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LLVM backend for 6502
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a04a0649e1
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Owen Anderson a04a0649e1 Completely rework the datastructure GVN uses to represent the value number to leader mapping. Previously, 
this was a tree of hashtables, and a query recursed into the table for the immediate dominator ad infinitum
if the initial lookup failed.  This led to really bad performance on tall, narrow CFGs.

We can instead replace it with what is conceptually a multimap of value numbers to leaders (actually
represented by a hashtable with a list of Value*'s as the value type), and then
determine which leader from that set to use very cheaply thanks to the DFS numberings maintained by
DominatorTree.  Because there are typically few duplicates of a given value, this scan tends to be
quite fast.  Additionally, we use a custom linked list and BumpPtr allocation to avoid any unnecessary
allocation in representing the value-side of the multimap.

This change brings with it a 15% (!) improvement in the total running time of GVN on 403.gcc, which I
think is pretty good considering that includes all the "real work" being done by MemDep as well.

The one downside to this approach is that we can no longer use GVN to perform simple conditional progation,
but that seems like an acceptable loss since we now have LVI and CorrelatedValuePropagation to pick up
the slack.  If you see conditional propagation that's not happening, please file bugs against LVI or CVP.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119714 91177308-0d34-0410-b5e6-96231b3b80d8
2010-11-18 18:32:40 +00:00
autoconf fix the autoconf script to detect "has asmprinter"ness of a target by 2010-11-14 19:10:47 +00:00
bindings Try to fix ocaml bindings. 2010-10-08 00:36:21 +00:00
cmake Updated library dependencies. 2010-11-18 00:12:27 +00:00
docs add some justification for "using namespace llvm;" 2010-11-17 19:47:20 +00:00
examples Fix missing includes of "llvm/Analysis/Passes.h" in the tutorials. Thanks 2010-11-16 17:28:22 +00:00
include Document the units for the Size field. 2010-11-18 17:39:01 +00:00
lib Completely rework the datastructure GVN uses to represent the value number to leader mapping. Previously, 2010-11-18 18:32:40 +00:00
projects projects: Don't try to build libcxx if one happens to have it checked out into 2010-09-09 15:49:32 +00:00
runtime Rename 'libprofile/exported_symbols.lst' to 'libprofile/libprofile.exports'. 2010-09-03 15:42:45 +00:00
test Completely rework the datastructure GVN uses to represent the value number to leader mapping. Previously, 2010-11-18 18:32:40 +00:00
tools Make MCJIT work with CMake. 2010-11-17 23:35:07 +00:00
unittests Revert 119600 to unbreak the build. Francois, please investigate. 2010-11-18 01:38:07 +00:00
utils Remove ARM isel hacks that fold large immediates into a pair of add, sub, and, 2010-11-17 20:13:28 +00:00
website
build-for-llvm-top.sh Patch to build llvm with srcdir != objdir from 2009-01-23 08:42:38 +00:00
CMakeLists.txt Make MCJIT work with CMake. 2010-11-17 23:35:07 +00:00
configure fix the autoconf script to detect "has asmprinter"ness of a target by 2010-11-14 19:10:47 +00:00
CREDITS.TXT Convert a bunch of uses of 'bytecode' into 'bitcode'. This 2010-09-29 20:09:55 +00:00
LICENSE.TXT 2010 is upon us. 2010-01-09 18:40:31 +00:00
llvm.spec.in * llvm.spec.in: update blurb 2007-07-13 09:48:29 +00:00
Makefile Add --enable-docs. Patch by NAKAMURA Takumi. 2010-11-12 19:24:06 +00:00
Makefile.common Removed trailing whitespace from Makefiles. 2009-01-09 16:44:42 +00:00
Makefile.config.in Add --enable-docs. Patch by NAKAMURA Takumi. 2010-11-12 19:24:06 +00:00
Makefile.rules remove JIT support from the Alpha backend. The JIT will be moving to MC, 2010-11-14 18:24:41 +00:00
ModuleInfo.txt Remove trailing space. This is just an excuse to poke the 2010-10-05 20:32:15 +00:00
README.txt Undoing test commit blank space. 2010-09-29 17:39:29 +00:00

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