llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-20 09:30:43 +00:00

History

Chandler Carruth 7362ac7f8c Fix a crash on valid (if UB) bitcode that is produced for some global constants in C++11 mode. I have no idea why it required such particular circumstances to get here, the code seems clearly to rely upon unchecked assumptions. Specifically, when we decide to form an index into a struct type, we may have gone through (at least one) zero-length array indexing round, which would have left the offset un-adjusted, and thus not necessarily valid for use when indexing the struct type. This is just an canonicalization step, so the correct thing is to refuse to canonicalize nonsensical GEPs of this form. Implemented, and test case added. Fixes PR12642. Pair debugged and coded with Richard Smith. =] I credit him with most of the debugging, and preventing me from writing the wrong code. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155466 91177308-0d34-0410-b5e6-96231b3b80d8		2012-04-24 18:42:47 +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	Fix a crash on valid (if UB) bitcode that is produced for some global	2012-04-24 18:42:47 +00:00
DbgInfoPrinter.cpp
DebugInfo.cpp	Add a line number for the scope of the function (starting at the first	2012-04-03 00:43:49 +00:00
DIBuilder.cpp	Allow forward declarations to take a context. This helps the debugger	2012-04-23 19:00:11 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
InlineCost.cpp	Add two statistics to help track how we are computing the inline cost.	2012-04-11 10:15:10 +00:00
InstCount.cpp
InstructionSimplify.cpp
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp	Always compute all the bits in ComputeMaskedBits.	2012-04-04 12:51:34 +00:00
LLVMBuild.txt
Loads.cpp
LoopDependenceAnalysis.cpp
LoopInfo.cpp	Fix 12513: Loop unrolling breaks with indirect branches.	2012-04-10 05:14:42 +00:00
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	Revert "SCEV: When expanding a GEP the final addition to the base pointer has NUW but not NSW."	2012-04-17 06:33:57 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp	Fix ValueTracking to conclude that debug intrinsics are safe to	2012-04-07 19:22:18 +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))

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