From 49123fd58c52833dd40702c30dd05e2c40156f33 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 6 Apr 2011 06:29:50 +0000
Subject: [PATCH] Finish up the first draft of the release notes.

improvements are welcome, please commit any changes directly to SVN.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128992 91177308-0d34-0410-b5e6-96231b3b80d8
---
 docs/CodeGenerator.html |   2 +-
 docs/ReleaseNotes.html  | 207 +++++++++++++++++-----------------------
 2 files changed, 91 insertions(+), 118 deletions(-)

diff --git a/docs/CodeGenerator.html b/docs/CodeGenerator.html
index a84534644cf..02869f63a45 100644
--- a/docs/CodeGenerator.html
+++ b/docs/CodeGenerator.html
@@ -2532,7 +2532,7 @@ OperandTy: VirtReg, | VirtReg, UnsImm, VirtReg,   SignExtImm  PhysReg
 
 <div class="doc_text">
 
-<p>x86 has an experimental feature which provides
+<p>x86 has an feature which provides
    the ability to perform loads and stores to different address spaces
    via the x86 segment registers.  A segment override prefix byte on an
    instruction causes the instruction's memory access to go to the specified
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index 5d140258173..22f0db34723 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -28,11 +28,13 @@
   <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
 </div>
 
+<!--
 <h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.9
 release.<br>
 You may prefer the
 <a href="http://llvm.org/releases/2.8/docs/ReleaseNotes.html">LLVM 2.8
 Release Notes</a>.</h1>
+ -->
 
 <!-- *********************************************************************** -->
 <h1>
@@ -579,35 +581,34 @@ infrastructure, which allows us to implement more aggressive algorithms and make
 it run faster:</p>
 
 <ul>
-<!-- SplitKit -->
-  
 <li>The pre-register-allocation (preRA) instruction scheduler models register
   pressure much more accurately in some cases. This allows the adoption of more
-    aggressive scheduling heuristics.
+  aggressive scheduling heuristics without causing spills to be generated.
 </li>
   
-  LiveDebugVariables is a new pass that keeps track of debugging information for
-  user variables that are kept in registers in optimized builds.
-  
-
-Scheduler now models operand latency and pipeline forwarding.
-  
-Major regalloc rewrite, not on by default for 2.9 and not advised to use it.
- * New basic register allocator that can be used as a safe fallback when
-   debugging. Enable with -regalloc=basic.
- * New infrastructure for live range splitting. SplitKit can break a live
-   interval into smaller pieces while preserving SSA form, and SpillPlacement
-   can help find the best split points. This is a work in progress so the API
-   is changing quickly.
- * The inline spiller has learned to clean up after live range splitting. It
-   can hoist spills out of loops, and it can eliminate redundant spills.
-   Rematerialization works with live range splitting.
- * New greedy register allocator using live range splitting. This will be the
-   default register allocator in the next LLVM release, but it is not turned on
-   by default in 2.9.
-
-
-
+<li>LiveDebugVariables is a new pass that keeps track of debugging information
+  for user variables that are promoted to registers in optimized builds.</li>  
+
+<li>The scheduler now models operand latency and pipeline forwarding.</li>
+
+<li>A major register allocator infrastructure rewrite is underway.  It is not on
+    by default for 2.9 and you are not advised to use it, but it has made
+    substantial progress in the 2.9 timeframe:
+  <ul>
+  <li>A new -regalloc=basic "basic" register allocator can be used as a simple
+      fallback when debugging.  It uses the new infrastructure.</li>
+  <li>New infrastructure is in place for live range splitting.  "SplitKit" can
+      break a live interval into smaller pieces while preserving SSA form, and
+      SpillPlacement can help find the best split points. This is a work in
+      progress so the API is changing quickly.</li>
+   <li>The inline spiller has learned to clean up after live range splitting. It
+      can hoist spills out of loops, and it can eliminate redundant spills.</li>
+   <li>Rematerialization works with live range splitting.</li>
+   <li>The new "greedy" register allocator using live range splitting. This will
+     be the default register allocator in the next LLVM release, but it is not
+     turned on by default in 2.9.</li>
+   </ul>
+</li>
 </ul>
 </div>
 
@@ -621,31 +622,31 @@ Major regalloc rewrite, not on by default for 2.9 and not advised to use it.
 </p>
 
 <ul>
-<li>
-X86: Reimplemented all of MMX to introduce a new LLVM IR x86_mmx type.  Now
-  random types like &lt;2 x i32&gt; are not iseld to mmx without emms.  The
-  -disable-mmx flag is gone now.
+<li>LLVM 2.9 includes a complete reimplementation of the MMX instruction set.
+  The reimplementation uses a new LLVM IR <a 
+  href="LangRef.html#t_x86mmx">x86_mmx</a> type to ensure that MMX operations
+  are <em>only</em> generated from source that uses MMX builtin operations. With
+  this, random types like &lt;2 x i32&gt; are not turned into to MMX operations
+  (which can be catastrophic without proper "emms" insertion).  Because the X86
+  code generator always generates reliable code, the -disable-mmx flag is now
+  removed.
 </li>
   
-  <li>
-X86 support for FS/GS relative loads and stores using address space 256/257 are
-  reliable now.
-  </li>
+<li>X86 support for FS/GS relative loads and stores using <a 
+    href="CodeGenerator.html#x86_memory">address space 256/257</a> work reliably
+    now.</li>
   
-    <li>
-X86: Much better codegen for several cases using adc/sbb instead of cmovs for
-  conditional increment and other idioms.
-    </li>
+<li>LLVM 2.9 generates much better code in several cases by using adc/sbb to
+   avoid generation of conditional move instructions for conditional increment
+   and other idioms.</li>
 
-  <li>
-  The X86 backend has adopted a new preRA scheduling
-  mode, "list-ilp", to shorten the height of instruction schedules
-  without inducing register spills.
-  </li>
+<li>The X86 backend has adopted a new preRA scheduling mode, "list-ilp", to
+  shorten the height of instruction schedules without inducing register spills.
+</li>
 
-  MC assembler support for 3dNow! and 3DNowA instructions.
+<li>The MC assembler support for 3dNow! and 3DNowA instructions.</li>
   
-  <li>Several bugs have been fixed for Windows x64 code generator.</li>
+<li>Several bugs have been fixed for Windows x64 code generator.</li>
 </ul>
 
 </div>
@@ -660,17 +661,17 @@ X86: Much better codegen for several cases using adc/sbb instead of cmovs for
 </p>
 
 <ul>
-<li>ARM Fast ISel</li>
-<li>ARM: New code placement pass.</li>
-<li>ARM: Improved code generation for Cortex-A8 and Cortex-A9 CPUs.</li>
-<li>ARM: __builtin_prefetch turns into prefetch instructions.</li>
-<li>Countless ARM microoptimizations.</li>
+<li>The ARM backend now has a fast instruction selector, which dramatically
+     improves -O0 compile times.</li>
+<li>The ARM backend has new tuning for Cortex-A8 and Cortex-A9 CPUs.</li>
+<li>The __builtin_prefetch builtin (and llvm.prefetch intrinsic) is compiled
+    into prefetch instructions instead of being discarded.</li>
 
 <li>  The ARM backend preRA scheduler now models machine resources at cycle
   granularity. This allows the scheduler to both accurately model
   instruction latency and avoid overcommitting functional units.</li>
 
-
+<li>Countless ARM microoptimizations have landed in LLVM 2.9.</li>
 </ul>
 </div>
   
@@ -681,15 +682,16 @@ X86: Much better codegen for several cases using adc/sbb instead of cmovs for
 
 <div class="doc_text">
 <ul>
-  PPC: Switched to MCInstPrinter, and MCCodeEmitter.  Ready to implement support
-  for directly writing out mach-o object files, but noone seems interested.
-  
-  MicroBlaze: major updates for aggressive delay slot filler, MC-based assembly
-  printing, assembly instruction parsing, ELF .o file emission, and MC
-  instruction disassembler.
-  
-  SPARC: Many improvements, including using the Y registers for multiplications
-  and addition of a simple delay slot filler.
+<li>MicroBlaze: major updates for aggressive delay slot filler, MC-based
+  assembly printing, assembly instruction parsing, ELF .o file emission, and MC
+  instruction disassembler have landed.</li>
+
+<li>SPARC: Many improvements, including using the Y registers for
+  multiplications and addition of a simple delay slot filler.</li>
+
+<li>PowerPC: The backend has been largely MC'ized and is ready to support
+  directly writing out mach-o object files.  Noone seems interested in finishing
+  this final step though.</li>
   
 </ul>
 </div>
@@ -706,48 +708,26 @@ on LLVM 2.8, this section lists some "gotchas" that you may run into upgrading
 from the previous release.</p>
 
 <ul>
-  last release for llvm-gcc
+<li><b>This is the last release to support the llvm-gcc frontend.</b></li>
 
-  <li>
-    New naming rules in coding standards: CodingStandards.html#ll_naming
-  </li>
+<li>LLVM has a new <a href="CodingStandards.html#ll_naming">naming
+  convention standard</a>, though the codebase hasn't fully adopted it yet.</li>
   
+<li>The new DIBuilder class provides a simpler interface for front ends to
+    encode debug info in LLVM IR, and has replaced DIFactory.</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;
-  Ty = DebugFactory.CreateDerivedType(DW_TAG_volatile_type,
-  findRegion(TYPE_CONTEXT(type)),
-  StringRef(),
-  getOrCreateFile(main_input_filename),
-  0 /*line no*/,
-  NodeSizeInBits(type),
-  NodeAlignInBits(type),
-  0 /*offset */,
-  0 /* flags */,
-  MainTy);
-  can be replaced by
-  DbgTy = DBuilder.createQualifiedType(DW_TAG_volatile_type, MainTy); 
-DIFactory is gone now.
-  
-    
-
-
-
-  
-  LoopIndexSplit pass was removed, unmaintained.
-  LiveValues, SimplifyHalfPowrLibCalls, and GEPSplitter were removed.
-  Removed the PartialSpecialization pass, it was unmaintained and buggy.
-  
-  DIFactory removed, use DIBuilder instead.
-  
-  Triple::normalize is new, llvm triples are always stored in normalized form internally.
-  
-  Triple x86_64--mingw64 is obsoleted. Use x86_64--mingw32 instead.
+<li>LLVM IR and other tools always work on normalized target triples (which have
+  been run through <tt>Triple::normalize</tt>).</li>
 
-  PointerTracking has been removed from mainline, moved to ClamAV.
+<li>The target triple x86_64--mingw64 is obsoleted. Use x86_64--mingw32 
+  instead.</li>
 
+<li>The PointerTracking pass has been removed from mainline, and moved to The
+  ClamAV project (its only client).</li>
+    
+<li>The LoopIndexSplit, LiveValues, SimplifyHalfPowrLibCalls, GEPSplitter, and
+  PartialSpecialization passes were removed.  They were unmaintained,
+  buggy, or decided to be a bad idea.</li>
 </ul>
 
 </div>
@@ -763,27 +743,18 @@ DIFactory is gone now.
   LLVM API changes are:</p>
 
 <ul>
-  
-  include/llvm/System merged into include/llvm/Support.
-  
-  
-  APInt API changes, see PR5207.
-  
-  MVT::Flag renamed to MVT::Glue
-  
-  
-  error_code + libsystem + PathV2 changes
-  The system_error header from C++0x was added.
-  * Use if (error_code ec = function()) to check for error conditions
-  from functions which return it.
-  * error_code::message returns a human readable description of the error.
-  
-  PathV1 has been deprecated in favor of PathV2 (sorry I didn't finish
-  this before the release).
-  * No Path class, use a r-value convertible to a twine instead.
-  * Assumes all paths are UTF-8.
-  
+<li>include/llvm/System merged into include/llvm/Support.</li>
+<li>The <a href="http://llvm.org/PR5207">llvm::APInt API</a> was significantly
+  cleaned up.</li>
+
+<li>In the code generator, MVT::Flag was renamed to MVT::Glue to more accurately
+  describe its behavior.</li>
 
+<li>The system_error header from C++0x was added, and is now pervasively used to
+  capture and handle i/o and other errors in LLVM.</li>
+  
+<li>The old sys::Path API has been deprecated in favor of the new PathV2 API,
+    which is more efficient and flexible.</li>
 </ul>
 </div>
 
@@ -820,7 +791,7 @@ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
 <li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ
     and XCore backends are experimental.</li>
 <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
-    other than darwin-i386 and darwin-x86_64. FIXME: Not true on ELF anymore?</li>
+    other than darwin and ELF X86 systems.</li>
     
 </ul>
 
@@ -962,6 +933,8 @@ Depending on it for anything serious is not advised.</p>
 
 <div class="doc_text">
 
+<p><b>LLVM 2.9 will be the last release of llvm-gcc.</b></p>
+
 <p>llvm-gcc is generally very stable for the C family of languages.  The only
    major language feature of GCC not supported by llvm-gcc is the
    <tt>__builtin_apply</tt> family of builtins.   However, some extensions
-- 
2.34.1