llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-28 19:31:58 +00:00

History

Arnold Schwaighofer 3036182e99 BasicAA: Use reachabilty instead of dominance for checking value equality in phi cycles This allows the value equality check to work even if we don't have a dominator tree. Also add some more comments. I was worried about compile time impacts and did not implement reachability but used the dominance check in the initial patch. The trade-off was that the dominator tree was required. The llvm utility function isPotentiallyReachable cuts off the recursive search after 32 visits. Testing did not show any compile time regressions showing my worries unjustfied. No compile time or performance regressions at O3 -flto -mavx on test-suite + externals. Addresses review comments from r198290. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198400 91177308-0d34-0410-b5e6-96231b3b80d8		2014-01-03 05:47:03 +00:00
..
IPA	[inliner] Fix PR18206 by preventing inlining functions that call setjmp	2013-12-13 08:00:01 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp	In AliasSetTracker, do not change the alias set to "mod/ref" when adding	2013-09-12 20:15:50 +00:00
Analysis.cpp	delinearization of arrays	2013-11-12 22:47:20 +00:00
BasicAliasAnalysis.cpp	BasicAA: Use reachabilty instead of dominance for checking value equality in phi	2014-01-03 05:47:03 +00:00
BlockFrequencyInfo.cpp	BlockFrequencyInfo: Readded getEntryFreq.	2013-12-20 22:11:11 +00:00
BranchProbabilityInfo.cpp	[block-freq] Teach branch probability how to return the edge weight in between a BasicBlock and one of its successors.	2013-12-14 02:24:25 +00:00
CaptureTracking.cpp	CaptureTracking: Plug a loophole in the "too many uses" heuristic.	2013-10-03 13:24:02 +00:00
CFG.cpp
CFGPrinter.cpp
CMakeLists.txt	delinearization of arrays	2013-11-12 22:47:20 +00:00
CodeMetrics.cpp
ConstantFolding.cpp	Add addrspacecast instruction.	2013-11-15 01:34:59 +00:00
CostModel.cpp	Move variable into assert to avoid unused variable warning.	2013-09-17 21:13:57 +00:00
Delinearization.cpp	add more comments around the delinearization of arrays	2013-11-13 22:37:58 +00:00
DependenceAnalysis.cpp	add more comments around the delinearization of arrays	2013-11-13 22:37:58 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp	Teach MemoryBuiltins and InstructionSimplify that operator new never returns NULL.	2013-09-24 16:37:51 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp	Use size function instead of manually calculating it.	2013-11-10 03:18:50 +00:00
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp	Simplify code. No functionality change.	2013-11-13 20:18:38 +00:00
LoopPass.cpp
Makefile
MemDepPrinter.cpp	Fix typo.	2013-12-04 23:55:09 +00:00
MemoryBuiltins.cpp	Teach MemoryBuiltins about address spaces	2013-12-14 00:27:48 +00:00
MemoryDependenceAnalysis.cpp	Fixing a heisenbug where the memory dependence analysis behaves differently	2013-11-14 01:10:52 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp	Correct word hyphenations	2013-12-05 05:44:44 +00:00
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Annotate APInt methods where it's not clear whether they are in place with warn_unused_result.	2013-11-16 16:25:41 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	Don't #include heavy Dominators.h file in LoopInfo.h. This change reduces	2013-12-07 21:20:17 +00:00
ScalarEvolutionNormalization.cpp	Fix LSR: don't normalize quadratic recurrences.	2013-10-25 21:35:52 +00:00
SparsePropagation.cpp
TargetTransformInfo.cpp	Costmodel: Add support for horizontal vector reductions	2013-09-17 18:06:50 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp	TBAA: fix PR17620.	2013-10-22 01:40:25 +00:00
ValueTracking.cpp	Don't speculate loads under ThreadSanitizer	2013-11-21 07:29:28 +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))

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