InlineHelpers: add post-inlining no-GEP verifier

Add `PostInlineHelpersVerifyPass`, a `ModulePass` derived class that
aborts on any `getelementptr` instruction found in any Isolated
function. `inline-helpers` is the only pass in the post-isolate chain
that could import a GEP into an Isolated function by inlining a helper
body that contains one, so the verifier is invoked at the end of
`InlineHelpersPass::runOnModule`. In this way, we early catch this
invariant on the IR.

lib/FunctionIsolation/CMakeLists.txt

@@ -8,6 +8,7 @@ revng_add_analyses_library_internal(
   InlineHelpers.cpp
   InvokeIsolatedFunctions.cpp
   IsolateFunctions.cpp
+  PostInlineHelpersVerifyPass.cpp
   PromoteCSVs.cpp
   RemoveExceptionalCalls.cpp
   StripDebugInfoFromHelpers.cpp

lib/FunctionIsolation/InlineHelpers.cpp

@@ -24,6 +24,8 @@
 #include "revng/Support/OpaqueFunctionsPool.h"
 #include "revng/Support/ResourceFinder.h"
 
+#include "PostInlineHelpersVerifyPass.h"
+
 using namespace llvm;
 
 static Logger Log("inline-helpers");
@@ -272,5 +274,11 @@ bool InlineHelpersPass::runOnModule(llvm::Module &M) {
       deleteOnlyBody(F);
   }
 
+  // Verify that no `getelementptr` instruction was dragged into an Isolated
+  // function by the inlining above. The downstream pipeline relies on this
+  // invariant.
+  // TODO: convert this from a pass to a free-standing function
+  PostInlineHelpersVerifyPass{}.runOnModule(M);
+
   return true;
 }

lib/FunctionIsolation/PostInlineHelpersVerifyPass.cpp

@@ -0,0 +1,34 @@
+//
+// This file is distributed under the MIT License. See LICENSE.md for details.
+//
+
+#include "llvm/IR/Function.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+
+#include "revng/Model/FunctionTags.h"
+#include "revng/Support/Assert.h"
+#include "revng/Support/IRHelpers.h"
+
+#include "PostInlineHelpersVerifyPass.h"
+
+using namespace llvm;
+
+bool PostInlineHelpersVerifyPass::runOnModule(Module &M) {
+  for (Function &F : M) {
+    if (not FunctionTags::Isolated.isTagOf(&F))
+      continue;
+
+    for (Instruction &I : instructions(F))
+      if (isa<GetElementPtrInst>(&I))
+        revng_abort(("post-inline-helpers-verify: "
+                     "getelementptr in Isolated function "
+                     + F.getName().str())
+                      .c_str());
+  }
+
+  return false;
+}
+
+char PostInlineHelpersVerifyPass::ID;

lib/FunctionIsolation/PostInlineHelpersVerifyPass.h

@@ -0,0 +1,20 @@
+#pragma once
+
+//
+// This file is distributed under the MIT License. See LICENSE.md for details.
+//
+
+#include "llvm/Pass.h"
+
+/// Module pass that asserts no `getelementptr` instruction remains in any
+/// `Isolated` function after the `inline-helpers` pass has run.
+class PostInlineHelpersVerifyPass : public llvm::ModulePass {
+public:
+  static char ID;
+
+public:
+  PostInlineHelpersVerifyPass() : llvm::ModulePass(ID) {}
+
+public:
+  bool runOnModule(llvm::Module &M) final;
+};