[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, 18 insertions, 0 deletions

diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 3211a5bb66d..f772276613c 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -928,6 +928,24 @@ bool DIExpression::extractIfOffset(int64_t &Offset) const {
   return false;
 }
 
+const DIExpression *DIExpression::extractAddressClass(const DIExpression *Expr,
+                                                      unsigned &AddrClass) {
+  const unsigned PatternSize = 4;
+  if (Expr->Elements.size() >= PatternSize &&
+      Expr->Elements[PatternSize - 4] == dwarf::DW_OP_constu &&
+      Expr->Elements[PatternSize - 2] == dwarf::DW_OP_swap &&
+      Expr->Elements[PatternSize - 1] == dwarf::DW_OP_xderef) {
+    AddrClass = Expr->Elements[PatternSize - 3];
+
+    if (Expr->Elements.size() == PatternSize)
+      return nullptr;
+    return DIExpression::get(Expr->getContext(),
+                             makeArrayRef(&*Expr->Elements.begin(),
+                                          Expr->Elements.size() - PatternSize));
+  }
+  return Expr;
+}
+
 DIExpression *DIExpression::prepend(const DIExpression *Expr, bool DerefBefore,
                                     int64_t Offset, bool DerefAfter,
                                     bool StackValue) {