[ASan] Do not instrument other runtime functions with `__asan_handle_no_return`

[yln]

Summary

Currently, ASan inserts a call to __asan_handle_no_return before every
noreturn function call/invoke. This is unnecessary for calls to other
runtime funtions. This patch changes ASan to skip instrumentation for
functions calls marked with !nosanitize metadata.

[vsk]

Looks reasonable to me.

llvm/test/Instrumentation/AddressSanitizer/instrument-no-return.ll

3 ↗

(On Diff #184410)

Could you make this more specific? E.g. 'noreturn calls that aren't inserted by sanitizers'.

[eugenis]

Do we have a test that at most one __asan_handle_no_return call is inserted before a [[noreturn]] call?

[yln]

Improve comments.
Use CHECK-NEXT in test to ensure we insert exactly one handler call.

[eugenis]

LGTM

[yln]

@vsk Any more comments?

[vsk]

Thanks, lgtm!

lib/CodeGen/CGCall.cpp

#endif
   // insertion point; this allows the rest of IRGen to discard
   // unreachable code.
   if (CI->doesNotReturn()) {
     if (UnusedReturnSizePtr)
       PopCleanupBlock();
 
     // Strip away the noreturn attribute to better diagnose unreachable UB.
     if (SanOpts.has(SanitizerKind::Unreachable)) {
-      // Also remove from function since CI->hasFnAttr(..) also checks attributes
-      // of the called function.
+      // Also remove from function since CallBase::hasFnAttr additionally checks
+      // attributes of the called function.
       if (auto *F = CI->getCalledFunction())
         F->removeFnAttr(llvm::Attribute::NoReturn);
       CI->removeAttribute(llvm::AttributeList::FunctionIndex,
                           llvm::Attribute::NoReturn);
 
       // Avoid incompatibility with ASan which relies on the `noreturn`
       // attribute to insert handler calls.
       if (SanOpts.has(SanitizerKind::Address)) {

test/CodeGen/ubsan-asan-noreturn.c

 // Ensure compatiblity of UBSan unreachable with ASan in the presence of
 // noreturn functions.
 // RUN: %clang_cc1 -fsanitize=unreachable,address -triple x86_64-linux -emit-llvm -o - %s | FileCheck %s
 
 void my_longjmp(void) __attribute__((noreturn));
 
 // CHECK-LABEL: define void @calls_noreturn()
 void calls_noreturn() {
   my_longjmp();
   // CHECK:      @__asan_handle_no_return{{.*}} !nosanitize
   // CHECK-NEXT: @my_longjmp(){{[^#]*}}
-  // CHECK:      @__asan_handle_no_return()
-  // CHECK-NEXT: @__ubsan_handle_builtin_unreachable{{.*}} !nosanitize
+  // CHECK:      @__ubsan_handle_builtin_unreachable{{.*}} !nosanitize
   // CHECK-NEXT: unreachable
 }
 
 // CHECK: declare void @my_longjmp() [[FN_ATTR:#[0-9]+]]
 // CHECK: declare void @__asan_handle_no_return()
 
 // CHECK-LABEL: attributes
 // CHECK-NOT: [[FN_ATTR]] = { {{.*noreturn.*}} }