Detect and fix invalid LLVM IR generated by bpftrace

[lenticularis39]

When running bpftrace on LLVM 14, an issue related to bpftrace generating invalid LLVM IR were encountered (see #2228, #2222 and #2296). Furthermore, other failing tests in LLVM 14 also generate invalid LLVM IR, implying this could be a more widespread issue in the codegen.

As suggested by @fbs in #2222, a verifier pass detecting LLVM IR in bpftrace output could be added to all tests to ensure these issues are identified and fixed both in the present code and in the future.

[BurntBrunch]

could be added to all tests

Locally, I found myself using this snippet to ensure all debug builds, tests or not, run through the verifier first. This has so far saved me hours as I work on codegen for new features.

diff --git a/src/ast/passes/codegen_llvm.cpp b/src/ast/passes/codegen_llvm.cpp
index e16c965f..a576e419 100644
--- a/src/ast/passes/codegen_llvm.cpp
+++ b/src/ast/passes/codegen_llvm.cpp
@@ -12,6 +12,7 @@
 #include <llvm/IR/LLVMContext.h>
 #include <llvm/IR/LegacyPassManager.h>
 #include <llvm/IR/Metadata.h>
+#include <llvm/IR/Verifier.h>
 #if LLVM_VERSION_MAJOR >= 14
 #include <llvm/Passes/PassBuilder.h>
 #endif
@@ -3154,6 +3155,14 @@ void CodegenLLVM::optimize()
 {
   assert(state_ == State::IR);
 
+#ifndef NDEBUG
+  if (verifyModule(*module_, &errs()))
+  {
+    DumpIR();
+    return;
+  }
+#endif
+
 #if LLVM_VERSION_MAJOR >= 14
   PipelineTuningOptions pto;
   pto.LoopUnrolling = false;
@@ -3185,6 +3194,7 @@ void CodegenLLVM::optimize()
   PassManagerBuilder PMB;
   PMB.OptLevel = 3;
   legacy::PassManager PM;
+  PM.add(createVerifierPass());
   PM.add(createFunctionInliningPass());
   /*
    * llvm < 4.0 needs

[lenticularis39]

Thank you for the suggestion @BurntBrunch, I implemented a solution in the linked PR by calling VerifierPass directly and doing output redirection, using verifyModule is a simpler solution.