llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-13 04:30:23 +00:00

History

Sanjoy Das de87c9165a Teach ScalarEvolution to sharpen range information. If x is known to have the range [a, b), in a loop predicated by (icmp ne x, a) its range can be sharpened to [a + 1, b). Get ScalarEvolution and hence IndVars to exploit this fact. This change triggers an optimization to widen-loop-comp.ll, so it had to be edited to get it to pass. This change was originally landed in r219834 but had a bug and broke ASan. It was reverted in r219878, and is now being re-landed after fixing the original bug. phabricator: http://reviews.llvm.org/D5639 reviewed by: atrick git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221839 91177308-0d34-0410-b5e6-96231b3b80d8		2014-11-13 00:00:58 +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
AssumptionTracker.cpp	Clean up assume intrinsic pattern matching, no need to check that the argument is a value.	2014-10-25 18:09:01 +00:00
BasicAliasAnalysis.cpp
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
CGSCCPassManager.cpp
CMakeLists.txt
CodeMetrics.cpp
ConstantFolding.cpp	[InstSimplify] Support constant folding to vector of pointers	2014-10-22 12:18:48 +00:00
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp	Reformat partially, where I touched for whitespace changes.	2014-10-28 11:54:52 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
FunctionTargetTransformInfo.cpp
InstCount.cpp
InstructionSimplify.cpp	InstSimplify: Exact shifts of X by Y are X if X has the lsb set	2014-11-05 00:59:59 +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	Revert "Teach the load analysis to allow finding available values which require" (r220277)	2014-10-21 23:49:52 +00:00
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	Teach ScalarEvolution to sharpen range information.	2014-11-13 00:00:58 +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	Add minnum / maxnum intrinsics	2014-10-21 23:00:20 +00:00
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))

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