llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-09 10:31:14 +00:00

History

Andrew Trick e08c32249f LSR Fix: check SCEV expression safety before expansion. All SCEV expressions used by LSR formulae must be safe to expand. i.e. they may not contain UDiv unless we can prove nonzero denominator. Fixes PR11356: LSR hoists UDiv. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160205 91177308-0d34-0410-b5e6-96231b3b80d8		2012-07-13 23:33:10 +00:00
..
IPA	RefreshCallGraph: ignore 'invoke intrinsic'. IntrinsicInst doesnt not recognize invoke, and shouldnt at this point, since the rest of LLVM codebase doesnt expect invoke of intrinsics	2012-06-29 17:49:32 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp	Reduce use list thrashing by using DenseMap's find_as for maps with ValueHandle keys.	2012-06-30 22:37:15 +00:00
Analysis.cpp
BasicAliasAnalysis.cpp	refactor the MemoryBuiltin analysis:	2012-06-21 15:45:28 +00:00
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFGPrinter.cpp
CMakeLists.txt	Update the CMake files.	2012-06-29 09:01:47 +00:00
CodeMetrics.cpp
ConstantFolding.cpp
DbgInfoPrinter.cpp	Move lib/Analysis/DebugInfo.cpp to lib/VMCore/DebugInfo.cpp and	2012-06-28 00:05:13 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
InlineCost.cpp
InstCount.cpp
InstructionSimplify.cpp
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp	IVUsers should only generate SCEV's for values that are safe to speculate.	2012-07-13 23:33:05 +00:00
LazyValueInfo.cpp	make LazyValueInfo analyze the default case of switch statements (we know that in the default branch the value cannot be any of the switch cases)	2012-06-28 16:13:37 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopDependenceAnalysis.cpp
LoopInfo.cpp	Enable the new LoopInfo algorithm by default.	2012-06-26 04:11:38 +00:00
LoopPass.cpp	Enable the new LoopInfo algorithm by default.	2012-06-26 04:11:38 +00:00
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp	fold PHI nodes in SizeOffsetEvaluator whenever possible.	2012-07-03 17:13:25 +00:00
MemoryDependenceAnalysis.cpp	refactor the MemoryBuiltin analysis:	2012-06-21 15:45:28 +00:00
ModuleDebugInfoPrinter.cpp	Move lib/Analysis/DebugInfo.cpp to lib/VMCore/DebugInfo.cpp and	2012-06-28 00:05:13 +00:00
NoAliasAnalysis.cpp
PathNumbering.cpp
PathProfileInfo.cpp
PathProfileVerifier.cpp
PHITransAddr.cpp
PostDominators.cpp
ProfileEstimatorPass.cpp
ProfileInfo.cpp
ProfileInfoLoader.cpp
ProfileInfoLoaderPass.cpp
ProfileVerifierPass.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Factor SCEV traversal code so I can use it elsewhere. No functionality.	2012-07-13 23:33:03 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	LSR Fix: check SCEV expression safety before expansion.	2012-07-13 23:33:10 +00:00
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	PHINode::hasConstantValue(): return undef if the PHI is fully recursive.	2012-07-03 21:15:40 +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))

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