-
-
-
+
LLVM now includes support for auto-generating large portions of the
+instruction selectors from target descriptions. This allows us to
+write patterns in the target .td file, instead of writing lots of
+nasty C++ code. Most of the PowerPC instruction selector is now
+generated from the PowerPC target description files and other targets
+are adding support that will be live for LLVM 1.7.
+
+
For example, here are some patterns used by the PowerPC backend. A
+floating-point multiply then subtract instruction (FMSUBS):
+
+
+(set F4RC:$FRT, (fsub (fmul F4RC:$FRA, F4RC:$FRC), F4RC:$FRB))
+
+
+
Exclusive-or by 16-bit immediate (XORI):
+
+
+(set GPRC:$dst, (xor GPRC:$src1, immZExt16:$src2))
+
+
+
Exclusive-or by 16-bit immediate shifted right 16-bits (XORIS):
+
+
+(set GPRC:$dst, (xor GPRC:$src1, imm16Shifted:$src2))
+
+
+
With these definitions, we teach the code generator how to combine these two
+instructions to xor an abitrary 32-bit immediate with the following
+definition. The first line specifies what to match (a xor with an arbitrary
+immediate) the second line specifies what to produce:
+
+
+
def : Pat<(xor GPRC:$in, imm:$imm),
+ (XORIS (XORI GPRC:$in, (LO16 imm:$imm)), (HI16 imm:$imm))>;
+
+
-In this release, the following missing features were implemented:
+
+
+
Instruction selectors using the refined instruction selection framework can now
+use a simple pre-pass scheduler included with LLVM 1.6. This scheduler is
+currently simple (cannot be configured much by the targets), but will be
+extended in the future.
+
+
+
+
It is now straight-forward to parameterize a target implementation, and
+provide a mapping from CPU names to sets of target parameters. LLC now supports
+a -mcpu=cpu option that lets you choose a subtarget by CPU name: use
+"llvm-as < /dev/null | llc -march=XXX -mcpu=help" to get a list of
+supported CPUs for target "XXX". It also provides a
+-mattr=+attr1,-attr2 option that can be used to control individual
+features of a target (the previous command will list available features as
+well).
-
-
-
+
This functionality is nice when you want tell LLC something like "compile to
+code that is specialized for the PowerPC G5, but doesn't use altivec code. In
+this case, using "llc -march=ppc32 -mcpu=g5 -mattr=-altivec".
-
-
+
+
-
-
+ - The JIT now uses mutexes to protect its internal data structures. This
+ allows multi-threaded programs to be run from the JIT or interpreter without
+ corruption of the internal data structures. See
+ PR418 and
+ PR540 for the details.
+
+ - LLVM on Win32 no longer requires sed,
+ flex, or bison when compiling with Visual C++.
+ - The llvm-test suite can now use the NAG Fortran to C compiler to compile
+ SPEC FP programs if available (allowing us to test all of SPEC'95 &
+ 2000).
+ - When bugpoint is grinding away and the user hits ctrl-C, it now
+ gracefully stops and gives what it has reduced so far, instead of
+ giving up completely. In addition, the JIT
+ debugging mode of bugpoint is much faster.
+ - LLVM now includes Xcode project files in the llvm/Xcode directory.
+ - LLVM now supports Mac OS X on Intel.
+ - LLVM now builds cleanly with GCC 4.1.
-
-
This release includes the following Code Quality
-improvements:
+
-
+ - The -globalopt pass can now statically evaluate C++ static
+ constructors when they are simple enough. For example, it can
+ now statically initialize "struct X { int a; X() : a(4) {} } g;".
+
+ - The Loop Strength Reduction pass has been completely rewritten, is far
+ more aggressive, and is turned on by default in the RISC targets. On PPC,
+ we find that it often speeds up programs from 10-40% depending on the
+ program.
+ - The code produced when exception handling is enabled is far more
+ efficient in some cases, particularly on Mac OS X.
+
-
-
In this release, the following bugs in the previous release
-were fixed:
+
-
-
Bugs fixed in the LLVM Core:
-
-
+- The Alpha backend is substantially more stable and robust than in LLVM 1.5.
+ For example, it now fully supports varargs functions. The Alpha backend
+ also now features beta JIT support.
+- The code generator contains a new component, the DAG Combiner. This allows
+ us to optimize lowered code (e.g. after 64-bit operations have been lowered
+ to use 32-bit registers on 32-bit targets) and do fine-grained bit-twiddling
+ optimizations for the backend.
+- The SelectionDAG infrastructure is far more capable and mature, able to
+ handle many new target peculiarities in a target-independent way.
+- The default register allocator is now far
+ faster on some testcases,
+ particularly on targets with a large number of registers (e.g. IA64
+ and PPC).
+
-
Bugs in the C/C++ front-end:
+
+
+
-
+ - A vast number of bugs have been fixed in the PowerPC backend and in
+ llvm-gcc when configured for Mac OS X (particularly relating to ABI
+ issues). For example:
+ PR449,
+ PR594,
+ PR603,
+ PR609,
+ PR630,
+ PR643,
+ and several others without bugzilla bugs.
+ - Several bugs in tail call support have been fixed.
+ - configure does not correctly detect gcc
+ version on cygwin.
+ - Many many other random bugs have been fixed. Query our bugzilla with a target of 1.6 for more
+ information.
-
@@ -163,12 +258,14 @@ were fixed:
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
@@ -190,7 +287,7 @@ 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.
@@ -210,16 +307,28 @@ 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
+ releases: -cee, -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 IA64 code generators are experimental.
+- The Alpha JIT is experimental.
+
+
+
+
+
+
Known problems with the LLVM Core
@@ -228,16 +337,8 @@ components, please contact us on the llvmdev list.
- - 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.
@@ -261,7 +362,7 @@ components, please contact us on the llvmdev list.
Initialization of global union variables can only be done with the largest union member.
+href="http://llvm.org/PR162">with the largest union member.
@@ -361,7 +462,9 @@ 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:
@@ -431,12 +534,6 @@ itself.
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.
-
@@ -476,6 +573,28 @@ href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes.