llvm-6502/lib/Analysis
Philip Reames 90f3f15da5 Introduce a 'nonnull' metadata on Load instructions.
The newly introduced 'nonnull' metadata is analogous to existing 'nonnull' attributes, but applies to load instructions rather than call arguments or returns.  Long term, it would be nice to combine these into a single construct.   The value of the load is allowed to vary between successive loads, but null is not a valid value to be loaded by any load marked nonnull.

Reviewed by: Hal Finkel
Differential Revision:  http://reviews.llvm.org/D5220




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220240 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-20 22:40:55 +00:00
..
IPA Add functions for finding ephemeral values 2014-09-07 13:49:57 +00:00
AliasAnalysis.cpp Make AAMDNodes ctor and operator bool (!!!) explicit, mop up bugs and weirdness exposed by it. 2014-10-04 22:44:29 +00:00
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 AssumptionTracker: Don't create temporary CallbackVHs. 2014-10-11 19:13:01 +00:00
BasicAliasAnalysis.cpp Revert "[BasicAA] Revert "Revert r218714 - Make better use of zext and sign information."" 2014-10-09 19:48:12 +00:00
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp [modules] Stop excluding Support/Debug.h from the Support module. This header 2014-10-13 00:41:03 +00:00
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 [CFL-AA] CFL-AA should not assert on an va_arg instruction 2014-10-14 20:51:26 +00:00
CGSCCPassManager.cpp
CMakeLists.txt Add file to CMake build as well. 2014-09-18 00:39:20 +00:00
CodeMetrics.cpp Treat the WorkSet used to find ephemeral values as double-ended 2014-10-15 17:34:48 +00:00
ConstantFolding.cpp Remove duplicate function names from comments. NFC. 2014-10-02 15:13:22 +00:00
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp Analysis: cleanup 2014-08-26 02:03:40 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
FunctionTargetTransformInfo.cpp Add a new pass FunctionTargetTransformInfo. This pass serves as a 2014-09-18 00:34:14 +00:00
InstCount.cpp
InstructionSimplify.cpp InstCombine, InstSimplify: (%X /s C1) /s C2 isn't always 0 when C1 * C2 overflow 2014-10-11 10:20:01 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp [LVI] Add some additional comments about caching and context instructions 2014-10-16 00:40:05 +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 Fix a miscompile introduced in r220178. 2014-10-20 10:03:01 +00:00
LoopInfo.cpp
LoopPass.cpp Fix assertion in LICM doFinalization() 2014-09-24 16:48:31 +00:00
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp PR21145: Teach LLVM about C++14 sized deallocation functions. 2014-10-03 20:17:06 +00:00
MemoryDependenceAnalysis.cpp Silence a -Wsign-compare warning. NFC. 2014-10-02 13:17:11 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp Simplify code. No functionality change. 2014-10-05 12:21:57 +00:00
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 Revert "r219834 - Teach ScalarEvolution to sharpen range information" 2014-10-15 23:46:04 +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 Ignore annotation function calls in cost computation 2014-09-26 17:48:40 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp Introduce a 'nonnull' metadata on Load instructions. 2014-10-20 22:40:55 +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))

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