llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-18 10:31:57 +00:00

History

Jiangning Liu de3646b278 Add two thresholds lvi-overdefined-BB-threshold and lvi-overdefined-threshold for LVI algorithm. For a specific value to be lowered, when the number of basic blocks being checked for overdefined lattice value is larger than lvi-overdefined-BB-threshold, or the times of encountering overdefined value for a single basic block is larger than lvi-overdefined-threshold, the LVI algorithm will stop further lowering the lattice value. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218231 91177308-0d34-0410-b5e6-96231b3b80d8		2014-09-22 02:23:05 +00:00
..
IPA
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
AssumptionTracker.cpp
BasicAliasAnalysis.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp
CFLAliasAnalysis.cpp
CGSCCPassManager.cpp
CMakeLists.txt	Add file to CMake build as well.	2014-09-18 00:39:20 +00:00
CodeMetrics.cpp
ConstantFolding.cpp
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp
DominanceFrontier.cpp
DomPrinter.cpp
FunctionTargetTransformInfo.cpp	Add a new pass FunctionTargetTransformInfo. This pass serves as a	2014-09-18 00:34:14 +00:00
InstCount.cpp
InstructionSimplify.cpp	InstSimplify: Don't allow (x srem y) urem y -> x srem y	2014-09-17 04:16:35 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp	Add two thresholds lvi-overdefined-BB-threshold and lvi-overdefined-threshold	2014-09-22 02:23:05 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Make use @llvm.assume for loop guards in ScalarEvolution	2014-09-07 21:37:59 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
ScalarEvolutionNormalization.cpp
ScopedNoAliasAA.cpp
SparsePropagation.cpp
StratifiedSets.h
TargetTransformInfo.cpp	Add a new pass FunctionTargetTransformInfo. This pass serves as a	2014-09-18 00:34:14 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	Fix an ODR violation consisting of two 'struct Query' in the global namespace.	2014-09-12 08:56:53 +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))

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