[PATCH] D132221: [Assignment Tracking][2/*] Add flags to enable Assignment Tracking

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

Orlando created this revision.
Orlando added a project: debug-info.
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Herald added a project: All.
Orlando requested review of this revision.
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Herald added a project: LLVM.

The Assignment Tracking debug-info feature is outlined in this RFC <https://discourse.llvm.org/t/rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir/62367>. This first series of patches adds documentation, the changes necessary to start emitting and using the new metadata, and updates clang with an option to enable the feature. Working with the new metadata in the middle and back end will come later. There are still a few rough edges but I'm putting these patches up now hoping to get feedback on the design and implementation from the upstream community.

---

Add flags to enable Assignment Tracking:

**Enable in clang**: -Xclang -fexperimental-assignment-tracking

**Enable in llvm tools**: -experimental-assignment-tracking

When assignment tracking is enabled in clang it will pass on the flag to enable the feature in lllvm. It's undefined behaviour to read IR that contains assignment tracking primitives without specifying the feature flags.

Tests will come with later patches that add assignment tracking features.


https://reviews.llvm.org/D132221

Files:
  clang/include/clang/Basic/CodeGenOptions.def
  clang/include/clang/Driver/Options.td
  clang/lib/Driver/ToolChains/Clang.cpp
  llvm/include/llvm/IR/DebugInfo.h
  llvm/lib/IR/DebugInfo.cpp


Index: llvm/lib/IR/DebugInfo.cpp
===================================================================
--- llvm/lib/IR/DebugInfo.cpp
+++ llvm/lib/IR/DebugInfo.cpp
@@ -39,6 +39,11 @@
 using namespace llvm;
 using namespace llvm::dwarf;
 
+static cl::opt<bool>
+    ExperimentalAssignmentTracking("experimental-assignment-tracking",
+                                   cl::init(false));
+bool getEnableAssignmentTracking() { return ExperimentalAssignmentTracking; }
+
 /// Finds all intrinsics declaring local variables as living in the memory that
 /// 'V' points to. This may include a mix of dbg.declare and
 /// dbg.addr intrinsics.
Index: llvm/include/llvm/IR/DebugInfo.h
===================================================================
--- llvm/include/llvm/IR/DebugInfo.h
+++ llvm/include/llvm/IR/DebugInfo.h
@@ -159,6 +159,8 @@
   SmallPtrSet<const MDNode *, 32> NodesSeen;
 };
 
+/// Return true if assignment tracking is enabled.
+bool getEnableAssignmentTracking();
 } // end namespace llvm
 
 #endif // LLVM_IR_DEBUGINFO_H
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -6761,18 +6761,21 @@
 
   // Forward -Xclang arguments to -cc1, and -mllvm arguments to the LLVM option
   // parser.
-  // -finclude-default-header flag is for preprocessor,
-  // do not pass it to other cc1 commands when save-temps is enabled
-  if (C.getDriver().isSaveTempsEnabled() &&
-      !isa<PreprocessJobAction>(JA)) {
-    for (auto Arg : Args.filtered(options::OPT_Xclang)) {
-      Arg->claim();
-      if (StringRef(Arg->getValue()) != "-finclude-default-header")
-        CmdArgs.push_back(Arg->getValue());
+  for (auto Arg : Args.filtered(options::OPT_Xclang)) {
+    Arg->claim();
+    // -finclude-default-header flag is for preprocessor,
+    // do not pass it to other cc1 commands when save-temps is enabled
+    if (C.getDriver().isSaveTempsEnabled() &&
+        !isa<PreprocessJobAction>(JA)) {
+      if (StringRef(Arg->getValue()) == "-finclude-default-header")
+        continue;
     }
-  }
-  else {
-    Args.AddAllArgValues(CmdArgs, options::OPT_Xclang);
+    if (StringRef(Arg->getValue()) == "-fexperimental-assignment-tracking") {
+      // Add the llvm version of this flag too.
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back("-experimental-assignment-tracking");
+    }
+    CmdArgs.push_back(Arg->getValue());
   }
   for (const Arg *A : Args.filtered(options::OPT_mllvm)) {
     A->claim();
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -5283,6 +5283,11 @@
 def fdenormal_fp_math_f32_EQ : Joined<["-"], "fdenormal-fp-math-f32=">,
    Group<f_Group>;
 
+def fexperimental_assignment_tracking :
+  Flag<["-"], "fexperimental-assignment-tracking">, Group<f_Group>,
+  HelpText<"Enable assignment tracking debug info">,
+  MarshallingInfoFlag<CodeGenOpts<"EnableAssignmentTracking">>;
+
 //===----------------------------------------------------------------------===//
 // Dependency Output Options
 //===----------------------------------------------------------------------===//
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -316,6 +316,9 @@
 VALUE_CODEGENOPT(WarnStackSize     , 32, UINT_MAX) ///< Set via -fwarn-stack-size.
 CODEGENOPT(NoStackArgProbe, 1, 0) ///< Set when -mno-stack-arg-probe is used
 CODEGENOPT(DebugStrictDwarf, 1, 1) ///< Whether or not to use strict DWARF info.
+
+CODEGENOPT(EnableAssignmentTracking, 1,0)
+
 CODEGENOPT(DebugColumnInfo, 1, 0) ///< Whether or not to use column information
                                   ///< in debug info.
 


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