-fsanitize=function: use type hashes instead of RTTI objects

Currently we use RTTI objects to check type compatibility. To support non-unique
RTTI objects, commit 5745eccef54ddd3caca278d1d292a88b2281528b added a
`checkTypeInfoEquality` string matching to the runtime.
The scheme is inefficient.

```
_Z1fv:
  .long   846595819                    # jmp
  .long   .L__llvm_rtti_proxy-_Z3funv
  ...

main:
  ...
  # Load the second word (pointer to the RTTI object) and dereference it.
  movslq  4(%rsi), %rax
  movq    (%rax,%rsi), %rdx
  # Is it the desired typeinfo object?
  leaq    _ZTIFvvE(%rip), %rax
  # If not, call __ubsan_handle_function_type_mismatch_v1, which may recover if checkTypeInfoEquality allows
  cmpq    %rax, %rdx
  jne     .LBB1_2
  ...

.section        .data.rel.ro,"aw",@progbits
  .p2align        3, 0x0
.L__llvm_rtti_proxy:
  .quad   _ZTIFvvE
```

Let's replace the indirect `_ZTI` pointer with a type hash similar to
`-fsanitize=kcfi`.

```
_Z1fv:
  .long   3238382334
  .long   2772461324  # type hash

main:
  ...
  # Load the second word (callee type hash) and check whether it is expected
  cmpl    $-1522505972, -4(%rax)
  # If not, fail: call __ubsan_handle_function_type_mismatch
  jne     .LBB2_2
```

The RTTI object derives its name from `clang::MangleContext::mangleCXXRTTI`,
which uses `mangleType`. `mangleTypeName` uses `mangleType` as well. So the
type compatibility change is high-fidelity.

Since we no longer need RTTI pointers in
`__ubsan::__ubsan_handle_function_type_mismatch_v1`, let's switch it back to
version 0, the original signature before
e215996a2932ed7c472f4e94dc4345b30fd0c373 (2019).
`__ubsan::__ubsan_handle_function_type_mismatch_abort` is not
recoverable, so we can revert some changes from
e215996a2932ed7c472f4e94dc4345b30fd0c373.

Reviewed By: samitolvanen

Differential Revision: https://reviews.llvm.org/D148785

0 files changed, 0 insertions, 0 deletions