llvm-6502

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

History

David Majnemer d5f73530de InstSimplify: Don't allow (x srem y) urem y -> x srem y Let's consider the case where: %x i16 = 32768 %y i16 = 384 %x srem %y = 65408 (%x srem %y) urem %y = 128 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217939 91177308-0d34-0410-b5e6-96231b3b80d8		2014-09-17 04:16:35 +00:00
..
IPA	Add functions for finding ephemeral values	2014-09-07 13:49:57 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp	Add a CFL Alias Analysis implementation	2014-09-02 21:43:13 +00:00
AssumptionTracker.cpp	Add an Assumption-Tracking Pass	2014-09-07 12:44:26 +00:00
BasicAliasAnalysis.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp	Modernize raw_fd_ostream's constructor a bit.	2014-08-25 18:16:47 +00:00
CFLAliasAnalysis.cpp	[CFLAA] Remove one final initializer list	2014-09-03 00:06:47 +00:00
CGSCCPassManager.cpp
CMakeLists.txt	Add an Assumption-Tracking Pass	2014-09-07 12:44:26 +00:00
CodeMetrics.cpp	Add functions for finding ephemeral values	2014-09-07 13:49:57 +00:00
ConstantFolding.cpp
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp	Analysis: cleanup	2014-08-26 02:03:40 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp	InstSimplify: Don't allow (x srem y) urem y -> x srem y	2014-09-17 04:16:35 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp	Make use of @llvm.assume from LazyValueInfo	2014-09-07 20:29:59 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Make use @llvm.assume for loop guards in ScalarEvolution	2014-09-07 21:37:59 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)	2014-09-07 18:57:58 +00:00
ScalarEvolutionNormalization.cpp	Fix typos in comments, NFC	2014-08-29 21:53:01 +00:00
ScopedNoAliasAA.cpp	Add override to overriden virtual methods, remove virtual keywords.	2014-09-03 11:41:21 +00:00
SparsePropagation.cpp
StratifiedSets.h	[CFLAA] And even more MSVC fixes	2014-09-02 23:50:01 +00:00
TargetTransformInfo.cpp	Rename getMaximumUnrollFactor -> getMaxInterleaveFactor; also rename option names controlling this variable.	2014-09-10 17:58:16 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	Fix an ODR violation consisting of two 'struct Query' in the global namespace.	2014-09-12 08:56:53 +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))

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