llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-04 21:30:49 +00:00

History

Hal Finkel e14fb07357 Consider (x == -1) unlikely in BranchProbabilityInfo This adds another heuristic to BPI, similar to the existing heuristic that considers (x == 0) unlikely to be true. As suggested in the PACT'98 paper by Deitrich, Cheng, and Hwu, -1 is often used to indicate an invalid index, and equality comparisons with -1 are also unlikely to succeed. Local experimentation supports this hypothesis: This yields a 1-2% speedup in the test-suite sqlite benchmark on the PPC A2 core, with no significant regressions. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193855 91177308-0d34-0410-b5e6-96231b3b80d8		2013-11-01 10:58:22 +00:00
..
IPA	Merge CallGraph and BasicCallGraph.	2013-10-31 03:03:55 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp	Revert r193251 : Use address-taken to disambiguate global variable and indirect memops.	2013-10-27 03:08:44 +00:00
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp	Consider (x == -1) unlikely in BranchProbabilityInfo	2013-11-01 10:58:22 +00:00
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp
CMakeLists.txt
CodeMetrics.cpp
ConstantFolding.cpp
CostModel.cpp
DependenceAnalysis.cpp
DominanceFrontier.cpp
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp	Quick look-up for block in loop.	2013-10-26 03:08:02 +00:00
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	SCEV: Make the final add of an inbounds GEP nuw if we know that the index is positive.	2013-10-28 07:30:06 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	Fix SCEVExpander: don't try to expand quadratic recurrences outside a loop.	2013-10-25 21:35:56 +00:00
ScalarEvolutionNormalization.cpp	Fix LSR: don't normalize quadratic recurrences.	2013-10-25 21:35:52 +00:00
SparsePropagation.cpp
TargetTransformInfo.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
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))

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