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Duncan Sands b2cbdc35ba Simplify binary operations where one operand is a select instruction. 
The simplifications performed here never create new instructions, they
only return existing instructions (or a constant), and so are always a
win.  In theory they should transform (for example)
  %z = and i32 %x, %y
  %s = select i1 %cond, i32 %y, i32 %z
  %r = and i32 %x, %s
into
  %r = and i32 %x, y
but in practice they get into a fight with instcombine, and lose.
Unfortunately instcombine does a poor job in this case.  Nonetheless
I'm committing this transform to make it easier to discuss what to
do to make peace with instcombine.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118679 91177308-0d34-0410-b5e6-96231b3b80d8
2010-11-10 13:00:08 +00:00
..
IPA Make ModRefBehavior a lattice. Use this to clean up AliasAnalysis 2010-11-10 01:02:18 +00:00
AliasAnalysis.cpp Make ModRefBehavior a lattice. Use this to clean up AliasAnalysis 2010-11-10 01:02:18 +00:00
AliasAnalysisCounter.cpp Extend the AliasAnalysis::pointsToConstantMemory interface to allow it 2010-11-08 16:45:26 +00:00
AliasAnalysisEvaluator.cpp Reapply r116831 and r116839, converting AliasAnalysis to use 2010-10-19 22:54:46 +00:00
AliasDebugger.cpp Extend the AliasAnalysis::pointsToConstantMemory interface to allow it 2010-11-08 16:45:26 +00:00
AliasSetTracker.cpp Teach LICM and AliasSetTracker about AccessesArgumentsReadonly. 2010-11-09 19:58:21 +00:00
Analysis.cpp
BasicAliasAnalysis.cpp Make ModRefBehavior a lattice. Use this to clean up AliasAnalysis 2010-11-10 01:02:18 +00:00
CaptureTracking.cpp VAArg doesn't capture its operand. 2010-11-09 20:09:35 +00:00
CFGPrinter.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
CMakeLists.txt Introduce DIBuilder. It is intended to be a front-end friendly interface to emit debuggging information entries in LLVM IR. 2010-11-04 15:01:38 +00:00
ConstantFolding.cpp add uadd_ov/usub_ov to apint, consolidate constant folding 2010-10-14 00:05:07 +00:00
DbgInfoPrinter.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
DebugInfo.cpp Fix DIType verifier. The element 3 is DIFile now. 2010-11-02 20:41:13 +00:00
DIBuilder.cpp Use arrays instead of constant-sized SmallVectors. 2010-11-04 18:45:27 +00:00
DomPrinter.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
InlineCost.cpp
InstCount.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
InstructionSimplify.cpp Simplify binary operations where one operand is a select instruction. 2010-11-10 13:00:08 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp Reapply r116831 and r116839, converting AliasAnalysis to use 2010-10-19 22:54:46 +00:00
LiveValues.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
Loads.cpp Reapply r116831 and r116839, converting AliasAnalysis to use 2010-10-19 22:54:46 +00:00
LoopDependenceAnalysis.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp Memdep says that an instruction clobbers itself 2010-10-20 22:37:41 +00:00
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp Teach memdep to use pointsToConstantMemory to determine that loads 2010-10-29 01:14:04 +00:00
ModuleDebugInfoPrinter.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
NoAliasAnalysis.cpp Extend the AliasAnalysis::pointsToConstantMemory interface to allow it 2010-11-08 16:45:26 +00:00
PHITransAddr.cpp
PostDominators.cpp
ProfileEstimatorPass.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
ProfileInfo.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
ProfileInfoLoader.cpp
ProfileInfoLoaderPass.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
ProfileVerifierPass.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
README.txt
RegionInfo.cpp Make some symbols static, move classes into anonymous namespaces. 2010-10-22 17:35:07 +00:00
RegionPass.cpp Add RegionPass support. 2010-10-20 01:54:44 +00:00
RegionPrinter.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
ScalarEvolution.cpp Make ScalarEvolution::forgetLoop forget all contained loops too, because 2010-10-29 20:16:10 +00:00
ScalarEvolutionAliasAnalysis.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp Make ModRefBehavior a lattice. Use this to clean up AliasAnalysis 2010-11-10 01:02:18 +00:00
ValueTracking.cpp

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.

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

In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,

ScalarEvolution is forming this expression:

((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))

This could be folded to

(-1 * (trunc i64 undef to i32))

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