[PATCH] D70643: [DebugInfo] Support for DW_OP_implicit_pointer (DW_OP_LLVM_implicit_pointer)

[Alok Kumar Sharma via Phabricator via llvm-commits]

alok created this revision.
alok added reviewers: aprantl, probinson, dblaikie, jmorse, jini.susan.george, SouraVX, awpandey.
alok added projects: LLVM, debug-info.
Herald added subscribers: llvm-commits, hiraditya.

This patch (2/N) stems from D69787 <https://reviews.llvm.org/D69787>
It is suggested by @aprantl

  Summary:
          New dwarf operator DW_OP_LLVM_implicit_pointer is introduced (present only in LLVM IR)
          This is needed because representation and specification (types of operands) of it a bit different that actual dwarf exp

ression DW_OP_LLVM_implicit_pointer. while creating actual dwarf info it will be converted to DW_OP_LLVM_implicit_pointer.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70643

Files:
  llvm/docs/LangRef.rst
  llvm/include/llvm/BinaryFormat/Dwarf.h
  llvm/lib/BinaryFormat/Dwarf.cpp
  llvm/lib/IR/AsmWriter.cpp
  llvm/lib/IR/DebugInfoMetadata.cpp


Index: llvm/lib/IR/DebugInfoMetadata.cpp
===================================================================
--- llvm/lib/IR/DebugInfoMetadata.cpp
+++ llvm/lib/IR/DebugInfoMetadata.cpp
@@ -837,6 +837,7 @@
   case dwarf::DW_OP_LLVM_convert:
   case dwarf::DW_OP_LLVM_fragment:
   case dwarf::DW_OP_bregx:
+  case dwarf::DW_OP_LLVM_implicit_pointer:
     return 3;
   case dwarf::DW_OP_constu:
   case dwarf::DW_OP_consts:
@@ -899,6 +900,10 @@
       return I->get() == expr_op_begin()->get() && I->getArg(0) == 1 &&
              getNumElements() == 2;
     }
+    case dwarf::DW_OP_LLVM_implicit_pointer: {
+      // A DW_OP_LLVM_implicit_pointer operator must appear at the beginning
+      return I == expr_op_begin();
+    }
     case dwarf::DW_OP_LLVM_convert:
     case dwarf::DW_OP_LLVM_tag_offset:
     case dwarf::DW_OP_constu:
Index: llvm/lib/IR/AsmWriter.cpp
===================================================================
--- llvm/lib/IR/AsmWriter.cpp
+++ llvm/lib/IR/AsmWriter.cpp
@@ -2150,6 +2150,9 @@
       if (I->getOp() == dwarf::DW_OP_LLVM_convert) {
         Out << FS << I->getArg(0);
         Out << FS << dwarf::AttributeEncodingString(I->getArg(1));
+      } else if (I->getOp() == dwarf::DW_OP_LLVM_implicit_pointer) {
+        Out << FS << dwarf::OperationEncodingString(I->getArg(0));
+        Out << FS << I->getArg(1);
       } else {
         for (unsigned A = 0, AE = I->getNumArgs(); A != AE; ++A)
           Out << FS << I->getArg(A);
Index: llvm/lib/BinaryFormat/Dwarf.cpp
===================================================================
--- llvm/lib/BinaryFormat/Dwarf.cpp
+++ llvm/lib/BinaryFormat/Dwarf.cpp
@@ -151,6 +151,8 @@
     return "DW_OP_LLVM_tag_offset";
   case DW_OP_LLVM_entry_value:
     return "DW_OP_LLVM_entry_value";
+  case DW_OP_LLVM_implicit_pointer:
+    return "DW_OP_LLVM_implicit_pointer";
   }
 }
 
@@ -163,6 +165,7 @@
       .Case("DW_OP_LLVM_fragment", DW_OP_LLVM_fragment)
       .Case("DW_OP_LLVM_tag_offset", DW_OP_LLVM_tag_offset)
       .Case("DW_OP_LLVM_entry_value", DW_OP_LLVM_entry_value)
+      .Case("DW_OP_LLVM_implicit_pointer", DW_OP_LLVM_implicit_pointer)
       .Default(0);
 }
 
Index: llvm/include/llvm/BinaryFormat/Dwarf.h
===================================================================
--- llvm/include/llvm/BinaryFormat/Dwarf.h
+++ llvm/include/llvm/BinaryFormat/Dwarf.h
@@ -121,6 +121,7 @@
   DW_OP_LLVM_convert = 0x1001,     ///< Only used in LLVM metadata.
   DW_OP_LLVM_tag_offset = 0x1002,  ///< Only used in LLVM metadata.
   DW_OP_LLVM_entry_value = 0x1003, ///< Only used in LLVM metadata.
+  DW_OP_LLVM_implicit_pointer = 0x1004, ///< Only used in LLVM metadata.
 };
 
 enum TypeKind : uint8_t {
Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -4821,6 +4821,9 @@
   metadata !DIExpression(DW_OP_LLVM_arg0, DW_OP_LLVM_arg1, DW_OP_plus))``
   ``DW_OP_LLVM_arg0`` represents ``DILocalVariable("x")`` and
   ``DW_OP_LLVM_arg1`` represents ``DILocalVariable("y")``.
+- ``DW_OP_LLVM_implicit_pointer, DW_OP_LLVM_arg0 N`` can only appear at the
+  beginning of a ``DIExpression``, and it specifies the value of variable
+  represented by first operand at offset N.
 
 DWARF specifies three kinds of simple location descriptions: Register, memory,
 and implicit location descriptions.  Note that a location description is


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