llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-11-02 22:04:55 +00:00

History

Nick Lewycky 72dba254ae Fix an oversight in isPotentiallyReachable where we wouldn't do any CFG-walking to find loops if the From and To instructions were in the same block. Refactor the code a little now that we need to fill to start the CFG-walking algorithm with more than one starting basic block sometimes. Special thanks to Andrew Trick for catching an error in my understanding of natural loops in code review. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188236 91177308-0d34-0410-b5e6-96231b3b80d8		2013-08-13 00:03:47 +00:00
..
IPA	Disable inlining between sanitized and non-sanitized functions.	2013-08-08 08:22:39 +00:00
AliasAnalysis.cpp	Reimplement isPotentiallyReachable to make nocapture deduction much stronger.	2013-07-27 01:24:00 +00:00
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp	Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size.	2013-07-14 04:42:23 +00:00
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFG.cpp	Fix an oversight in isPotentiallyReachable where we wouldn't do any CFG-walking	2013-08-13 00:03:47 +00:00
CFGPrinter.cpp
CMakeLists.txt	Also update CMakeLists.txt for r187283.	2013-07-27 01:25:51 +00:00
CodeMetrics.cpp
ConstantFolding.cpp	Slightly simplify code with helper functions	2013-08-12 23:15:58 +00:00
CostModel.cpp	Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size.	2013-07-11 16:22:38 +00:00
DependenceAnalysis.cpp	Remove extraneous semicolon.	2013-08-06 16:40:40 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp	Add ISD::FROUND for libm round()	2013-08-07 22:49:12 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp	Add 'const' qualifiers to static const char* variables.	2013-07-16 01:17:10 +00:00
LoopPass.cpp	Comment: try to clarify loop iteration order.	2013-07-20 23:10:31 +00:00
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp	Treat nothrow forms of ::operator delete and ::operator delete[] as	2013-07-21 23:11:42 +00:00
MemoryDependenceAnalysis.cpp
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PathNumbering.cpp
PathProfileInfo.cpp
PathProfileVerifier.cpp
PHITransAddr.cpp
PostDominators.cpp
ProfileDataLoader.cpp	Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size.	2013-07-14 04:42:23 +00:00
ProfileDataLoaderPass.cpp
ProfileEstimatorPass.cpp
ProfileInfo.cpp
ProfileInfoLoader.cpp
ProfileInfoLoaderPass.cpp
ProfileVerifierPass.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Fix a severe compile time problem when forming large SCEV expressions.	2013-07-31 02:43:40 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	Remove a bunch of old SCEVExpander FIXME's for preserving NoWrap.	2013-07-14 03:10:08 +00:00
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
TargetTransformInfo.cpp	SimplifyCFG: Use parallel-and and parallel-or mode to consolidate branch conditions	2013-07-27 00:01:07 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	Teach ValueTracking about address spaces	2013-08-10 17:34:08 +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.

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

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))

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