From b905b4697ef2864e7a6a03db61b0fe3b0ae867fa Mon Sep 17 00:00:00 2001
From: Marek Chalupa <chalupa@fi.muni.cz>
Date: Thu, 14 Oct 2021 15:57:47 +0200
Subject: [PATCH] llvm-dg: preserve dbg intrinsic

We usually want them in the sliced code.

Part of a fix for https://github.com/staticafi/symbiotic/issues/202
---
 include/dg/llvm/LLVMDependenceGraph.h        |  2 +-
 include/dg/llvm/LLVMDependenceGraphBuilder.h |  5 +--
 lib/llvm/LLVMDependenceGraph.cpp             | 34 +++++++++++++++++++-
 tools/llvm-slicer-opts.cpp                   |  6 ++++
 4 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/include/dg/llvm/LLVMDependenceGraph.h b/include/dg/llvm/LLVMDependenceGraph.h
index 1aa877ad9..11fb59dea 100644
--- a/include/dg/llvm/LLVMDependenceGraph.h
+++ b/include/dg/llvm/LLVMDependenceGraph.h
@@ -139,7 +139,7 @@ class LLVMDependenceGraph : public DependenceGraph<LLVMNode> {
 
     LLVMNode *findNode(llvm::Value *value) const;
 
-    void addDefUseEdges();
+    void addDefUseEdges(bool preserveDbg = true);
     void computeInterferenceDependentEdges(ControlFlowGraph *controlFlowGraph);
     static void computeForkJoinDependencies(ControlFlowGraph *controlFlowGraph);
     static void computeCriticalSections(ControlFlowGraph *controlFlowGraph);
diff --git a/include/dg/llvm/LLVMDependenceGraphBuilder.h b/include/dg/llvm/LLVMDependenceGraphBuilder.h
index ed978cbf4..688de6b89 100644
--- a/include/dg/llvm/LLVMDependenceGraphBuilder.h
+++ b/include/dg/llvm/LLVMDependenceGraphBuilder.h
@@ -40,6 +40,7 @@ struct LLVMDependenceGraphOptions {
 
     bool verifyGraph{true};
     bool threads{false};
+    bool preserveDbg{true};
 
     std::string entryFunction{"main"};
 
@@ -164,7 +165,7 @@ class LLVMDependenceGraphBuilder {
         _dg->build(_M, _PTA.get(), _DDA.get(), _entryFunction);
 
         // insert the data dependencies edges
-        _dg->addDefUseEdges();
+        _dg->addDefUseEdges(_options.preserveDbg);
 
         // compute and fill-in control dependencies
         _runControlDependenceAnalysis();
@@ -228,7 +229,7 @@ class LLVMDependenceGraphBuilder {
 
         // data-dependence edges
         _runDataDependenceAnalysis();
-        _dg->addDefUseEdges();
+        _dg->addDefUseEdges(_options.preserveDbg);
 
         // fill-in control dependencies
         _runControlDependenceAnalysis();
diff --git a/lib/llvm/LLVMDependenceGraph.cpp b/lib/llvm/LLVMDependenceGraph.cpp
index 1b46c3fab..74e7f48cd 100644
--- a/lib/llvm/LLVMDependenceGraph.cpp
+++ b/lib/llvm/LLVMDependenceGraph.cpp
@@ -12,6 +12,7 @@
 
 #include <llvm/IR/DataLayout.h>
 #include <llvm/IR/Function.h>
+#include <llvm/IR/InstIterator.h>
 #include <llvm/IR/Instructions.h>
 #include <llvm/IR/Module.h>
 #include <llvm/IR/Value.h>
@@ -1241,9 +1242,40 @@ void LLVMDependenceGraph::addNoreturnDependencies(
     }
 }
 
-void LLVMDependenceGraph::addDefUseEdges() {
+void LLVMDependenceGraph::addDefUseEdges(bool preserveDbg) {
     LLVMDefUseAnalysis DUA(this, DDA, PTA);
     DUA.run();
+
+    if (preserveDbg) {
+        using namespace llvm;
+
+        for (const auto &it : getConstructedFunctions()) {
+            LLVMDependenceGraph *dg = it.second;
+            for (auto &I : instructions(cast<Function>(it.first))) {
+                Value *val = nullptr;
+                if (auto *DI = dyn_cast<DbgDeclareInst>(&I))
+                    val = DI->getAddress();
+                else if (auto *DI = dyn_cast<DbgValueInst>(&I))
+                    val = DI->getValue();
+#if LLVM_VERSION_MAJOR > 5
+                else if (auto *DI = dyn_cast<DbgAddrIntrinsic>(&I))
+                    val = DI->getAddress();
+#endif
+
+                if (val) {
+                    auto *nd = dg->getNode(&I);
+                    auto *ndop = dg->getNode(val);
+                    assert(nd && "Do not have a node for a dbg intrinsic");
+                    assert(ndop && "Do not have a node for an operand of a dbg "
+                                   "intrinsic");
+                    // add a use edge such that we preserve
+                    // the debugging intrinsic when we preserve
+                    // the value it is talking about
+                    nd->addUseDependence(ndop);
+                }
+            }
+        }
+    }
 }
 
 LLVMNode *findInstruction(llvm::Instruction *instruction,
diff --git a/tools/llvm-slicer-opts.cpp b/tools/llvm-slicer-opts.cpp
index 966e9d04d..e4a108b8b 100644
--- a/tools/llvm-slicer-opts.cpp
+++ b/tools/llvm-slicer-opts.cpp
@@ -209,6 +209,11 @@ SlicerOptions parseSlicerOptions(int argc, char *argv[], bool requireCrit,
                     "Consider threads are in input file (default=false)."),
             llvm::cl::init(false), llvm::cl::cat(SlicingOpts));
 
+    llvm::cl::opt<bool> preserveDbg(
+            "preserve-dbg",
+            llvm::cl::desc("Preserve debugging information (default=true)."),
+            llvm::cl::init(true), llvm::cl::cat(SlicingOpts));
+
     llvm::cl::opt<std::string> allocationFuns(
             "allocation-funs",
             llvm::cl::desc(
@@ -380,6 +385,7 @@ SlicerOptions parseSlicerOptions(int argc, char *argv[], bool requireCrit,
     auto &CDAOptions = dgOptions.CDAOptions;
 
     dgOptions.entryFunction = entryFunction;
+    dgOptions.preserveDbg = preserveDbg;
     dgOptions.threads = threads;
 
     CDAOptions.algorithm = cdAlgorithm;