llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-10-01 10:57:21 +00:00

History

Chandler Carruth 36b699f2b1 [C++11] Add range based accessors for the Use-Def chain of a Value. This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a Use iterator rather than a User iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update all of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over Users rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of Ts, but that can be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203364 91177308-0d34-0410-b5e6-96231b3b80d8		2014-03-09 03:16:01 +00:00
..
IPA	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
CFG.cpp
CFGPrinter.cpp
CMakeLists.txt
CodeMetrics.cpp
ConstantFolding.cpp	Allow constant folding of round function whenever feasible	2014-03-07 04:36:21 +00:00
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp
DominanceFrontier.cpp
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
LazyCallGraph.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp	Teach lint about address spaces	2014-03-06 17:33:55 +00:00
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
MemoryDependenceAnalysis.cpp
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
PostDominators.cpp
PtrUseVisitor.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +00:00
TargetTransformInfo.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	[C++11] Add range based accessors for the Use-Def chain of a Value.	2014-03-09 03:16:01 +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))

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