[all-commits] [llvm/llvm-project] e294ec: BPF: fix enum value 0 issue for __builtin_preserve...

[yonghong-song via All-commits]

  Branch: refs/heads/release/12.x
  Home:   https://github.com/llvm/llvm-project
  Commit: e294ece42d85191875782ed05cb607451f493944
      https://github.com/llvm/llvm-project/commit/e294ece42d85191875782ed05cb607451f493944
  Author: Yonghong Song <yhs at fb.com>
  Date:   2021-05-03 (Mon, 03 May 2021)

  Changed paths:
    M clang/lib/Sema/SemaChecking.cpp
    M clang/test/CodeGen/builtins-bpf-preserve-field-info-4.c

  Log Message:
  -----------
  BPF: fix enum value 0 issue for __builtin_preserve_enum_value()

Lorenz Bauer reported that the following code will have
compilation error for bpf target:
    enum e { TWO };
    bpf_core_enum_value_exists(enum e, TWO);
The clang emitted the following error message:
    __builtin_preserve_enum_value argument 1 invalid

In SemaChecking, an expression like "*(enum NAME)1" will have
cast kind CK_IntegralToPointer, but "*(enum NAME)0" will have
cast kind CK_NullToPointer. Current implementation only permits
CK_IntegralToPointer, missing enum value 0 case.

This patch permits CK_NullToPointer cast kind and
the above test case can pass now.

Differential Revision: https://reviews.llvm.org/D97659

(cherry picked from commit 283db5f0837d55f91242812003adf6e189ba743e)