llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-11-06 05:06:45 +00:00

History

David Majnemer cb9d4667b7 isKnownToBeAPowerOfTwo: (X & Y) + Y is a power of 2 or zero if y is also. This is useful if something that looks like (x & (1 << y)) ? 64 : 32 is the divisor in a modulo operation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182200 91177308-0d34-0410-b5e6-96231b3b80d8		2013-05-18 19:30:37 +00:00
..
IPA	This patch breaks up Wrap.h so that it does not have to include all of	2013-05-01 20:59:00 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp	Support in AAEvaluator to print alias queries of loads/stores with TBAA tags.	2013-03-22 22:34:41 +00:00
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp	This patch breaks up Wrap.h so that it does not have to include all of	2013-05-01 20:59:00 +00:00
BasicAliasAnalysis.cpp	Revert r176408 and r176407 to address PR15540.	2013-04-09 18:16:05 +00:00
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp	Remove unneeded #includes. Use forward declarations instead.	2013-03-10 00:34:01 +00:00
CFGPrinter.cpp
CMakeLists.txt	Remove -print-dbginfo as it is unused & bitrotten.	2013-03-08 18:17:46 +00:00
CodeMetrics.cpp
ConstantFolding.cpp	ConstantFolding: ComputeMaskedBits wants the scalar size for vectors.	2013-04-19 16:56:24 +00:00
CostModel.cpp	CostModel: Add parameter to instruction cost to further classify operand values	2013-04-04 23:26:21 +00:00
DependenceAnalysis.cpp
DominanceFrontier.cpp
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp	InstructionSimplify.cpp: Fix a ligature, "fi", to get rid of utf8 in comment.	2013-04-08 23:05:21 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp	Metadata for annotating loops as parallel. The first consumer for this	2013-02-13 18:08:57 +00:00
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp	Respect the 'nobuiltin' attribute when determining if a call is to a memory builtin.	2013-05-16 04:12:04 +00:00
MemoryDependenceAnalysis.cpp	Use only explicit bool conversion operators	2013-05-15 07:36:59 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PathNumbering.cpp
PathProfileInfo.cpp
PathProfileVerifier.cpp	Build fixes for STLPort + GCC	2013-03-29 18:48:45 +00:00
PHITransAddr.cpp
PostDominators.cpp
ProfileDataLoader.cpp
ProfileDataLoaderPass.cpp	Revert "Add LLVMContext::emitWarning methods and use them. <rdar://problem/12867368>"	2013-02-08 21:48:29 +00:00
ProfileEstimatorPass.cpp
ProfileInfo.cpp	Build fixes for STLPort + GCC	2013-03-29 18:48:45 +00:00
ProfileInfoLoader.cpp
ProfileInfoLoaderPass.cpp	Revert "Add LLVMContext::emitWarning methods and use them. <rdar://problem/12867368>"	2013-02-08 21:48:29 +00:00
ProfileVerifierPass.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp	RegionInfo: Do not crash if unreachable block is found	2013-05-03 15:48:34 +00:00
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Fix SCEV forgetMemoizedResults should search and destroy backedge exprs.	2013-03-26 03:14:53 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
TargetTransformInfo.cpp	CostModel: Add parameter to instruction cost to further classify operand values	2013-04-04 23:26:21 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp	Struct-path aware TBAA: change the format of TBAAStructType node.	2013-04-27 00:26:11 +00:00
ValueTracking.cpp	isKnownToBeAPowerOfTwo: (X & Y) + Y is a power of 2 or zero if y is also.	2013-05-18 19:30:37 +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))

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