[llvm] Add -verify-with-context option to enable better reporting of verifier errors (PR #84867)

[Matt Arsenault via llvm-commits]

================
@@ -132,9 +132,64 @@ static cl::opt<bool> VerifyNoAliasScopeDomination(
     cl::desc("Ensure that llvm.experimental.noalias.scope.decl for identical "
              "scopes are not dominating"));
 
+static cl::opt<bool> VerifyWithContext(
+    "verify-with-context", cl::Hidden, cl::init(false),
+    cl::desc("Enable a detailed context reporting for verification errors"));
+
 namespace llvm {
 
-struct VerifierSupport {
+/// Helper type to manage the current context of a Verifier.
+struct VerifierCtxManager {
+  /// Current context.
+  SmallVector<const Value *> ContextPath;
+  /// The number of the current instruction in the current basic block.
+  size_t CurInstNumInThisBlock;
+
+  VerifierCtxManager() : CurInstNumInThisBlock(0) {}
+
+  void pushCtx(const Value *V) {
+    if (isa<Instruction>(V))
+      CurInstNumInThisBlock++;
+    else if (isa<BasicBlock>(V) || isa<Function>(V))
+      CurInstNumInThisBlock = 0;
+    ContextPath.emplace_back(V);
+  }
+  void popCtx() { ContextPath.pop_back(); }
+  void printCtx(raw_ostream &OS, bool NL = false) {
+    if (ContextPath.empty())
+      return;
+    OS << "Context [";
+    for (size_t i = 0; i < ContextPath.size(); ++i) {
+      if (i > 0) {
+        OS << " -> ";
+      }
+      auto C = ContextPath[i];
+      if (isa<Function>(C)) {
+        OS << "Function '";
+      } else if (isa<BasicBlock>(C)) {
+        OS << "BasicBlock '";
+      } else if (isa<Instruction>(C)) {
+        OS << "Instruction '";
+      } else {
+        OS << "Value '";
+      }
+      OS << C->getName() << "'";
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arsenm wrote:

This won't be friendly with anonymous values 

https://github.com/llvm/llvm-project/pull/84867