llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-13 20:32:21 +00:00

History

Hal Finkel 11af4b49b2 Add a dereferenceable attribute This attribute indicates that the parameter or return pointer is dereferenceable. Practically speaking, loads from such a pointer within the associated byte range are safe to speculatively execute. Such pointer parameters are common in source languages (C++ references, for example). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213385 91177308-0d34-0410-b5e6-96231b3b80d8		2014-07-18 15:51:28 +00:00
..
IPA	Add new lines to debugging information.	2014-07-03 02:11:49 +00:00
AliasAnalysis.cpp	Improve BasicAA CS-CS queries (redux)	2014-07-17 01:28:25 +00:00
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp	Improve BasicAA CS-CS queries (redux)	2014-07-17 01:28:25 +00:00
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp	BFI: Add constructor for Weight	2014-07-12 00:26:00 +00:00
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp
CGSCCPassManager.cpp
CMakeLists.txt
CodeMetrics.cpp
ConstantFolding.cpp	Look through addrspacecast in IsConstantOffsetFromGlobal	2014-07-14 22:39:26 +00:00
CostModel.cpp	[CostModel][x86] Improved cost model for alternate shuffles.	2014-07-03 22:24:18 +00:00
Delinearization.cpp
DependenceAnalysis.cpp
DominanceFrontier.cpp	Templatify DominanceFrontier.	2014-07-12 21:59:52 +00:00
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp	Rectify r213231. Use proper version of 'ComputeNumSignBits'.	2014-07-17 19:07:00 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp	Improve BasicAA CS-CS queries (redux)	2014-07-17 01:28:25 +00:00
PHITransAddr.cpp
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
TargetTransformInfo.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	Add a dereferenceable attribute	2014-07-18 15:51:28 +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))

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