[llvm] [SandboxVec][DAG] Build actual dependencies (PR #111094)

[Arthur Eubanks via llvm-commits]

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@@ -50,29 +51,136 @@ MemDGNodeIntervalBuilder::make(const Interval<Instruction> &Instrs,
                              cast<MemDGNode>(DAG.getNode(MemBotI)));
 }
 
+DependencyGraph::DependencyType
+DependencyGraph::getRoughDepType(Instruction *FromI, Instruction *ToI) {
+  // TODO: Perhaps compile-time improvement by skipping if neither is mem?
+  if (FromI->mayWriteToMemory()) {
+    if (ToI->mayReadFromMemory())
+      return DependencyType::RAW;
+    if (ToI->mayWriteToMemory())
+      return DependencyType::WAW;
+  } else if (FromI->mayReadFromMemory()) {
+    if (ToI->mayWriteToMemory())
+      return DependencyType::WAR;
+    if (ToI->mayReadFromMemory())
+      return DependencyType::RAR;
+  }
+  if (isa<sandboxir::PHINode>(FromI) || isa<sandboxir::PHINode>(ToI))
+    return DependencyType::CTRL;
+  if (ToI->isTerminator())
+    return DependencyType::CTRL;
+  if (DGNode::isStackSaveOrRestoreIntrinsic(FromI) ||
+      DGNode::isStackSaveOrRestoreIntrinsic(ToI))
+    return DependencyType::OTHER;
+  return DependencyType::NONE;
+}
+
+static bool isOrdered(Instruction *I) {
+  auto IsOrdered = [](Instruction *I) {
+    if (auto *LI = dyn_cast<LoadInst>(I))
+      return !LI->isUnordered();
+    if (auto *SI = dyn_cast<StoreInst>(I))
+      return !SI->isUnordered();
+    if (DGNode::isFenceLike(I))
+      return true;
+    return false;
+  };
+  bool Is = IsOrdered(I);
+  assert((!Is || DGNode::isMemDepCandidate(I)) &&
+         "An ordered instruction must be a MemDepCandidate!");
+  return Is;
+}
+
+bool DependencyGraph::alias(Instruction *SrcI, Instruction *DstI,
+                            DependencyType DepType) {
+  std::optional<MemoryLocation> DstLocOpt =
+      Utils::memoryLocationGetOrNone(DstI);
+  if (!DstLocOpt)
+    return true;
+  // Check aliasing.
+  assert((SrcI->mayReadFromMemory() || SrcI->mayWriteToMemory()) &&
+         "Expected a mem instr");
+  // TODO: Check AABudget
+  ModRefInfo SrcModRef =
+      isOrdered(SrcI)
+          ? ModRefInfo::Mod
----------------
aeubanks wrote:

be conservative with `ModRef`?

https://github.com/llvm/llvm-project/pull/111094