This document contains the release notes for the LLVM compiler
infrastructure, release 1.4. Here we describe the status of LLVM, including any
known problems and improvements from the previous release. The most up-to-date
version of this document can be found on the LLVM 1.4 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 the latest
release, please check out the main LLVM
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.
This is the fifth public release of the LLVM compiler infrastructure.
At this time, LLVM is known to correctly compile a broad range of
C and C++ programs, including the SPEC CPU95 & 2000 suite. This release
includes several major enhancements to the LLVM system, including a new
PowerPC JIT, enhancements to the C/C++ front-end to provide source line number
information in LLVM, a new compiler
driver, and several other enhancements listed below. It also includes
bug fixes for those problems found since the 1.3 release.
Note that this release seperates the LLVM Program Testsuite out of the
main LLVM distribution into a seperate CVS repository and tarball. This
reduces the size of the main LLVM distribution. Also note that LLVM now
builds tools into llvm/Debug/bin by default instead of llvm/tools/Debug.
LLVM is known to work on the following platforms:
- Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
other unix-like systems).
- Sun UltraSPARC workstations running Solaris 8.
- Intel and AMD machines running on Win32 with the Cygwin libraries (limited
support is available for native builds with Visual C++).
- PowerPC-based Mac OS X systems, running 10.2 and above.
The core LLVM infrastructure uses
GNU autoconf to adapt itself
to the machine and operating system on which it is built. However, minor
porting may be required to get LLVM to work on new platforms. We welcome your
portability patches and reports of successful builds or error messages.
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.
The following components of this LLVM release are either untested, known to
be broken or unreliable, or are in early development. These components should
not be relied on, and bugs should not be filed against them, but they may be
useful to some people. In particular, if you would like to work on one of these
components, please contact us on the llvmdev list.
- The following passes are incomplete or buggy, and may be removed in future
releases: -pgmdep, -memdep, -ipmodref, -cee, -branch-combine,
-instloops, -paths, -pre
- The llvm-db tool is in a very early stage of development, but can
be used to step through programs and inspect the stack.
- The "iterative scan" register allocator (enabled with -regalloc=iterativescan)
is not stable.
- Inline assembly is not yet supported.
- "long double" is transformed by the front-end into "double". There is no
support for floating point data types of any size other than 32 and 64
bits.
- The following Unix system functionality has not been tested and may not
work:
- sigsetjmp, siglongjmp - These are not turned into the
appropriate invoke/unwind instructions. Note that
setjmp and longjmp are compiled correctly.
- getcontext, setcontext, makecontext
- These functions have not been tested.
- Although many GCC extensions are supported, some are not. In particular,
the following extensions are known to not be supported:
- Local Labels: Labels local to a block.
- Nested Functions: As in Algol and Pascal, lexical scoping of functions.
- Constructing Calls: Dispatching a call to another function.
- Extended Asm: Assembler instructions with C expressions as operands.
- Constraints: Constraints for asm operands.
- Asm Labels: Specifying the assembler name to use for a C symbol.
- Explicit Reg Vars: Defining variables residing in specified registers.
- Vector Extensions: Using vector instructions through built-in functions.
- Target Builtins: Built-in functions specific to particular targets.
- Thread-Local: Per-thread variables.
- Pragmas: Pragmas accepted by GCC.
The following GCC extensions are partially supported. An ignored
attribute means that the LLVM compiler ignores the presence of the attribute,
but the code should still work. An unsupported attribute is one which is
ignored by the LLVM compiler and will cause a different interpretation of
the program.
- Variable Length:
Arrays whose length is computed at run time.
Supported, but allocated stack space is not freed until the function returns (noted above).
- Function Attributes:
Declaring that functions have no side effects or that they can never
return.
Supported: format, format_arg, non_null,
noreturn, constructor, destructor,
unused,
deprecated, warn_unused_result, weak
Ignored: noinline,
always_inline, pure, const, nothrow,
malloc, no_instrument_function, cdecl
Unsupported: used, section, alias,
visibility, regparm, stdcall,
fastcall, all other target specific attributes
- Variable Attributes:
Specifying attributes of variables.
Supported: cleanup, common, nocommon,
deprecated, transparent_union,
unused, weak
Unsupported: aligned, mode, packed,
section, shared, tls_model,
vector_size, dllimport,
dllexport, all target specific attributes.
- Type Attributes: Specifying attributes of types.
Supported: transparent_union, unused,
deprecated, may_alias
Unsupported: aligned, packed,
all target specific attributes.
- Other Builtins:
Other built-in functions.
We support all builtins which have a C language equivalent (e.g.,
__builtin_cos), __builtin_alloca,
__builtin_types_compatible_p, __builtin_choose_expr,
__builtin_constant_p, and __builtin_expect
(currently ignored). We also support builtins for ISO C99 floating
point comparison macros (e.g., __builtin_islessequal).
The following extensions are known to be supported:
- Labels as Values: Getting pointers to labels and computed gotos.
- Statement Exprs: Putting statements and declarations inside expressions.
- Typeof:
typeof
: referring to the type of an expression.
- Lvalues: Using
?:
, ",
" and casts in lvalues.
- Conditionals: Omitting the middle operand of a
?:
expression.
- Long Long: Double-word integers.
- Complex: Data types for complex numbers.
- Hex Floats:Hexadecimal floating-point constants.
- Zero Length: Zero-length arrays.
- Empty Structures: Structures with no members.
- Variadic Macros: Macros with a variable number of arguments.
- Escaped Newlines: Slightly looser rules for escaped newlines.
- Subscripting: Any array can be subscripted, even if not an lvalue.
- Pointer Arith: Arithmetic on
void
-pointers and function pointers.
- Initializers: Non-constant initializers.
- Compound Literals: Compound literals give structures, unions,
or arrays as values.
- Designated Inits: Labeling elements of initializers.
- Cast to Union: Casting to union type from any member of the union.
- Case Ranges: `case 1 ... 9' and such.
- Mixed Declarations: Mixing declarations and code.
- Function Prototypes: Prototype declarations and old-style definitions.
- C++ Comments: C++ comments are recognized.
- Dollar Signs: Dollar sign is allowed in identifiers.
- Character Escapes:
\e
stands for the character <ESC>.
- Alignment: Inquiring about the alignment of a type or variable.
- Inline: Defining inline functions (as fast as macros).
- Alternate Keywords:
__const__
, __asm__
, etc., for header files.
- Incomplete Enums:
enum foo;
, with details to follow.
- Function Names: Printable strings which are the name of the current function.
- Return Address: Getting the return or frame address of a function.
- Unnamed Fields: Unnamed struct/union fields within structs/unions.
- Attribute Syntax: Formal syntax for attributes.
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).
For this release, the C++ front-end is considered to be fully
tested and works for a number of non-trivial programs, including LLVM
itself.
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.