-
-
- LLVM now includes an - Interprocedural Sparse Conditional Constant Propagation pass, named - -ipsccp, which is run by default at link-time. -
- LLVM 1.5 is now about 15% faster than LLVM 1.4 and its core data structures - use about 30% less memory. -
- LLVM includes new experimental native code generators for SparcV8 and - Alpha. -
- Support for Microsoft Visual Studio is improved, and now documented. -
LLVM 1.7 includes a brand new llvm-gcc, based on GCC 4.0.1. This version +of llvm-gcc solves many serious long-standing problems with llvm-gcc, including +all of those blocked by the llvm-gcc 4 meta +bug. In addition, llvm-gcc4 implements support for many new features, +including GCC inline assembly, generic vector support, SSE and Altivec +intrinsics, and several new GCC attributes. Finally, llvm-gcc4 is +significantly faster than llvm-gcc3, respects -O options, its -c/-S options +correspond to GCC's (they emit native code), supports Objective C/C++, and +it has debugging support well underway.
+If you can use it, llvm-gcc4 offers significant new functionality, and we +hope that it will replace llvm-gcc3 completely in a future release. +Unfortunately, it does not currently support C++ exception handling at all, and +it only works on Apple Mac OS/X machines with X86 or PowerPC processors. +
- --
-
-
The LLVM IR and llvm-gcc4 front-end now fully support arbitrary GCC inline assembly. The LLVM X86 and PowerPC +code generators have initial support for it, +being able to compile basic statements, but are missing some features. Please +report any inline asm statements that crash the compiler or that are miscompiled +as bugs.
-
-
- Building LLVM in optimized mode - should no longer cause GCC to hit swap in the PowerPC backend. -
LLVM 1.7 includes a new, fully functional, SPARC backend built in the +target-independent code generator. This SPARC backend includes support for +SPARC V8 and SPARC V9 subtargets (controlling whether V9 features can be used), +and targets the 32-bit SPARC ABI.
+ +The LLVM 1.7 release is the last release that will include the LLVM "SparcV9" +backend, which was the very first LLVM native code generator. It will +be removed in LLVM 1.8, being replaced with the new SPARC backend.
+LLVM now includes significantly extended support for SIMD vectors in its +core instruction set. It now includes three new instructions for manipulating +vectors: extractelement, +insertelement, and +shufflevector. Further, +many bugs in vector handling have been fixed, and vectors are now supported by +the target-independent code generator. For example, if a vector operation is +not supported by a particular target, it will be correctly broken down and +executed as scalar operations.
+ +Because llvm-gcc3 does not support GCC generic vectors or vector intrinsics, +llvm-gcc4 must be used.
-
-
-
The LLVM X86 backend now supports Intel SSE 1, 2, and 3, and now uses scalar +SSE operations to implement scalar floating point math when the target supports +SSE1 (for floats) or SSE2 (for doubles). Vector SSE instructions are generated +by llvm-gcc4 when the generic vector mechanism or specific SSE intrinsics are +used. +
+ +The LLVM PowerPC backend now supports the Altivec instruction set, including +both GCC -maltivec and -faltivec modes. Altivec instructions are generated +by llvm-gcc4 when the generic vector mechanism or specific Altivec intrinsics +are used. +
+-
+
- The Loop Unswitching pass (-loop-unswitch) has had several bugs + fixed, has several new features, and is enabled by default in llvmgcc3 + now. +
- The Loop Strength Reduction pass (-loop-reduce) is now enabled for + the X86 and Alpha backends. +
- The Instruction Combining pass (-instcombine) now includes a + framework and implementation for simplifying code based on whether computed + bits are demanded or not. +
- The Scalar Replacement of Aggregates pass (-scalarrepl) can now + promote simple unions to registers. +
- The Reassociation pass (-reassociate) can now + factor expressions, e.g. turning "A*A+A*B" into "A*(A+B)". +
- Several LLVM passes are significantly +faster. +
-
+
- LLVM has a new prepass (before register allocation) list scheduler, which + supports bottom-up and top-down scheduling, pluggable priority functions and + pluggable hazard recognizers. The X86 backend uses this to reduce register + pressure and RISC targets schedule based on operation latency. +
- The tblgen-based target description framework introduced in LLVM 1.6 has + several new features, useful for targets that can fold loads and stores into + operations, and features that make the .td files more expressive. +
- The instruction selector is significantly faster in 1.7 than in 1.6. +
- The X86, Alpha and Itanium backends use new DAG-DAG instruction selectors, + making them easier to maintain and generate slightly better code. +
- The X86 backend now supports generation of Scalar SSE code for scalar FP + expressions. LLVM provides significantly better performance with Scalar SSE + instructions than it does with the Intel floating point stack + instructions. +
- The Itanium backend now has a bundling pass, which improves performance + by ~10% and reduces code size (previously it unconditionally inserted a stop + bit after every instruction). +
Bugs fixed in the LLVM Core:
- +-
+
- The Mac OS/X PowerPC and X86 backends now have initial support for + Darwin DWARF + debugging information, however, debug info generation has been disabled for + the 1.7 release in llvmgcc4. +
- LLVM includes the new + llvm-config utility, which makes it easier to build and link programs + against the LLVM libraries when not using the LLVM makefiles. +
- LLVM now supports first class global ctor/dtor initialization lists, no + longer forcing targets to use "__main". +
- LLVM supports assigning globals and functions to a particular section + in the result executable using the GCC section attribute. +
- Adding intrinsics to LLVM is now + significantly easier. +
- llvmgcc4 now fully supports C99 Variable Length Arrays, including dynamic + stack deallocation. -
Code Generator Bugs:
- +Bugs in the C/C++ front-end:
--
-
- [llvmgcc] llvm-gcc incorrectly - rejects some constant initializers involving the addresses of array - elements -
- [llvm-g++] Crash compiling - anonymous union -
- [llvm-g++] Do not use dynamic - initialization where static init will do -
- [llvmgcc] Field offset - miscalculated for some structure fields following bit fields -
-
+
- The official LLVM URL is now + http://llvm.org/. +
- The LLVM intrinsics used to be overloaded based on type: for example, + llvm.ctpop could work with any + integer datatype. They are now separated into different intrinsics with + suffixes to denote their argument type (e.g. llvm.ctpop.i32)). Old + LLVM .ll and .bc files that use these intrinsics will continue to work with + new LLVM versions (they are transparently upgraded by the parsers), but will + cause a warning to be emitted. +
- The llvm.readport, llvm.writeport, llvm.readio, + and llvm.writeio intrinsics have been removed. The first two + were ever only supported by the X86 backend, the last two were never + correctly supported by any target, and none were accessible through the + C front-end. Inline assembly support can now be used to + implement these operations. +
- The llvm-db tool had basic support for stepping through code, which + used the JIT. This code has been removed, and DWARF emission support added + instead. llvm-db still exists in CVS if someone wanted to write a + ptrace backend for it. +
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). +
- Intel and AMD machines running Red Hat Linux, Fedora Core 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. +
- PowerPC and X86-based Mac OS X systems, running 10.2 and above. +
- Alpha-based machines running Debian GNU/Linux. +
- Itanium-based machines running Linux and HP-UX.
The core LLVM infrastructure uses @@ -204,7 +316,7 @@ 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 +href="http://llvm.org/bugs/">LLVM bug database and submit a bug if there isn't already one.
-
-
- The following passes are incomplete or buggy, and may be removed in future - releases: -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. -
- The SparcV8 and Alpha ports are experimental. +
- The -cee pass is known to be buggy, and may be removed in in a + future release. +
- The IA64 code generator is experimental. +
- The Alpha JIT is experimental. +
- "-filetype=asm" (the default) is the only supported value for the + -filetype llc option.
-
+
- none yet +
-
-
- In the JIT, dlsym on a symbol compiled by the JIT will not work. - -
- The JIT does not use mutexes to protect its internal data structures. As - such, execution of a threaded program could cause these data structures to be - corrupted. - -
- The lower-invoke pass does not - mark values live across a setjmp as volatile. This missing feature - only affects targets whose setjmp/longjmp libraries do not save and restore - the entire register file. +
- In the JIT, dlsym() on a symbol compiled by the JIT will not + work.
+llvm-gcc3 has many significant problems that are fixed by llvm-gcc4. See + those blocked on the llvm-gcc4 meta bug. +Two major ones include:
+-
-
- C99 Variable sized arrays do not release stack memory when they go out of +
- With llvm-gcc3,
+ C99 variable sized arrays do not release stack memory when they go out of
scope. Thus, the following program may run out of stack space:
for (i = 0; i != 1000000; ++i) { @@ -274,8 +397,8 @@ components, please contact us on the llvmdev list. }
- - Initialization of global union variables can only be done with the largest union member. +
- With llvm-gcc3, Initialization of global union variables can only be done with the largest union member.
-
-
- 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. @@ -339,14 +460,14 @@ work: Supported: format, format_arg, non_null, noreturn, constructor, destructor, - unused, + unused, used, deprecated, warn_unused_result, weak
- The C++ front-end inherits all problems afflicting the C front-end. -
- IA-64 specific: The C++ front-end does not use IA64 ABI compliant layout of v-tables. -In particular, it just stores function pointers instead of function -descriptors in the vtable. This bug prevents mixing C++ code compiled with -LLVM with C++ objects compiled by other C++ compilers. -
Ignored: noinline, always_inline, pure, const, nothrow, malloc, no_instrument_function, cdecl
- Unsupported: used, section, alias, + Unsupported: section, alias, visibility, regparm, stdcall, fastcall, all other target specific attributes @@ -354,7 +475,7 @@ work: Specifying attributes of variables.
Supported: cleanup, common, nocommon, deprecated, transparent_union, - unused, weak
+ unused, used, weak
Unsupported: aligned, mode, packed, section, shared, tls_model, @@ -375,7 +496,9 @@ work: __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). + point comparison macros (e.g., __builtin_islessequal), + __builtin_prefetch, __builtin_popcount[ll], + __builtin_clz[ll], and __builtin_ctz[ll].
The following extensions are known to be supported:
@@ -445,12 +568,6 @@ itself.-
-
- The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This -parser is significantly more standards compliant (and picky) than prior GCC -versions. For more information, see the C++ section of the GCC 3.4 release notes. -
- Destructors for local objects are not always run when a longjmp is performed. In particular, destructors for objects in the longjmping function and in the setjmp receiver function may not be run. @@ -492,27 +604,42 @@ href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes.
- none yet + +
- The C back-end produces code that violates the ANSI C Type-Based Alias +Analysis rules. As such, special options may be necessary to compile the code +(for example, GCC requires the -fno-strict-aliasing option). This +problem probably cannot be fixed. + +
- Zero arg vararg functions are not +supported. This should not affect LLVM produced by the C or C++ +frontends. + +
- The C backend does not correctly implement the llvm.stacksave or +llvm.stackrestore +intrinsics. This means that some code compiled by it can run out of stack +space if they depend on these (e.g. C99 varargs). +
- The C back-end produces code that violates the ANSI C Type-Based Alias -Analysis rules. As such, special options may be necessary to compile the code -(for example, GCC requires the -fno-strict-aliasing option). This -problem probably cannot be fixed. +
- On 21164s, some rare FP arithmetic sequences which may trap do not have the +appropriate nops inserted to ensure restartability. -
- Zero arg vararg functions are not -supported. This should not affect LLVM produced by the C or C++ -frontends. +
- C++ programs are likely to fail on IA64, as calls to setjmp are +made where the argument is not 16-byte aligned, as required on IA64. (Strictly +speaking this is not a bug in the IA64 back-end; it will also be encountered +when building C++ programs using the C back-end.) + +
- The C++ front-end does not use IA64 +ABI compliant layout of v-tables. In particular, it just stores function +pointers instead of function descriptors in the vtable. This bug prevents +mixing C++ code compiled with LLVM with C++ objects compiled by other C++ +compilers. + +
- There are a few ABI violations which will lead to problems when mixing LLVM +output with code built with other compilers, particularly for floating-point +programs. + +
- Defining vararg functions is not supported (but calling them is ok). + +
- The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not + support the 64-bit SPARC ABI (-m64). +
- [sparcv9] SparcV9 backend miscompiles +several programs in the LLVM test suite +
- The SparcV9 backend is slated to be removed before the LLVM 1.8 + release.
-
-
-
-
-
+
+
-
+
-
+
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.
+A wide variety of additional information is available on the LLVM web page, including documentation 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 +us via the mailing lists.
+ The LLVM Compiler Infrastructure
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