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f38cc38fa6
This patch provides basic support for powerpc64le as an LLVM target. However, use of this target will not actually generate little-endian code. Instead, use of the target will cause the correct little-endian built-in defines to be generated, so that code that tests for __LITTLE_ENDIAN__, for example, will be correctly parsed for syntax-only testing. Code generation will otherwise be the same as powerpc64 (big-endian), for now. The patch leaves open the possibility of creating a little-endian PowerPC64 back end, but there is no immediate intent to create such a thing. The LLVM portions of this patch simply add ppc64le coverage everywhere that ppc64 coverage currently exists. There is nothing of any import worth testing until such time as little-endian code generation is implemented. In the corresponding Clang patch, there is a new test case variant to ensure that correct built-in defines for little-endian code are generated. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187179 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