llvm-6502/lib/Analysis
Andrew Trick 37aa33bc11 A new algorithm for computing LoopInfo. Temporarily disabled.
-stable-loops enables a new algorithm for generating the Loop
forest. It differs from the original algorithm in a few respects:

- Not determined by use-list order.
- Initially guarantees RPO order of block and subloops.
- Linear in the number of CFG edges.
- Nonrecursive.

I didn't want to change the LoopInfo API yet, so the block lists are
still inclusive. This seems strange to me, and it means that building
LoopInfo is not strictly linear, but it may not be a problem in
practice. At least the block lists start out in RPO order now. In the
future we may add an attribute or wrapper analysis that allows other
passes to assume RPO order.

The primary motivation of this work was not to optimize LoopInfo, but
to allow reproducing performance issues by decomposing the compilation
stages. I'm often unable to do this with the current LoopInfo, because
the loop tree order determines Loop pass order. Serializing the IR
tends to invert the order, which reverses the optimization order. This
makes it nearly impossible to debug interdependent loop optimizations
such as LSR.

I also believe this will provide more stable performance results across time.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158790 91177308-0d34-0410-b5e6-96231b3b80d8
2012-06-20 05:23:33 +00:00
..
IPA Handle intrinsics in GlobalsModRef. Fixes pr12351. 2012-03-28 21:31:24 +00:00
AliasAnalysis.cpp Move the capture analysis from MemoryDependencyAnalysis to a more general place 2012-05-14 20:35:04 +00:00
AliasAnalysisCounter.cpp Persuade GCC that there is nothing worth warning about here (there isn't). 2012-02-05 14:20:11 +00:00
AliasAnalysisEvaluator.cpp Remove unnecessary default cases in switches that cover all enum values. 2012-01-10 16:47:17 +00:00
AliasDebugger.cpp Extend the AliasAnalysis::pointsToConstantMemory interface to allow it 2010-11-08 16:45:26 +00:00
AliasSetTracker.cpp Have AliasSet::aliasesUnknownInst use pointer TBAA info when available 2012-02-10 15:52:39 +00:00
Analysis.cpp C API functions must be able to see their extern "C" definitions, or it will be impossible to call them from C. 2011-08-19 01:36:54 +00:00
BasicAliasAnalysis.cpp Duncan pointed out that if the alignment isn't explicitly specified, it defaults to the ABI alignment. Given that, make this code a bit more aggressive in such cases. 2012-02-27 23:16:46 +00:00
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 Fix intendation. 2012-05-10 23:38:07 +00:00
CFGPrinter.cpp Remove all remaining uses of Value::getNameStr(). 2011-11-15 16:27:03 +00:00
CMakeLists.txt Pull the implementation of the code metrics out of the inline cost 2012-03-16 05:51:52 +00:00
CodeMetrics.cpp A pile of long over-due refactorings here. There are some very, *very* 2012-05-04 00:58:03 +00:00
ConstantFolding.cpp Reapply r155682, making constant folding more consistent, with a fix to work 2012-04-27 17:50:22 +00:00
DbgInfoPrinter.cpp Fix for DbgInfoPrinter.cpp:174:12: warning: ‘LineNo’ may be used uninitialized in this function. 2011-09-21 23:34:23 +00:00
DebugInfo.cpp Actually support DW_TAG_rvalue_reference_type that we were trying 2012-05-19 01:36:37 +00:00
DIBuilder.cpp Add support for enum forward declarations. 2012-06-01 00:22:32 +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 remove the blank line from previous ci. 2012-02-04 03:18:47 +00:00
InlineCost.cpp Fix typos found by http://github.com/lyda/misspell-check 2012-06-02 10:20:22 +00:00
InstCount.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
InstructionSimplify.cpp Remove extraneous ';'. 2012-05-17 20:27:58 +00:00
Interval.cpp
IntervalPartition.cpp Now with fewer extraneous semicolons! 2010-10-07 22:25:06 +00:00
IVUsers.cpp Cleanup IVUsers::addUsersIfInteresting. 2012-03-22 17:47:33 +00:00
LazyValueInfo.cpp allow LazyValueInfo::getEdgeValue() to reason about multiple edges from the same switch instruction by doing union of ranges (which may still be conservative, but it's more aggressive than before) 2012-05-18 21:02:10 +00:00
LibCallAliasAnalysis.cpp Now with fewer extraneous semicolons! 2010-10-07 22:25:06 +00:00
LibCallSemantics.cpp Thread const correctness through a bunch of AliasAnalysis interfaces and 2010-08-03 21:48:53 +00:00
Lint.cpp Always compute all the bits in ComputeMaskedBits. 2012-04-04 12:51:34 +00:00
LLVMBuild.txt LLVMBuild: Introduce a common section which currently has a list of the 2011-12-12 22:45:54 +00:00
Loads.cpp enhance jump threading to preserve TBAA information when PRE'ing loads, 2012-03-13 18:07:41 +00:00
LoopDependenceAnalysis.cpp More dead code removal (using -Wunreachable-code) 2012-01-20 21:51:11 +00:00
LoopInfo.cpp A new algorithm for computing LoopInfo. Temporarily disabled. 2012-06-20 05:23:33 +00:00
LoopPass.cpp Take out the debug info probe stuff. It's making some changes to 2012-03-23 03:54:05 +00:00
Makefile
MemDepPrinter.cpp Mark some static arrays as const. 2012-05-24 06:35:32 +00:00
MemoryBuiltins.cpp remove calls to calloc if the allocated memory is not used (it was already being done for malloc) 2012-05-03 22:08:19 +00:00
MemoryDependenceAnalysis.cpp Fix typos found by http://github.com/lyda/misspell-check 2012-06-02 10:20:22 +00:00
ModuleDebugInfoPrinter.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
NoAliasAnalysis.cpp Use the new addEscapingValue callback to update GlobalsModRef when GVN adds PHIs of GEPs. For the moment, 2011-01-03 23:51:43 +00:00
PathNumbering.cpp [unwind removal] We no longer have 'unwind' instructions being generated, so 2012-02-06 21:16:41 +00:00
PathProfileInfo.cpp Implementation of path profiling. 2011-01-29 01:09:53 +00:00
PathProfileVerifier.cpp Remove all remaining uses of Value::getNameStr(). 2011-11-15 16:27:03 +00:00
PHITransAddr.cpp Uniformize the InstructionSimplify interface by ensuring that all routines 2012-03-13 11:42:19 +00:00
PostDominators.cpp remove postdom frontiers, because it is dead. Forward dom frontiers are 2011-04-05 21:57:17 +00:00
ProfileEstimatorPass.cpp Remove all remaining uses of Value::getNameStr(). 2011-11-15 16:27:03 +00:00
ProfileInfo.cpp Fix a ton of comment typos found by codespell. Patch by 2011-04-15 05:18:47 +00:00
ProfileInfoLoader.cpp Round 2 of dead private variable removal. 2012-06-06 19:47:08 +00:00
ProfileInfoLoaderPass.cpp Round 2 of dead private variable removal. 2012-06-06 19:47:08 +00:00
ProfileVerifierPass.cpp Move code into anonymous namespaces. 2011-11-26 23:01:57 +00:00
README.txt When checking whether the special handling for an addrec increment which 2010-04-26 21:46:36 +00:00
RegionInfo.cpp Rename the Region::block_iterator to Region::block_node_iterator, and 2012-05-04 20:55:23 +00:00
RegionPass.cpp Rename the Region::block_iterator to Region::block_node_iterator, and 2012-05-04 20:55:23 +00:00
RegionPrinter.cpp Rename the Region::block_iterator to Region::block_node_iterator, and 2012-05-04 20:55:23 +00:00
ScalarEvolution.cpp Fix typos found by http://github.com/lyda/misspell-check 2012-06-02 10:20:22 +00:00
ScalarEvolutionAliasAnalysis.cpp Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 2010-10-19 17:21:58 +00:00
ScalarEvolutionExpander.cpp LSR fix: add a missing phi check during IV hoisting. 2012-05-22 17:39:59 +00:00
ScalarEvolutionNormalization.cpp More dead code removal (using -Wunreachable-code) 2012-01-20 21:51:11 +00:00
SparsePropagation.cpp Taken into account Duncan's comments for r149481 dated by 2nd Feb 2012: 2012-03-08 07:06:20 +00:00
Trace.cpp Remove all remaining uses of Value::getNameStr(). 2011-11-15 16:27:03 +00:00
TypeBasedAliasAnalysis.cpp Fix a ton of comment typos found by codespell. Patch by 2011-04-15 05:18:47 +00:00
ValueTracking.cpp Teach DeadStoreElimination to eliminate exit-block stores with phi addresses. 2012-05-10 18:57:38 +00:00

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))

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