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llvm-svn: 76438
This commit is contained in:
Dan Gohman 2009-07-20 17:44:17 +00:00
parent 00b05492f1
commit 721e006395
1 changed files with 5 additions and 7 deletions
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12
lib/Analysis/ScalarEvolutionExpander.cpp
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@ -215,13 +215,11 @@ static bool FactorOutConstant(const SCEV *&S,
/// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
/// instead of using ptrtoint+arithmetic+inttoptr. This helps
/// BasicAliasAnalysis analyze the result. However, it suffers from the
/// underlying bug described in PR2831. Addition in LLVM currently always
/// has two's complement wrapping guaranteed. However, the semantics for
/// getelementptr overflow are ambiguous. In the common case though, this
/// expansion gets used when a GEP in the original code has been converted
/// into integer arithmetic, in which case the resulting code will be no
/// more undefined than it was originally.
/// BasicAliasAnalysis analyze the result.
///
/// Design note: This depends on ScalarEvolution not recognizing inttoptr
/// and ptrtoint operators, as they may introduce pointer arithmetic
/// which may not be safely converted into getelementptr.
///
/// Design note: It might seem desirable for this function to be more
/// loop-aware. If some of the indices are loop-invariant while others