[Lldb-commits] [PATCH] D145580: [lldb] Show register fields using bitfield struct types

[David Spickett via Phabricator via lldb-commits]

DavidSpickett added inline comments.


================
Comment at: lldb/source/Core/DumpRegisterValue.cpp:136-137
+  // See if we have made this type before and can reuse it.
+  CompilerType fields_type = ast->GetTypeForIdentifier<clang::CXXRecordDecl>(
+      ConstString(register_type_name.c_str()));
+
----------------
aprantl wrote:
> DavidSpickett wrote:
> > aprantl wrote:
> > > bulbazord wrote:
> > > > This seems highly specific to C++... Let's try to find another way to do this, ideally with `TypeSystem` instead of `TypeSystemClang` and `clang::CXXRecordDecl`.
> > > Are we saving a lot of code by going through the clang typesystem here, or would walking the bits and formatting the directly be roughly the same amount of code?
> > Funny you should mention that.
> > 
> > I was initially doing that, but in the RFC it was suggested I use the existing printers for C types (https://discourse.llvm.org/t/rfc-showing-register-fields-in-lldb/64676/2). There's also a hint that this would make assigning to specific fields more easy (though that is a very far off goal).
> > 
> > This is what the first version looked like:
> > ```
> > (lldb) register read cpsr
> >     cpsr = 0x60001000
> > | N | Z | C | V | TCO | DIT | UAO | PAN | SS | IL | SSBS | BTYPE | D | A | I | F | nRW | EL | SP |
> > | 0 | 1 | 1 | 0 |  0  |  0  |  0  |  0  | 0  | 0  |  1   |   0   | 0 | 0 | 0 | 0 |  0  | 0  | 0  |
> > ```
> > Of course it would be refined based on line length and field size etc etc. A lot of the things the type printers already do, which is why using them looked like it would save some effort.
> > 
> > Some of that extra formatting code will get written anyway because I want to eventually add a register command that will show you the register layout. So table formatting is needed either way. That would produce something like:
> > ```
> > (lldb) register info cpsr
> > | 31 | 30 | ...
> > | N  |  Z | ...
> > ```
> > 
> > So overall no there's nothing preventing me from walking the bits. Assuming you already have code to format text tables nicely, it would be about the same amount of code.
> > 
> > I need to check if we have any generic table formatting code, or could extract some from somewhere.
> Sorry I wasn't aware of the history :-)
Do you have an idea of how much work it would be to make TypeSystem do the same things TypeSystemClang does? Maybe more to the point, would I be trying to make TypeSystem do something it just isn't designed to do.


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https://reviews.llvm.org/D145580