[llvm] Verifier: More helpful error message for cross-function references (PR #82906)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle created https://github.com/llvm/llvm-project/pull/82906

This came up on Discourse.

See: https://discourse.llvm.org/t/module-verification-failed-instruction-does-not-dominate-all-uses/77207/

>From 11f2ca1dd99a4ecadbcf0e0589580adc4396aa9d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <nicolai.haehnle at amd.com>
Date: Sun, 25 Feb 2024 05:34:00 +0100
Subject: [PATCH] Verifier: More helpful error message for cross-function
 references

This came up on Discourse.

See: https://discourse.llvm.org/t/module-verification-failed-instruction-does-not-dominate-all-uses/77207/
---
 llvm/lib/IR/Verifier.cpp           |  4 +++-
 llvm/unittests/IR/VerifierTest.cpp | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index b04d39c700a8f5..94f3be6a2f0c65 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -4963,7 +4963,9 @@ void Verifier::visitInstruction(Instruction &I) {
     } else if (GlobalValue *GV = dyn_cast<GlobalValue>(I.getOperand(i))) {
       Check(GV->getParent() == &M, "Referencing global in another module!", &I,
             &M, GV, GV->getParent());
-    } else if (isa<Instruction>(I.getOperand(i))) {
+    } else if (Instruction *OpInst = dyn_cast<Instruction>(I.getOperand(i))) {
+      Check(OpInst->getFunction() == BB->getParent(),
+            "Referring to an instruction in another function!", &I);
       verifyDominatesUse(I, i);
     } else if (isa<InlineAsm>(I.getOperand(i))) {
       Check(CBI && &CBI->getCalledOperandUse() == &I.getOperandUse(i),
diff --git a/llvm/unittests/IR/VerifierTest.cpp b/llvm/unittests/IR/VerifierTest.cpp
index 31e3b9dfab4bfd..b2cd71e6a38568 100644
--- a/llvm/unittests/IR/VerifierTest.cpp
+++ b/llvm/unittests/IR/VerifierTest.cpp
@@ -339,5 +339,33 @@ TEST(VerifierTest, SwitchInst) {
   EXPECT_TRUE(verifyFunction(*F));
 }
 
+TEST(VerifierTest, CrossFunctionRef) {
+  LLVMContext C;
+  Module M("M", C);
+  FunctionType *FTy = FunctionType::get(Type::getVoidTy(C), /*isVarArg=*/false);
+  Function *F1 = Function::Create(FTy, Function::ExternalLinkage, "foo1", M);
+  Function *F2 = Function::Create(FTy, Function::ExternalLinkage, "foo2", M);
+  BasicBlock *Entry1 = BasicBlock::Create(C, "entry", F1);
+  BasicBlock *Entry2 = BasicBlock::Create(C, "entry", F2);
+  Type *I32 = Type::getInt32Ty(C);
+
+  Value *Alloca = new AllocaInst(I32, 0, "alloca", Entry1);
+  ReturnInst::Create(C, Entry1);
+
+  Instruction *Store = new StoreInst(ConstantInt::get(I32, 0), Alloca, Entry2);
+  ReturnInst::Create(C, Entry2);
+
+  std::string Error;
+  raw_string_ostream ErrorOS(Error);
+  EXPECT_TRUE(verifyModule(M, &ErrorOS));
+  EXPECT_TRUE(
+      StringRef(ErrorOS.str())
+          .starts_with("Referring to an instruction in another function!"));
+
+  // Explicitly erase the store to avoid a use-after-free when the module is
+  // destroyed.
+  Store->eraseFromParent();
+}
+
 } // end anonymous namespace
 } // end namespace llvm