From: Chris Lattner <sabre@nondot.org>
Date: Sun, 8 Jun 2008 02:45:07 +0000 (+0000)
Subject: add some notes.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=0b83220aecf2873c31172c1b92e9cdbf06949f35;p=oota-llvm.git

add some notes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52087 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index 470f38da33f..9d66b6d1506 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -84,9 +84,22 @@ upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a previous
 LLVM release to do this.  One nice impact of this is that the LLVM regression
 test suite no longer depends on llvm-upgrade, which makes it run faster.</p>
 
-<p>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
-   IRBuilder.</p>
+<p>LLVM API Changes:</p>
 
+<ul>
+<li>Several core LLVM IR classes have migrated to use 'FOOCLASS::Create(...)'
+    instead of 'new FOOCLASS(...)' (e.g. where FOOCLASS=BasicBlock).  We hope to
+    standardize on FOOCLASS::Create for all IR classes in the future, but not
+    all of them have been moved over yet.</li>
+<li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
+   IRBuilder.</li>
+<li>MRegisterInfo was renamed to TargetRegisterInfo.</li>
+<li>The MappedFile class is gone, please use MemoryBuffer instead.</li>
+<li>The '-enable-eh' flag to LLC has been removed.  Now code should encode
+    whether it is safe to not generate unwind information for a function by
+    tagging the Function object with the 'nounwind' attribute.</li>
+
+</ul>
 </div>
 
 <!--=========================================================================-->
@@ -172,7 +185,8 @@ this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
 
 Common linkage?
 
-Atomic operation support, Alpha, X86, X86-64, PowerPC. "__sync_synchronize"
+Atomic operation support, Alpha, X86, X86-64, PowerPC. "__sync_synchronize", 
+"__sync_val_compare_and_swap", etc"
 
 <ul>
 <li>The C and Ocaml bindings have received additional improvements. The
@@ -182,31 +196,6 @@ over the LLVM IR, target data, and parameter attribute lists.</li>
   
 </div>
 
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="codegen">Code Generator Improvements</a>
-</div>
-
-<div class="doc_text">
-
-<p>We put a significant amount of work into the code generator infrastructure,
-which allows us to implement more aggressive algorithms and make it run
-faster:</p>
-
-<ul>
-<li>MemOperand in the code generator: describe me!.</li>
-<li>The target-independent code generator infrastructure now uses LLVM's APInt
-    class to handle integer values, which allows it to support integer types
-    larger than 64 bits. Note that support for such types is also dependent on
-    target-specific support. Use of APInt is also a step toward support for
-    non-power-of-2 integer sizes.</li>
-<li>Several compile time speedups for code with large basic blocks.</li>
-<li>Several improvements which make llc's <tt>--view-sunit-dags</tt>
-    visualization of scheduling dependency graphs easier to understand.</li>
-</ul>
-
-</div>
-
 <!--=========================================================================-->
 <div class="doc_subsection">
 <a name="optimizer">Optimizer Improvements</a>
@@ -234,17 +223,69 @@ for (i = LB; i < NUB; ++i)
   LOOP_BODY
 </pre>
 </li>
-<li>LLVM includes a new <tt>memcpy</tt> optimization pass which optimizes out dead
-<tt>memcpy</tt> calls, unneeded copies of aggregates, and handles the return slot
-optimization.  The LLVM optimizer now notices long sequences of consequtive
-stores and merges them into <tt>memcpy</tt>s where profitable.</li>
+
+<li>LLVM includes a new <tt>memcpy</tt> optimization pass which optimizes out
+dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and handles the
+return slot optimization.  The LLVM optimizer now notices long sequences of
+consequtive stores and merges them into <tt>memcpy</tt>s where profitable.</li>
+
 <li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
 <tt>memset</tt> is now more aggressive.</li> 
 
-<li>The aggressive dead code elimination (ADCE) optimization has been rewritten to make
-it both faster and safer in the presence of code containing infinite loops.  
-Some of its prior functionality has been factored out into the loop deletion
-pass, which <em>is</em> safe for infinite loops.</li>
+<li>The aggressive dead code elimination (ADCE) optimization has been rewritten
+to make it both faster and safer in the presence of code containing infinite
+loops.  Some of its prior functionality has been factored out into the loop
+deletion pass, which <em>is</em> safe for infinite loops.</li>
+
+<li>Several optimizations have been sped up, leading to faster code generation
+    with the same code quality.</li>
+    
+<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm
+    functions for C-based languages, has been rewritten to be a FunctionPass
+    instead a ModulePass.  This allows it to be run more often and to be
+    included at -O1 in llvm-gcc.  It was also extended to include more
+    optimizations and several corner case bugs are fixed.</li>
+
+<li>LLVM now includes a simple 'Jump Threading' pass, which attemps to simplify
+    the conditional branches with information about predecessor blocks.  This
+    simplifies the control flow graph.  This pass is pretty basic at this point,
+    but catches some important cases and provides a foundation to build off
+    of.</li>
+</ul>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="codegen">Code Generator Improvements</a>
+</div>
+
+<div class="doc_text">
+
+<p>We put a significant amount of work into the code generator infrastructure,
+which allows us to implement more aggressive algorithms and make it run
+faster:</p>
+
+<ul>
+<li>MemOperand in the code generator: describe me!.</li>
+
+<li>The target-independent code generator infrastructure now uses LLVM's APInt
+    class to handle integer values, which allows it to support integer types
+    larger than 64 bits. Note that support for such types is also dependent on
+    target-specific support. Use of APInt is also a step toward support for
+    non-power-of-2 integer sizes.</li>
+    
+<li>Several compile time speedups for code with large basic blocks.</li>
+
+<li>Several improvements which make llc's <tt>--view-sunit-dags</tt>
+    visualization of scheduling dependency graphs easier to understand.</li>
+    
+<li>The code generator allows targets to write patterns that generate subreg
+    references directly in .td files now.</li>
+    
+<li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for
+    <tt>memcpy</tt> calls introduced by the code generator when handling
+    pass-by-value structure argument copies.</li>
 </ul>
 
 </div>
@@ -265,7 +306,11 @@ pass, which <em>is</em> safe for infinite loops.</li>
     now interoperates very well on X86-64 systems with other compilers.</li>
 
 <li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
-    the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins.</li>
+    the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins.  Various
+    generic vector operations (insert/extract/shuffle) are much more efficient
+    when SSE 4.1 is enabled.  The JIT automatically takes advantage of these
+    instructions, but llvm-gcc must be explicitly told to use them, e.g. with
+    <tt>-march=penryn</tt>.</li>
        
 <li>The X86 backend now does a number of optimizations that aim to avoid
     converting numbers back and forth from SSE registers to the X87 floating
@@ -286,6 +331,8 @@ pass, which <em>is</em> safe for infinite loops.</li>
 
 <li>128-bit integers are now supported on x86-64 targets.</li>
 
+<li>The register allocator can now rematerialize PIC-base computations.</li>
+
 </ul>
   
 </div>
@@ -320,7 +367,8 @@ pass, which <em>is</em> safe for infinite loops.</li>
 
 <ul>
 <li>LLVM now builds with GCC 4.3.</li>
-<li>llvm2cpp tool has been folded into llc, use <tt>llc -march=cpp</tt></li>
+<li><tt>llvm2cpp</tt> tool has been folded into llc, use
+    <tt>llc -march=cpp</tt></li>
 </ul>
   
 </div>