llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-11-05 13:09:10 +00:00

History

Benjamin Kramer b6fdd022b7 PR13095: Give an inline cost bonus to functions using byval arguments. We give a bonus for every argument because the argument setup is not needed anymore when the function is inlined. With this patch we interpret byval arguments as a compact representation of many arguments. The byval argument setup is implemented in the backend as an inline memcpy, so to model the cost as accurately as possible we take the number of pointer-sized elements in the byval argument and give a bonus of 2 instructions for every one of those. The bonus is capped at 8 elements, which is the number of stores at which the x86 backend switches from an expanded inline memcpy to a real memcpy. It would be better to use the real memcpy threshold from the backend, but it's not available via TargetData. This change brings the performance of c-ray in line with gcc 4.7. The included test case tries to reproduce the c-ray problem to catch regressions for this benchmark early, its performance is dominated by the inline decision of a specific call. This only has a small impact on most code, more on x86 and arm than on x86_64 due to the way the ABI works. When building LLVM for x86 it gives a small inline cost boost to virtually any function using StringRef or STL allocators, but only a 0.01% increase in overall binary size. The size of gcc compiled by clang actually shrunk by a couple bytes with this patch applied, but not significantly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161413 91177308-0d34-0410-b5e6-96231b3b80d8		2012-08-07 11:13:19 +00:00
..
IPA
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFGPrinter.cpp
CMakeLists.txt
CodeMetrics.cpp
ConstantFolding.cpp
DbgInfoPrinter.cpp
DominanceFrontier.cpp
DomPrinter.cpp
InlineCost.cpp	PR13095: Give an inline cost bonus to functions using byval arguments.	2012-08-07 11:13:19 +00:00
InstCount.cpp
InstructionSimplify.cpp
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopDependenceAnalysis.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp
ModuleDebugInfoPrinter.cpp
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
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp

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))

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