[PATCH] D122248: [clang][CodeGen]Fix clang crash and add bitfield support in __builtin_dump_struct

[Wang Yihan via Phabricator via cfe-commits]

yihanaa added a comment.

In D122248#3403698 <https://reviews.llvm.org/D122248#3403698>, @erichkeane wrote:

>> I'm sorry I misunderstood what you meant @aaron.ballman.
>>
>> Can we follow the lead of LLVM IR？it use 'undef'
>> for example:
>>
>>   struct T6A {
>>       unsigned a : 1;
>>       unsigned  : 0;
>>       unsigned c : 1;
>>   };
>>   
>>   @__const.foo.a = private unnamed_addr constant %struct.T6A { i8 1, [3 x i8] undef, i8 1, [3 x i8] undef }, align 4
>
> I misunderstood him too, he told me off line :)
>
> I guess I would be 'ok' with `undef`, though that has a different meaning (it means, this has an arbitrary value).  In this case, it has NO value, which is somewhat different.

What if we don't emit '=' for zero-width bitfield, like this:

  struct Bar {
  unsigned c : 1;
  unsigned : 3;
  unsigned : 0;
  unsigned b;
  };
  
  struct Bar {
  unsigned int c : 1 = 0
  unsigned int   : 3 = 0
  unsigned int   : 0
  unsigned int b = 0
  }


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https://reviews.llvm.org/D122248