[lldb-dev] Question about IRForTarget
zturner at google.com
Mon Mar 16 10:45:20 PDT 2015
So assuming the correct type is passed today, is that semantically
equivalent to passing nullptr today? Because if not, then I would have
expected a test to fail somewhere. Not because an assertion fired, but
because something somewhere had the wrong idea about a type.
On Mon, Mar 16, 2015 at 10:43 AM David Blaikie <blaikie at google.com> wrote:
> On Mon, Mar 16, 2015 at 10:39 AM, Zachary Turner <zturner at google.com>
>> Hi Sean,
>> A change went in over the weekend to change the
>> way GetElementPtrInst::Create works. Now, for pointer types, you need to
>> manually specify the type of the pointee, as pointerType->getType() won't
>> work anymore. This broke the build, so a workaround was employed to simply
>> pass nullptr for this argument. But this is likely to be incorrect, and
>> instead we need the actual llvm::Type for the pointee. I've looked over
>> the code, and I *think* that on line 2209 we can replace the nullptr with
>> old_constant->getType(), and on line 2396 we can place the nullptr with
>> What are your thoughts here?
>> Secondly, the change to nullptr does not seem to have caused any test
> This is expected - for now, nullptr is an acceptable value. The assertion
> I have in GetElementPtrInst's ctor is:
> assert(!PointeeType || PointeeType == getSourceElementType());
> Eventually I'll need to remove the nullptr case once I believe I've
> flushed out all the callers - this will verify that the callers are passing
> the type that matches the pointee type of the pointer operand. (at this
> point the current lldb code will assert-fail, if it is tested) You can try
> removing the first part of that assert locally to see if the LLDB code path
> is tested currently.
> Once similar changes have been applied to all pointer-element-type-aware
> uses of pointers in LLVM IR, I'll start trying to remove the ability to
> query a pointer type for its element type.
>> Is there any way we can add some tests for this? If this is not
>> something that is testable through the public interface, I recently added
>> gtest unit tests to the build. It's not enabled in the Xcode build (but
>> will be soon), but if you tell me how to set up a test, call the right
>> function, and what outputs to expect, I can write it.
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