llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-05 12:31:33 +00:00

History

David Majnemer 2014c91510 ScalarEvolution: Construct SCEVDivision's Derived type instead of itself SCEVDivision::divide constructed an object of SCEVDivision<Derived> instead of Derived. divide would call visit which would cast the SCEVDivision<Derived> to type Derived. As it happens, SCEVDivision<Derived> and Derived currently have the same layout but this is fragile and grounds for UB. Instead, just construct Derived. No functional change intended. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222126 91177308-0d34-0410-b5e6-96231b3b80d8		2014-11-17 11:27:45 +00:00
..
IPA	CGSCC should not treat intrinsic calls like function calls (PR21403)	2014-11-12 18:25:47 +00:00
AliasAnalysis.cpp	Reformat partially, where I touched for whitespace changes.	2014-10-28 11:54:52 +00:00
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp	Use AA in LoadCombine	2014-11-03 23:19:16 +00:00
Analysis.cpp	Revert "Don't make assumptions about the name of private global variables."	2014-11-15 02:03:53 +00:00
AssumptionTracker.cpp
BasicAliasAnalysis.cpp	Revert r219432 - "Revert "[BasicAA] Revert "Revert r218714 - Make better use of zext and sign information."""	2014-11-13 09:16:54 +00:00
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp
BranchProbabilityInfo.cpp	Revert "IR: MDNode => Value"	2014-11-11 21:30:22 +00:00
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp
CFLAliasAnalysis.cpp	Remove redundant virtual on overriden functions.	2014-11-14 19:06:36 +00:00
CGSCCPassManager.cpp
CMakeLists.txt
CodeMetrics.cpp
ConstantFolding.cpp
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp	[DependenceAnalysis] Allow subscripts of different types	2014-11-16 16:52:44 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
FunctionTargetTransformInfo.cpp
InstCount.cpp
InstructionSimplify.cpp	InstSimplify: Optimize ICmpInst xform that uses computeKnownBits	2014-11-16 02:20:08 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp	Add Forward Control-Flow Integrity.	2014-11-11 21:08:02 +00:00
LazyCallGraph.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp	Revert "IR: MDNode => Value"	2014-11-11 21:30:22 +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	ScalarEvolution: Construct SCEVDivision's Derived type instead of itself	2014-11-17 11:27:45 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
ScopedNoAliasAA.cpp	Revert "IR: MDNode => Value"	2014-11-11 21:30:22 +00:00
SparsePropagation.cpp
StratifiedSets.h
TargetTransformInfo.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp	Revert "IR: MDNode => Value"	2014-11-11 21:30:22 +00:00
ValueTracking.cpp	Revert "IR: MDNode => Value"	2014-11-11 21:30:22 +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))

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