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This fixes PR32471. As comment 10 on that bug report highlights (https://bugs.llvm.org//show_bug.cgi?id=32471#c10), there are quite a few different defendable design tradeoffs that could be made, including not representing pointers at all in LLT. I decided to go for representing vector-of-pointer as a concept in LLT, while keeping the size of the LLT type 64 bits (this is an increase from 48 bits before). My rationale for keeping pointers explicit is that on some targets probably it's very handy to have the distinction between pointer and non-pointer (e.g. 68K has a different register bank for pointers IIRC). If we keep a scalar pointer, it probably is easiest to also have a vector-of-pointers to keep LLT relatively conceptually clean and orthogonal, while we don't have a very strong reason to break that orthogonality. Once we gain more experience on the use of LLT, we can of course reconsider this direction. Rejecting vector-of-pointer types in the IRTranslator is also an option to avoid the crash reported in PR32471, but that is only a very short-term solution; also needs quite a bit of code tweaks in places, and is probably fragile. Therefore I didn't consider this the best option. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300664 91177308-0d34-0410-b5e6-96231b3b80d8
Design Of lib/System
====================
The software in this directory is designed to completely shield LLVM from any
and all operating system specific functionality. It is not intended to be a
complete operating system wrapper (such as ACE), but only to provide the
functionality necessary to support LLVM.
The software located here, of necessity, has very specific and stringent design
rules. Violation of these rules means that cracks in the shield could form and
the primary goal of the library is defeated. By consistently using this library,
LLVM becomes more easily ported to new platforms since the only thing requiring
porting is this library.
Complete documentation for the library can be found in the file:
llvm/docs/SystemLibrary.html
or at this URL:
http://llvm.org/docs/SystemLibrary.html
While we recommend that you read the more detailed documentation, for the
impatient, here's a high level summary of the library's requirements.
1. No system header files are to be exposed through the interface.
2. Std C++ and Std C header files are okay to be exposed through the interface.
3. No exposed system-specific functions.
4. No exposed system-specific data.
5. Data in lib/System classes must use only simple C++ intrinsic types.
6. Errors are handled by returning "true" and setting an optional std::string
7. Library must not throw any exceptions, period.
8. Interface functions must not have throw() specifications.
9. No duplicate function impementations are permitted within an operating
system class.
To accomplish these requirements, the library has numerous design criteria that
must be satisfied. Here's a high level summary of the library's design criteria:
1. No unused functionality (only what LLVM needs)
2. High-Level Interfaces
3. Use Opaque Classes
4. Common Implementations
5. Multiple Implementations
6. Minimize Memory Allocation
7. No Virtual Methods