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In r143502, we renamed getHostTriple() to getDefaultTargetTriple() as part of work to allow the user to supply a different default target triple at configure time. This change also affected the JIT. However, it is inappropriate to use the default target triple in the JIT in most circumstances because this will not necessarily match the current architecture used by the process, leading to illegal instruction and other such errors at run time. Introduce the getProcessTriple() function for use in the JIT and its clients, and cause the JIT to use it. On architectures with a single bitness, the host and process triples are identical. On other architectures, the host triple represents the architecture of the host CPU, while the process triple represents the architecture used by the host CPU to interpret machine code within the current process. For example, when executing 32-bit code on a 64-bit Linux machine, the host triple may be 'x86_64-unknown-linux-gnu', while the process triple may be 'i386-unknown-linux-gnu'. This fixes JIT for the 32-on-64-bit (and vice versa) build on non-Apple platforms. Differential Revision: http://llvm-reviews.chandlerc.com/D254 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172627 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