llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-01 00:33:09 +00:00

History

Hal Finkel c37f502d48 Phi speculation improvement for BasicAA This is a partial solution to PR14351. It removes some of the special significance of the first incoming phi value in the phi aliasing checking logic in BasicAA. In the context of a loop, the old logic assumes that the first incoming value is the interesting one (meaning that it is the one that comes from outside the loop), but this is often not the case. With this change, we now test first the incoming value that comes from a block other than the parent of the phi being tested. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168245 91177308-0d34-0410-b5e6-96231b3b80d8		2012-11-17 02:33:15 +00:00
..
IPA	Add doInitialization and doFinalization methods to ModulePass's, to allow them to be re-initialized and reused on multiple Module's.	2012-11-15 00:14:15 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp	Add a cost model analysis that allows us to estimate the cost of IR-level instructions.	2012-11-02 21:48:17 +00:00
BasicAliasAnalysis.cpp	Phi speculation improvement for BasicAA	2012-11-17 02:33:15 +00:00
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFGPrinter.cpp
CMakeLists.txt	Add a cost model analysis that allows us to estimate the cost of IR-level instructions.	2012-11-02 21:48:17 +00:00
CodeMetrics.cpp	Revert the majority of the next patch in the address space series:	2012-11-01 09:14:31 +00:00
ConstantFolding.cpp	llvm/ConstantFolding.cpp: Make ReadDataFromGlobal() and FoldReinterpretLoadFromConstPtr() Big-endian-aware.	2012-11-08 20:34:25 +00:00
CostModel.cpp	CostModel: add support for Vector Insert and Extract.	2012-11-02 22:31:56 +00:00
DbgInfoPrinter.cpp
DependenceAnalysis.cpp	DependenceAnalysis: Print all dependency pairs when dumping. Update all testcases.	2012-11-13 12:12:02 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
InlineCost.cpp	Revert the majority of the next patch in the address space series:	2012-11-01 09:14:31 +00:00
InstCount.cpp
InstructionSimplify.cpp	Make this easier to understand, as suggested by Chandler.	2012-11-16 20:53:08 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp	Hoist out some work done inside a loop doing a linear scan over all	2012-10-26 04:43:47 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp	Revert the series of commits starting with r166578 which introduced the	2012-11-01 08:07:29 +00:00
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp	Revert the series of commits starting with r166578 which introduced the	2012-11-01 08:07:29 +00:00
MemoryDependenceAnalysis.cpp	Ignore unreachable blocks when doing memory dependence analysis on non-local	2012-10-23 18:37:11 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PathNumbering.cpp
PathProfileInfo.cpp
PathProfileVerifier.cpp
PHITransAddr.cpp
PostDominators.cpp
ProfileDataLoader.cpp	Remove code to saturate profile counts.	2012-10-29 17:27:39 +00:00
ProfileDataLoaderPass.cpp
ProfileEstimatorPass.cpp
ProfileInfo.cpp
ProfileInfoLoader.cpp
ProfileInfoLoaderPass.cpp
ProfileVerifierPass.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Revert the series of commits starting with r166578 which introduced the	2012-11-01 08:07:29 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	Revert the series of commits starting with r166578 which introduced the	2012-11-01 08:07:29 +00:00
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	Revert the majority of the next patch in the address space series:	2012-11-01 09:14:31 +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))

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