llvm-6502

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

History

Benjamin Kramer 009da05e75 ComputeMaskedBits: Make knownzero computation more aggressive for ctlz with undef zero. unsigned foo(unsigned x) { return 31 - __builtin_clz(x); } now compiles into a single "bsrl" instruction on x86. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147255 91177308-0d34-0410-b5e6-96231b3b80d8		2011-12-24 17:31:46 +00:00
..
IPA	LLVMBuild: Remove trailing newline, which irked me.	2011-12-12 19:48:00 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp
BlockFrequencyInfo.cpp	Add some constantness to BranchProbabilityInfo and BlockFrequnencyInfo.	2011-12-20 20:03:10 +00:00
BranchProbabilityInfo.cpp	Make the unreachable probability much much heavier. The previous	2011-12-22 09:26:37 +00:00
CaptureTracking.cpp
CFGPrinter.cpp
CMakeLists.txt
ConstantFolding.cpp	Switch llvm.cttz and llvm.ctlz to accept a second i1 parameter which	2011-12-12 04:26:04 +00:00
DbgInfoPrinter.cpp
DebugInfo.cpp	Unweaken vtables as per http://llvm.org/docs/CodingStandards.html#ll_virtual_anch	2011-12-20 02:50:00 +00:00
DIBuilder.cpp	In DICompositeType, referenced to derived type is either metadata or null.	2011-12-16 17:51:31 +00:00
DominanceFrontier.cpp	Unweaken vtables as per http://llvm.org/docs/CodingStandards.html#ll_virtual_anch	2011-12-20 02:50:00 +00:00
DomPrinter.cpp
InlineCost.cpp	Continue counting intrinsics as instructions (except when they aren't, such as	2011-12-21 20:26:03 +00:00
InstCount.cpp
InstructionSimplify.cpp	Add support for vectors of pointers.	2011-12-05 06:29:09 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp	Clear the new cache.	2011-12-03 15:19:55 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt	LLVMBuild: Introduce a common section which currently has a list of the	2011-12-12 22:45:54 +00:00
Loads.cpp
LoopDependenceAnalysis.cpp
LoopInfo.cpp	Move Instruction::isSafeToSpeculativelyExecute out of VMCore and	2011-12-14 23:49:11 +00:00
LoopPass.cpp
Makefile
MemDepPrinter.cpp	Fix a stupid typo in MemDepPrinter.	2011-12-14 02:54:39 +00:00
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PathNumbering.cpp
PathProfileInfo.cpp
PathProfileVerifier.cpp
PHITransAddr.cpp	Move Instruction::isSafeToSpeculativelyExecute out of VMCore and	2011-12-14 23:49:11 +00:00
PostDominators.cpp
ProfileEstimatorPass.cpp
ProfileInfo.cpp
ProfileInfoLoader.cpp
ProfileInfoLoaderPass.cpp
ProfileVerifierPass.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	LSR: Fix another corner case in expansion of postinc users.	2011-12-20 01:42:24 +00:00
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	ComputeMaskedBits: Make knownzero computation more aggressive for ctlz with undef zero.	2011-12-24 17:31:46 +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))

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