[llvm-commits] [llvm] r128990 - /llvm/trunk/docs/ReleaseNotes.html
Chris Lattner
sabre at nondot.org
Tue Apr 5 22:50:04 PDT 2011
Author: lattner
Date: Wed Apr 6 00:50:04 2011
New Revision: 128990
URL: http://llvm.org/viewvc/llvm-project?rev=128990&view=rev
Log:
continue writing.
Modified:
llvm/trunk/docs/ReleaseNotes.html
Modified: llvm/trunk/docs/ReleaseNotes.html
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ReleaseNotes.html?rev=128990&r1=128989&r2=128990&view=diff
==============================================================================
--- llvm/trunk/docs/ReleaseNotes.html (original)
+++ llvm/trunk/docs/ReleaseNotes.html Wed Apr 6 00:50:04 2011
@@ -399,25 +399,21 @@
<ul>
-<li>
- TBAA: On by default in clang. Disable it with -fno-strict-aliasing.
- Could be more aggressive for structs.
-</li>
-
-<li>New Nvidia PTX backend, not generally useful in 2.9 though.</li>
-
-<li>
-Much better debug info generated, particularly in optimized code situations.
+<li>Type Based Alias Analysis (TBAA) is now implemented and turned on by default
+ in Clang. This allows substantially better load/store optimization in some
+ cases. TBAA can be disabled by passing -fno-strict-aliasing.
</li>
-<li>
-inline asm multiple alternative constraint support.
-</li>
+<li>This release has seen a continued focus on quality of debug information.
+ LLVM now generates much higher fidelity debug information, particularly when
+ debugging optimized code.</li>
+
+<li>Inline assembly now supports multiple alternative constraints.</li>
+
+<li>A new backend for the NVIDIA PTX virtual ISA (used to target its GPUs) is
+ under rapid development. It is not generally useful in 2.9, but is making
+ rapid progress.</li>
-<li>
- New naming rules in coding standards: CodingStandards.html#ll_naming
-</li>
-
</ul>
</div>
@@ -432,13 +428,19 @@
expose new optimization opportunities:</p>
<ul>
-<li>udiv, ashr, lshr, shl now have exact and nuw/nsw bits:
- PR8862 / LangRef.html</li>
+<li>The <a href="LangRef.html#bitwiseops">udiv, ashr, lshr, and shl</a>
+ instructions now have support exact and nuw/nsw bits to indicate that they
+ don't overflow or shift out bits. This is useful for optimization of <a
+ href="http://llvm.org/PR8862">pointer differences</a> and other cases.</li>
+
+<li>LLVM IR now supports the <a href="LangRef.html#globalvars">unnamed_addr</a>
+ attribute to indicate that constant global variables with identical
+ initializers can be merged. This fixed <a href="http://llvm.org/PR8927">an
+ issue</a> where LLVM would incorrectly merge two globals which were supposed
+ to have distinct addresses.</li>
- unnamed_addr + PR8927
-
- new 'hotpatch' attribute: LangRef.html#fnattrs
-
+<li>The new <a href="LangRef.html#fnattrs">hotpatch attribute</a> has been added
+ to allow runtime patching of functions.</li>
</ul>
</div>
@@ -454,53 +456,61 @@
release includes a few major enhancements and additions to the optimizers:</p>
<ul>
- <li>LTO has been improved to use MC for parsing inline asm and now
- can build large programs like Firefox 4 on both OS X and Linux.</li>
-
-
- LoopIdiom: memset/memcpy formation and memset_pattern on darwin. Build with
- -ffreestanding or -fno-builtin if your memcpy is being compiled into infinite
- recursion.
-
- TargetLibraryInfo
-
- EarlyCSE pass.
- LoopInstSimplify pass.
+<li>Link Time Optimization (LTO) has been improved to use MC for parsing inline
+ assembly and now can build large programs like Firefox 4 on both Mac OS X and
+ Linux.</li>
+
+<li>The new -loop-idiom pass recognizes memset/memcpy loops (and memset_pattern
+ on darwin), turning them into library calls, which are typically better
+ optimized than inline code. If you are building a libc and notice that your
+ memcpy and memset functions are compiled into infinite recursion, please build
+ with -ffreestanding or -fno-builtin to disable this pass.</li>
+
+<li>A new -early-cse pass does a fast pass over functions to fold constants,
+ simplify expressions, perform simple dead store elimination, and perform
+ common subexpression elimination. It does a good job at catching some of the
+ trivial redundancies that exist in unoptimized code, making later passes more
+ effective.<,/li>
+
+<li>A new -loop-instsimplify pass is used to clean up loop bodies in the loop
+ optimizer.</li>
+
+<li>The new TargetLibraryInfo interface allows mid-level optimizations to know
+ whether the current target's runtime library has certain functions. For
+ example, the optimizer can now transform integer-only printf calls to call
+ iprintf, allowing reduced code size for embedded C libraries (e.g. newlib).
+</li>
-New <a href="WritingAnLLVMPass.html#RegionPass">RegionPass</a> infrastructure
- for region-based optimizations.
-
- Can optimize printf to iprintf when no floating point is used, for embedded
- targets with smaller iprintf implementation.
+<li>LLVM has a new <a href="WritingAnLLVMPass.html#RegionPass">RegionPass</a>
+ infrastructure for region-based optimizations.</li>
-Speedups to various mid-level passes:
- GVN is much faster on functions with deep dominator trees / lots of BBs.
- DomTree and DominatorFrontier are much faster to compute, and preserved by
- more passes (so they are computed less often)
- SRoA is also much faster and doesn't use DominanceFrontier.
-
-DSE is more aggressive with stores of different types: e.g. a large store
- following a small one to the same address.
+<li>Several optimizer passes have been substantially sped up:
+ GVN is much faster on functions with deep dominator trees and lots of basic
+ blocks. The dominator tree and dominance frontier passes are much faster to
+ compute, and preserved by more passes (so they are computed less often). The
+ -scalar-repl pass is also much faster and doesn't use DominanceFrontier.
+</li>
+
+<li>The Dead Store Elimination pass is more aggressive optimizing stores of
+ different types: e.g. a large store following a small one to the same address.
+ The MemCpyOptimizer pass handles several new forms of memcpy elimination.</li>
+<li>LLVM now optimizes various idioms for overflow detection into check of the
+ flag register on various CPUs. For example, we now compile:
-We now optimize various idioms for overflow detection into check of the flag
- register on various CPUs, e.g.:
+ <pre>
unsigned long t = a+b;
if (t < a) ...
+ </pre>
into:
- addq %rdi, %rbx
- jno LBB0_2
-
+ <pre>
+ addq %rdi, %rbx
+ jno LBB0_2
+ </pre>
+</li>
</ul>
-<!--
-<p>In addition to these features that are done in 2.8, there is preliminary
- support in the release for Type Based Alias Analysis
- Preliminary work on TBAA but not usable in 2.8.
- New CorrelatedValuePropagation pass, not on by default in 2.8 yet.
--->
-
</div>
<!--=========================================================================-->
@@ -516,46 +526,37 @@
in.</p>
<ul>
- <li>MC is now used by default for ELF systems on x86 and
- x86-64.</li>
- <li>MC supports and CodeGen uses the <tt>.loc</tt> directives for
- producing line number debug info. This produces more compact line
- tables.</li>
- <li>MC supports the <tt>.cfi_*</tt> directives for producing DWARF
- frame information, but it is still not used by CodeGen by default.</li>
- <li>COFF support?</li>
+<li>ELF MC support has matured enough for the integrated assembler to be turned
+ on by default in Clang on X86-32 and X86-64 ELF systems.</li>
+<li>MC supports and CodeGen uses the <tt>.file</tt> and <tt>.loc</tt> directives
+ for producing line number debug info. This produces more compact line
+ tables and easier to read .s files.</li>
+
+<li>MC supports the <tt>.cfi_*</tt> directives for producing DWARF
+ frame information, but it is still not used by CodeGen by default.</li>
+
- MC Assembler: X86 now generates much better diagnostics for common errors,
+<li>The MC assembler now generates much better diagnostics for common errors,
is much faster at matching instructions, is much more bug-compatible with
the GAS assembler, and is now generally useful for a broad range of X86
- assembly.
-
-
- ELF MC support: on by default in clang. There are still known missing features
- for human written assembly.
-
-
- Some basic <a href="CodeGenerator.html#mc">internals documentation</a> for MC.
+ assembly.</li>
- MC Assembler support for .file and .loc.
+<li>We now have some basic <a href="CodeGenerator.html#mc">internals
+ documentation</a> for MC.</li>
- tblgen support for assembler aliases: <a
- href="CodeGenerator.html#na_instparsing">MnemonicAlias and InstAlias</a>
-
- Win32 PE-COFF support in the MC assembler has made a lot of progress in the 2.9
- timeframe, but is still not generally useful. Please see
- "http://llvm.org/bugs/showdependencytree.cgi?id=9100&hide_resolved=1" for open bugs?
-
-
- lib/Object and llvm-objdump
- Experimental format independent object file manipulation library.
- * Supports PE/COFF and ELF.
- * llvm-nm extended to work with object files. Exactly matches
- binutils-nm for the files I've tested.
- * llvm-objdump added with support for disassembly (no relocations displayed).
+<li>.td files can now specify assembler aliases directly with the <a
+ href="CodeGenerator.html#na_instparsing">MnemonicAlias and InstAlias</a>
+ tblgen classes.</li>
+
+<li>LLVM now has an experimental format-independent object file manipulation
+ library (lib/Object). It supports both PE/COFF and ELF. The llvm-nm tool has
+ been extended to work with native object files, and the new llvm-objdump tool
+ supports disassembly of object files (but no relocations are displayed yet).
+</li>
-
+<li>Win32 PE-COFF support in the MC assembler has made a lot of progress in the
+ 2.9 timeframe, but is still not generally useful.</li>
</ul>
@@ -707,6 +708,12 @@
<ul>
last release for llvm-gcc
+ <li>
+ New naming rules in coding standards: CodingStandards.html#ll_naming
+ </li>
+
+
+
- DIBuilder provides simpler interface for front ends like Clang to encode debug info in LLVM IR.
- This interface hides implementation details (e.g. DIDerivedType, existence of compile unit etc..) that any front end should not know about.
For example, DIFactory DebugFactory;
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