[IR] Introduce llvm.allow.{runtime,ubsan}.check()

llvm/docs/LangRef.rst

@@ -27696,6 +27696,121 @@ constant `true`. However it is always correct to replace
 it with any other `i1` value. Any pass can
 freely do it if it can benefit from non-default lowering.
 
+'``llvm.allow.ubsan.check``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i1 @llvm.allow.ubsan.check(i8 immarg %kind)
+
+Overview:
+"""""""""
+
+This intrinsic returns ``true`` if and only if the compiler opted to enable the
+ubsan check in the current basic block.
+
+Rules to allow ubsan checks are not part of the intrinsic declaration, and
+controlled by compiler options.
+
+This intrinsic is the ubsan specific version of ``@llvm.allow.runtime.check()``.
+
+Arguments:
+""""""""""
+
+An integer describing the kind of ubsan check guarded by the intrinsic.
+
+Semantics:
+""""""""""
+
+The intrinsic ``@llvm.allow.ubsan.check()`` returns either ``true`` or
+``false``, depending on compiler options. 
+
+For each evaluation of a call to this intrinsic, the program must be valid and
+correct both if it returns ``true`` and if it returns ``false``.
+
+When used in a branch condition, it allows us to choose between
+two alternative correct solutions for the same problem. 
+
+If the intrinsic is evaluated as ``true``, program must check ubsan condition,
+and report if needed. If the intrinsic is evaluated as ``false``, program must
+avoid checking ubsan condition and assume it passed.
+
+Example:
+
+.. code-block:: text
+
+    %allow = call i1 @llvm.allow.ubsan.check(i8 5)
+    %not.allow = xor i1 %allow, true
+    %cond = or i1 %ubcheck, %not.allow
+    br i1 %cond, label %cont, label %trap
+
+  cont:
+    ; Proceed
+
+  trap:
+    call void @llvm.ubsantrap(i8 5)
+    unreachable
+
+
+'``llvm.allow.runtime.check``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i1 @llvm.allow.runtime.check(metadata %kind)
+
+Overview:
+"""""""""
+
+This intrinsic returns ``true`` if and only if the compiler opted to enable
+runtime checks in the current basic block.
+
+Rules to allow runtime checks are not part of the intrinsic declaration, and
+controlled by compiler options.
+
+This intrinsic is non-ubsan specific version of ``@llvm.allow.ubsan.check()``.
+
+Arguments:
+""""""""""
+
+A string identifying the kind of runtime check guarded by the intrinsic. The
+string can be used to control rules to allow checks.
+
+Semantics:
+""""""""""
+
+The intrinsic ``@llvm.allow.ubsan.check()`` returns either ``true`` or
+``false``, depending on compiler options. 
+
+For each evaluation of a call to this intrinsic, the program must be valid and
+correct both if it returns ``true`` and if it returns ``false``.
+
+When used in a branch condition, it allows us to choose between
+two alternative correct solutions for the same problem. 
+
+If the intrinsic is evaluated as ``true``, program should execute a guarded
+checks. If the intrinsic is evaluated as ``false``, the program should avoid any
+unnecessary checks.
+
+Example:
+
+.. code-block:: text
+
+    %allow = call i1 @llvm.allow.runtime.check(metadata !"my_check")
+    br i1 %allow, label %fast_path, label %slow_path
+
+  fast_path:
+    ; Omit diagnostics.
+
+  slow_path:
+    ; Additional diagnostics.
+
 
 '``llvm.load.relative``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

llvm/include/llvm/IR/Intrinsics.td

@@ -1728,6 +1728,16 @@ def int_debugtrap : Intrinsic<[]>,
 def int_ubsantrap : Intrinsic<[], [llvm_i8_ty],
                               [IntrNoReturn, IntrCold, ImmArg<ArgIndex<0>>]>;
 
+// Return true if ubsan check is allowed.
+def int_allow_ubsan_check : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_i8_ty],
+    [IntrInaccessibleMemOnly, IntrWriteMem, ImmArg<ArgIndex<0>>, NoUndef<RetIndex>]>,
+    ClangBuiltin<"__builtin_allow_ubsan_check">;
+
+// Return true if runtime check is allowed.
+def int_allow_runtime_check : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_metadata_ty],
+    [IntrInaccessibleMemOnly, IntrWriteMem, NoUndef<RetIndex>]>,
+    ClangBuiltin<"__builtin_allow_runtime_check">;
+
 // Support for dynamic deoptimization (or de-specialization)
 def int_experimental_deoptimize : Intrinsic<[llvm_any_ty], [llvm_vararg_ty],
                                             [Throws]>;