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Okay, here's how to reproduce the problem: 1) Build a Release (or Release+Asserts) version of clang in the normal way. 2) Using the clang & clang++ binaries from (1), build a Release (or Release+Asserts) version of the same sources, but this time enable LTO --- specify the `-flto' flag on the command line. 3) Run the ARC migrator tests: $ arcmt-test --args -triple x86_64-apple-darwin10 -fsyntax-only -x objective-c++ ./src/tools/clang/test/ARCMT/cxx-rewrite.mm You'll see that the output isn't correct (the whitespace is off). The mis-compile is in the function `RewriteBuffer::RemoveText' in the clang/lib/Rewrite/Core/Rewriter.cpp file. When that function and RewriteRope.cpp are compiled with LTO and the `arcmt-test' executable is regenerated, you'll see the error. When those files are not LTO'ed, then the output of the `arcmt-test' is fine. It is *really* hard to get a testcase out of this. I'll file a PR with what I have currently. --- Reverse-merging r172363 into '.': U include/llvm/Analysis/MemoryBuiltins.h U lib/Analysis/MemoryBuiltins.cpp --- Reverse-merging r171325 into '.': U test/Transforms/InstCombine/objsize.ll G include/llvm/Analysis/MemoryBuiltins.h G lib/Analysis/MemoryBuiltins.cpp git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172756 91177308-0d34-0410-b5e6-96231b3b80d8 |
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.. | ||
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 | ||
CostModel.cpp | ||
DbgInfoPrinter.cpp | ||
DependenceAnalysis.cpp | ||
DominanceFrontier.cpp | ||
DomPrinter.cpp | ||
InlineCost.cpp | ||
InstCount.cpp | ||
InstructionSimplify.cpp | ||
Interval.cpp | ||
IntervalPartition.cpp | ||
IVUsers.cpp | ||
LazyValueInfo.cpp | ||
LibCallAliasAnalysis.cpp | ||
LibCallSemantics.cpp | ||
Lint.cpp | ||
LLVMBuild.txt | ||
Loads.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 | ||
ProfileDataLoader.cpp | ||
ProfileDataLoaderPass.cpp | ||
ProfileEstimatorPass.cpp | ||
ProfileInfo.cpp | ||
ProfileInfoLoader.cpp | ||
ProfileInfoLoaderPass.cpp | ||
ProfileVerifierPass.cpp | ||
PtrUseVisitor.cpp | ||
README.txt | ||
RegionInfo.cpp | ||
RegionPass.cpp | ||
RegionPrinter.cpp | ||
ScalarEvolution.cpp | ||
ScalarEvolutionAliasAnalysis.cpp | ||
ScalarEvolutionExpander.cpp | ||
ScalarEvolutionNormalization.cpp | ||
SparsePropagation.cpp | ||
TargetTransformInfo.cpp | ||
Trace.cpp | ||
TypeBasedAliasAnalysis.cpp | ||
ValueTracking.cpp |
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)) //===---------------------------------------------------------------------===//