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History

Dan Gohman 731afb3b6e Revert r83606 and add comments explaining why it isn't safe. llvm-svn: 83649		2009-10-09 16:35:06 +00:00
..
IPA	Extend the StartPassTimer and StopPassTimer functions so that the	2009-09-28 00:07:05 +00:00
AliasAnalysis.cpp	Global Aliases are not identifiable objects.	2009-08-27 17:52:56 +00:00
AliasAnalysisCounter.cpp	Do not try to override non-virtual methods, especially	2009-09-06 20:02:00 +00:00
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp	Enhance analysis passes so that they apply the same analysis to malloc calls as to MallocInst.	2009-09-18 21:34:51 +00:00
CaptureTracking.cpp
CFGPrinter.cpp	The flag "--dot-cfg-only" is at the moment equivalent to the flag "--dot-cfg".	2009-09-19 11:25:44 +00:00
CMakeLists.txt	Update CMake build yet again after a source file was removed	2009-10-08 21:24:34 +00:00
ConstantFolding.cpp	Extend ConstantFolding to understand signed overflow variants	2009-10-05 22:53:52 +00:00
DbgInfoPrinter.cpp	Remove std::string uses from DebugInfo interface.	2009-09-29 18:40:58 +00:00
DebugInfo.cpp	It's possible for a global variable to be optimized out of a metadata object. So	2009-10-08 20:52:51 +00:00
InstCount.cpp
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp	Instead of testing whether an instruction dominates the loop preheader,	2009-09-27 15:30:00 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
LiveValues.cpp
LoopDependenceAnalysis.cpp
LoopInfo.cpp	Move the dominator verification code out of special code embedded within	2009-09-28 00:27:48 +00:00
LoopPass.cpp	Fix this debug output to handle the case where the loop has been deleted.	2009-09-28 15:40:01 +00:00
Makefile
MallocHelper.cpp	Add PR to this FIXME, looks like I didn't commit this change after all.	2009-10-07 09:22:55 +00:00
MemoryDependenceAnalysis.cpp	Revert r82404, it is causing a bootstrap miscompile. This is very very	2009-09-20 22:44:26 +00:00
PointerTracking.cpp	Introduce and use convenience methods for getting pointer types	2009-10-06 15:40:36 +00:00
PostDominators.cpp
ProfileEstimatorPass.cpp	Make ProfileEstimator even more robust on general CFGs.	2009-09-11 08:39:33 +00:00
ProfileInfo.cpp	Add the first functions for updating ProfileInfo.	2009-09-09 17:52:57 +00:00
ProfileInfoLoader.cpp	Reapplied r81355 with the problems fixed.	2009-09-16 11:35:50 +00:00
ProfileInfoLoaderPass.cpp	Reapplied r81355 with the problems fixed.	2009-09-16 11:35:50 +00:00
ProfileVerifierPass.cpp	Bugfix. Sorry.	2009-09-11 08:43:15 +00:00
README.txt	Create a README.txt for lib/Analysis, and add an entry.	2009-09-28 18:38:53 +00:00
ScalarEvolution.cpp	Revert r83606 and add comments explaining why it isn't safe.	2009-10-09 16:35:06 +00:00
ScalarEvolutionAliasAnalysis.cpp	Add some comments.	2009-08-29 23:36:57 +00:00
ScalarEvolutionExpander.cpp	Introduce and use convenience methods for getting pointer types	2009-10-06 15:40:36 +00:00
SparsePropagation.cpp	Add a comment explaining why you would ever want to do this.	2009-09-19 19:00:06 +00:00
Trace.cpp
ValueTracking.cpp	Handle sqrt in CannotBeNegativeZero. absf and absl	2009-09-25 20:54:50 +00:00

README.txt

Analysis Opportunities:

//===---------------------------------------------------------------------===//

In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:

  {1,+,3,+,2}<loop>

Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as

  (-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))

In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.

//===---------------------------------------------------------------------===//