[ASan] Make insertion of version mismatch guard configurable

[yln]

Summary

By default ASan calls a versioned function
__asan_version_mismatch_check_vXXX to ensure that the compiler ABI
version and runtime ABI version are compatible. This ensures that we get
a predictable linker error instead of hard-to-debug runtime errors.

Sometimes, however, we want to skip this safety guard. This new command
line option allows us to do just that.

rdar://47891956

[yln]

Filipe Cabecinhas <[e-mail]>
when might we not want this?

It's useful when partially transitioning a project to a new compiler version or for testing the compiler itself around the time when the version bump is actually done. Sometimes we want to test with a version-bumped compiler with the the non-version-bumped runtime or vice versa.

The flag is not meant to be used by "normal" end users. It's hidden, and we don't change the default.

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

static cl::opt<bool> ClEnableKasan(
     "asan-kernel", cl::desc("Enable KernelAddressSanitizer instrumentation"),
     cl::Hidden, cl::init(false));
 
 static cl::opt<bool> ClRecover(
     "asan-recover",
     cl::desc("Enable recovery mode (continue-after-error)."),
     cl::Hidden, cl::init(false));
 
+static cl::opt<bool> ClInsertVersionCheck(
+    "asan-guard-against-version-mismatch",
+    cl::desc("Guard against compiler/runtime version mismatch."),
+    cl::Hidden, cl::init(true));
+
 // This flag may need to be replaced with -f[no-]asan-reads.
 static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
                                        cl::desc("instrument read instructions"),
                                        cl::Hidden, cl::init(true));
 
 static cl::opt<bool> ClInstrumentWrites(
     "asan-instrument-writes", cl::desc("instrument write instructions"),
     cl::Hidden, cl::init(true));

 bool ModuleAddressSanitizer::instrumentModule(Module &M) {
   initializeCallbacks(M);
 
   if (CompileKernel)
     return false;
 
   // Create a module constructor. A destructor is created lazily because not all
   // platforms, and not all modules need it.
+  std::string AsanVersion = std::to_string(GetAsanVersion(M));
   std::string VersionCheckName =
-      kAsanVersionCheckNamePrefix + std::to_string(GetAsanVersion(M));
+      ClInsertVersionCheck ? (kAsanVersionCheckNamePrefix + AsanVersion) : "";
   std::tie(AsanCtorFunction, std::ignore) = createSanitizerCtorAndInitFunctions(
       M, kAsanModuleCtorName, kAsanInitName, /*InitArgTypes=*/{},
       /*InitArgs=*/{}, VersionCheckName);
 
   bool CtorComdat = true;
   bool Changed = false;
   // TODO(glider): temporarily disabled globals instrumentation for KASan.
   if (ClGlobals) {

llvm/test/Instrumentation/AddressSanitizer/version-mismatch-check.ll

+; Check that the ASan module constructor guards against compiler/runtime version
+; mismatch.
+
+; RUN: opt < %s -asan-module                                        -S | FileCheck %s
+; RUN: opt < %s -asan-module -asan-guard-against-version-mismatch=0 -S | FileCheck %s --check-prefix=NOGUARD
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK-LABEL: define internal void @asan.module_ctor()
+; CHECK:         call void @__asan_version_mismatch_check_v
+; NOGUARD-NOT:   call void @__asan_version_mismatch_check_v