor));
   }
+  if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+    // According to
+    // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+    // cuda-gdb requires DW_AT_address_class for all variables to be able to
+    // correctly interpret address space of the variable address.
+    const unsigned NVPTX_ADDR_local_space = 6;
+    addUInt(*VariableDie, dwarf::DW_AT_address_class, dwarf::DW_FORM_data1,
+            NVPTXAddressSpace ? *NVPTXAddressSpace : NVPTX_ADDR_local_space);
+  }
   addBlock(*VariableDie, dwarf::DW_AT_location, DwarfExpr.finalize());
 
   return VariableDie;