LLVM 1.1 Release Notes
  1. Introduction
  2. What's New?
  3. Portability and Supported Platforms
  4. Installation Instructions
  5. Known Problems
  6. Additional Information

Written by the LLVM team


This document contains the release notes for the LLVM compiler infrastructure, release 1.1. Here we describe the status of LLVM, including any known problems and bug fixes from the previous release. The most up-to-date version of this document can be found on the LLVM 1.1 web site. If you are not reading this on the LLVM web pages, you should probably go there because this document may be updated after the release.

For more information about LLVM, including information about potentially more current releases, please check out the main web site. If you have questions or comments, the LLVM developer's mailing list is a good place to send them.

Note that if you are reading this file from CVS, this document applies to the next release, not the current one. To see the release notes for the current or previous releases, see the releases page.

What's New?

This is the second public release of the LLVM compiler infrastructure. This release is primarily a bugfix release, dramatically improving the C/C++ front-end and improving support for C++ in the LLVM core. This release also includes a few new features, such as a simple profiler, support for Mac OS X, better interoperability with external source bases, a new example language front-end, and improvements in a few optimizations. The performance of several LLVM components has been improved, and several gratuitous type-safety issues in the C front-end have been fixed.

At this time, LLVM is known to correctly compile and run all non-unwinding C & C++ SPEC CPU2000 benchmarks, the Olden benchmarks, and the Ptrdist benchmarks. It has also been used to compile many other programs. LLVM now also works with a broad variety of C++ programs, though it has still received much less testing than the C front-end.

The LLVM native code generators are very stable but do not currently support unwinding (exception throwing or longjmping), which prevent them from working with programs like the 253.perlbmk in SPEC CPU2000. The C backend and the rest of LLVM supports these programs, so you can still use LLVM with them. Support for unwinding will be added in a future release.

This release implements the following new features:
  1. A new LLVM profiler, similar to gprof, is available.
  2. LLVM and the C/C++ front-end now compile on Mac OS X! Mac OS X users can now explore the LLVM optimizer with the C backend and interpreter. Note that LLVM requires GCC 3.3 on Mac OS X.
  3. LLVM has been moved into an 'llvm' C++ namespace for easier integration with third-party code. Note that due to lack of namespace support in GDB 5.x, you will probably want to upgrade to GDB 6 or better to debug LLVM code.
  4. The build system now copies Makefiles dynamically from the source tree to the object tree as subdirectories are built. This means that:
    1. New directories can be added to the source tree, and the build will automatically pick them up (i.e. no need to edit configure.ac and re-run configure).
    2. You will need to build LLVM from the top of the object tree once to ensure that all of the Makefiles are copied into the object tree subdirectories.
  5. A front-end for "Stacker" (a simple Forth-like language) is now included in the main LLVM tree. Additionally, Reid Spencer, the author, contributed a document describing his experiences writing Stacker and the language itself. This document is invaluable for others writing front-ends targetting LLVM.
  6. The configure script will now configure all projects placed in the llvm/projects directory.
  7. The -tailcallelim pass can now introduce "accumulator" variables to transform functions in many common cases that it could not before.
  8. The -licm pass can now sink instructions out the bottom of loops in addition to being able to hoist them out the top.
  9. The -basicaa pass (the default alias analysis pass) has been upgraded to be significantly more precise.
  10. LLVM 1.1 implements a simple size optimization for LLVM bytecode files. This means that the 1.1 files are smaller than 1.0, but LLVM 1.0 won't read 1.1 bytecode files.
  11. The gccld program produces a runner script that includes command-line options to load the necessary shared objects.
In this release, the following missing features were implemented:
  1. The interpreter does not support invoke or unwind
  2. Interpreter does not support the vaarg instruction
  3. llvm-nm cannot read archive files
  4. Interpreter does not handle setne constant expression
In this release, the following Quality of Implementation issues were fixed:
  1. The C++ front-end now compiles functions to use the linkonce linkage type more, giving the optimizer more freedom.
  2. The C front-end now generates type-safe code in several cases that it did not before, allowing optimization of code that could not be optimized previously.
  3. The LLVM build system has been taught to catch some common configuration problems that caused it to get horribly confused.
  4. The LLVM header files are now -Wold-style-cast clean.
  5. The LLVM bytecode reader has been sped up a lot (up to 4x in some cases).
  6. In C++, methods and functions in anonymous namespaces now get internal linkage.
  7. Constant initializers now generate loops instead of potentially huge amounts of straight-line code.
  8. Code for running C++ destructors is now properly shared when possible. Before, the C++ front-end generated N^2 amounts of duplicated cleanup code in some cases.
  9. The JIT used to generate code for all functions pointed to by globals before the program started execution. Now, it waits until the first time the functions are called to compile them. This dramatically speeds up short runs of large C++ programs, which often have large numbers of functions pointed to by vtables.
In this release, the following bugs in the previous release were fixed:

Bugs in the LLVM Core:

  1. [inliner] Inlining invoke with PHI in unwind target is broken
  2. [linker] linkonce globals should link successfully to external globals
  3. [constmerge] Constant merging pass merges constants with external linkage
  4. [scalarrepl] Scalar Replacement of aggregates is decimating structures it shouldn't be
  5. [instcombine] Resolving invoke inserts cast after terminator
  6. llvm-as crashes when labels are used in phi nodes
  7. [build problem] Callgraph.cpp not pulled in from libipa.a
  8. Variables in scope of output setjmp calls should be volatile (Note that this does not affect correctness on many platforms, such as X86).
  9. [X86] Emission of global bool initializers broken
  10. [gccld] The -r (relinking) option does not work correctly
  11. [bcreader] Cannot read shift constant expressions from bytecode file
  12. [lowersetjmp] Lowersetjmp pass breaks dominance properties!
  13. SymbolTable::getUniqueName is very inefficient
  14. bugpoint must not pass -R<directory> to Mach-O linker
  15. [buildscripts] Building into objdir with .o in it fails
  16. [setjmp/longjmp] Linking C programs which use setjmp/longjmp sometimes fail with references to the C++ runtime library!
  17. AsmParser Misses Symbol Redefinition Error
  18. gccld -Lfoo -lfoo fails to find ./foo/libfoo.a
  19. [bcreader] Incorrect cast causes misread forward constant references
  20. [adce] ADCE considers blocks without postdominators to be unreachable
  21. [X86] div and rem constant exprs invalidate iterators!
  22. [vmcore] Symbol table doesn't rename colliding variables during type resolution
  23. Archive reader does not understand 4.4BSD/Mac OS X long filenames
  24. [llvm-ar] Command line arguments have funny syntax

Bugs in the C/C++ front-end:

  1. C++ frontend can crash when compiling virtual base classes
  2. C backend fails on constant cast expr to ptr-to-anonymous struct
  3. #ident is not recognized by C frontend
  4. C front-end miscompiles the builtin_expect intrinsic!
  5. 1.0 precompiled libstdc++ does not include wchar_t support
  6. llvmgcc asserts when compiling functions renamed with asm's
  7. C frontend crashes on some programs with lots of types.
  8. llvm-gcc crashes compiling global union initializer
  9. C front-end crash on empty structure
  10. CFrontend crashes when compiling C99 compound expressions
  11. llvm-gcc infinite loops on "case MAXINT:"
  12. [C++] Catch blocks make unparsable labels
  13. [C++] Initializing array with constructible objects fail
  14. llvm-gcc tries to add bools
  15. [c++] C++ Frontend lays out superclasses like anonymous bitfields!
  16. C front-end miscompiles unsigned enums whose LLVM types are signed
  17. Casting a string constant to void crashes llvm-gcc
  18. [llvmg++] Enum types are incorrectly shrunk to smaller than 'int' size
  19. [llvmg++] Cannot use pointer to member to initialize global
  20. [llvm-gcc] ?: operator as lvalue not implemented
  21. [C/C++] Bogus warning about taking the address of 'register' variable
  22. crash assigning into an array in a struct which contains a bitfield.
  23. Oversized integer bitfields cause crash
  24. [llvm-gcc] Bitfields & large array don't mix well
  25. [llvm-gcc] Complex division is not supported
  26. [llvm-gcc] Illegal union field reference
  27. [llvmg++] Front-end attempts to return structure by value
  28. [llvmg++] Pointer to member initializers not supported in constructors
  29. [llvm-gcc] crash on union initialization
  30. [llvm-g++] ?: expressions do not run correct number of destructors!
  31. [llvm-gcc] Pointer & constant results in invalid shift
  32. [llvmg++] call through array of pointers to member functions causes assertion
Portability and Supported Platforms

LLVM has been extensively tested on Intel and AMD machines running Red Hat Linux and has been tested on Sun UltraSPARC workstations running Solaris 8. Additionally, LLVM works on Mac OS X 10.3 and above, but only with the C backend or interpreter (no native backend for the PowerPC is available yet).

NOTE: You may have to reset the LLVMGCCDIR variable in your Makefile.config to use the target triplet powerpc-apple-darwin7.0.0 instead of whatever configure detected; otherwise you will get errors trying to build crtend. This is fixed in 1.2.

The core LLVM infrastructure uses "autoconf" for portability, so hopefully we work on more platforms than that. However, it is likely that we missed something and that minor porting is required to get LLVM to work on new platforms. We welcome portability patches and error messages.

Known Problems

This section contains all known problems with the LLVM system, listed by component. As new problems are discovered, they will be added to these sections. If you run into a problem, please check the LLVM bug database and submit a bug if there isn't already one.

Known problems with the LLVM Core
Bugs in 1.1 fixed in 1.2:
Known problems with the C front-end
Bugs in 1.1 fixed in 1.2:
  • [llvm-gcc] miscompilation of 'X = Y = Z' with aggregate values
  • [llvmgcc] Structure copies result in a LOT of code
  • [llvmgcc] Invalid code created for complex division operation
  • [llvmgcc] Incorrect code generation for pointer subtraction
  • [llvmg++] Crash assigning pointers-to-members with casted types
  • [llvm-g++] Cleanups and gotos don't mix properly
  • [llvmgcc] Crash on auto register variable with specific register specified
  • Notes

    If you run into GCC extensions which have not been included in any of these lists, please let us know (also including whether or not they work).

    Known problems with the C++ front-end

    For this release, the C++ front-end is considered to be fully functional but has not been tested as thoroughly as the C front-end. It has been tested and works for a number of non-trivial programs, but there may be lurking bugs. Please report any bugs or problems.

    Bugs in 1.1 fixed in 1.2:
    Known problems with the X86 back-end
    Bugs in 1.1 fixed in 1.2:
    Known problems with the Sparc back-end
    Bugs in 1.1 fixed in 1.2:
    Known problems with the C back-end
    Additional Information

    A wide variety of additional information is available on the LLVM web page, including mailing lists and publications describing algorithms and components implemented in LLVM. The web page also contains versions of the API documentation which is up-to-date with the CVS version of the source code. You can access versions of these documents specific to this release by going into the "llvm/doc/" directory in the LLVM tree.

    If you have any questions or comments about LLVM, please feel free to contact us via the mailing lists.

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