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e2b7b29a82
Final commit for this bug. This removes the last EH holdouts in LLVM
and turns off exception support by using the -fno-exceptions option. This
leads to the following reduction in library and executable sizes:
DEBUG BUILD RELEASE BUILD
before after delta before after delta
lib 162,328K 157,616K 4,712 17,864K 16,416K 1,448K
bin 571,444K 557,156K 14,288 63,296K 56,996K 6,300K
Debug Improvement: 19,000K (2.59%)
Release Improvement: 7,748K (9.55%)
llvm-svn: 29882
44 lines
1.9 KiB
Plaintext
44 lines
1.9 KiB
Plaintext
Design Of lib/System
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====================
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The software in this directory is designed to completely shield LLVM from any
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and all operating system specific functionality. It is not intended to be a
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complete operating system wrapper (such as ACE), but only to provide the
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functionality necessary to support LLVM.
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The software located here, of necessity, has very specific and stringent design
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rules. Violation of these rules means that cracks in the shield could form and
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the primary goal of the library is defeated. By consistently using this library,
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LLVM becomes more easily ported to new platforms since the only thing requiring
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porting is this library.
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Complete documentation for the library can be found in the file:
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llvm/docs/SystemLibrary.html
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or at this URL:
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http://llvm.org/docs/SystemLibrary.html
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While we recommend that you read the more detailed documentation, for the
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impatient, here's a high level summary of the library's requirements.
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1. No system header files are to be exposed through the interface.
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2. Std C++ and Std C header files are okay to be exposed through the interface.
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3. No exposed system-specific functions.
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4. No exposed system-specific data.
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5. Data in lib/System classes must use only simple C++ intrinsic types.
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6. Errors are handled by returning "true" and setting an optional std::string
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7. Library must not throw any exceptions, period.
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8. Interface functions must not have throw() specifications.
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9. No duplicate function impementations are permitted within an operating
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system class.
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To accomplish these requirements, the library has numerous design criteria that
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must be satisfied. Here's a high level summary of the library's design criteria:
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1. No unused functionality (only what LLVM needs)
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2. High-Level Interfaces
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3. Use Opaque Classes
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4. Common Implementations</a></li>
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5. Multiple Implementations</a></li>
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6. Minimize Memory Allocation</a></li>
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7. No Virtual Methods
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