[cfe-dev] Crash on conditional operation with address_space pointer

[John McCall via cfe-dev]

> On Aug 3, 2018, at 8:05 PM, Leonard Chan <leonardchan at google.com> wrote:
> Oh I see. I misinterpreted a few things. I'll change the patch to
> print something from err_typecheck_incompatible_address_space instead
> in addition to raising the warning.

Great, please CC me on the review when you put it up.

John.

> On Fri, Aug 3, 2018 at 4:57 PM John McCall <rjmccall at apple.com> wrote:
>> 
>>> On Aug 3, 2018, at 7:56 PM, Leonard Chan <leonardchan at google.com> wrote:
>>> Oh. Should an error be printed here instead, or it's fine to let it
>>> crash I suppose since the code shouldn't be generate in the first
>>> place?
>>> 
>>> It seems that at least 3 tests expect this conditional operator to
>>> print a "pointer type mismatch" warning.
>> 
>> The compiler should definitely never crash.  That sounds like the right diagnostic
>> we should be emitting, except I don't think it can be just a warning for an
>> address-space mismatch.
>> 
>> John.
>> 
>>> On Fri, Aug 3, 2018 at 4:50 PM John McCall <rjmccall at apple.com> wrote:
>>>> 
>>>>> On Aug 3, 2018, at 7:42 PM, Leonard Chan <leonardchan at google.com> wrote:
>>>>> Does this mean the check during the BitCast codegen shouldn't be there
>>>>> in the first place?
>>>> 
>>>> We should not be generating code for this program, correct.
>>>> 
>>>> John.
>>>> 
>>>>> On Fri, Aug 3, 2018 at 4:28 PM John McCall <rjmccall at apple.com> wrote:
>>>>>> 
>>>>>>> On Aug 3, 2018, at 7:03 PM, Leonard Chan via cfe-dev <cfe-dev at lists.llvm.org> wrote:
>>>>>>> Compiling the following causes clang to crash
>>>>>>> 
>>>>>>> char *cmp(__attribute__((address_space(1))) char *x,
>>>>>>> __attribute__((address_space(2))) char *y) {
>>>>>>> return x < y ? x : y;
>>>>>>> }
>>>>>>> 
>>>>>>> with the message: "wrong cast for pointers in different address
>>>>>>> spaces(must be an address space cast)!"
>>>>>>> 
>>>>>>> The problem seems to be that BitCast is used when
>>>>>>> AddressSpaceConversion should be used instead when casting the `y` to
>>>>>>> a void *. The error is thrown during code gen where a BitCast expects
>>>>>>> the source and dest address space to be the same.
>>>>>>> 
>>>>>>> I submitted a patch (https://reviews.llvm.org/D50278) for a fix where
>>>>>>> we check for differing address spaces in the operands and perform an
>>>>>>> AddressSpaceConversion cast if anyone wants to review it. It seems
>>>>>>> that AddressSpaceConversions though were only available when using
>>>>>>> OpenCL. I'm not familiar with OpenCL and not sure if this was
>>>>>>> intended, but it fixes the crash while still retaining the warning of
>>>>>>> using mismatched pointers and all the clang tests pass.
>>>>>> 
>>>>>> If address spaces 1 and 2 don't overlap — and absent target-specific
>>>>>> information, the assumption is that they don't — then neither the comparison
>>>>>> nor the conditional operator here should type-check.
>>>>>> 
>>>>>> John.
>>>> 
>>