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Let's try this again... This reverts r219432, plus a bug fix. Description of the bug in r219432 (by Nick): The bug was using AllPositive to break out of the loop; if the loop break condition i != e is changed to i != e && AllPositive then the test_modulo_analysis_with_global test I've added will fail as the Modulo will be calculated incorrectly (as the last loop iteration is skipped, so Modulo isn't updated with its Scale). Nick also adds this comment: ComputeSignBit is safe to use in loops as it takes into account phi nodes, and the == EK_ZeroEx check is safe in loops as, no matter how the variable changes between iterations, zero-extensions will always guarantee a zero sign bit. The isValueEqualInPotentialCycles check is therefore definitely not needed as all the variable analysis holds no matter how the variables change between loop iterations. And this patch also adds another enhancement to GetLinearExpression - basically to convert ConstantInts to Offsets (see test_const_eval and test_const_eval_scaled for the situations this improves). Original commit message: This reverts r218944, which reverted r218714, plus a bug fix. Description of the bug in r218714 (by Nick): The original patch forgot to check if the Scale in VariableGEPIndex flipped the sign of the variable. The BasicAA pass iterates over the instructions in the order they appear in the function, and so BasicAliasAnalysis::aliasGEP is called with the variable it first comes across as parameter GEP1. Adding a %reorder label puts the definition of %a after %b so aliasGEP is called with %b as the first parameter and %a as the second. aliasGEP later calculates that %a == %b + 1 - %idxprom where %idxprom >= 0 (if %a was passed as the first parameter it would calculate %b == %a - 1 + %idxprom where %idxprom >= 0) - ignoring that %idxprom is scaled by -1 here lead the patch to incorrectly conclude that %a > %b. Revised patch by Nick White, thanks! Thanks to Lang to isolating the bug. Slightly modified by me to add an early exit from the loop and avoid unnecessary, but expensive, function calls. Original commit message: Two related things: 1. Fixes a bug when calculating the offset in GetLinearExpression. The code previously used zext to extend the offset, so negative offsets were converted to large positive ones. 2. Enhance aliasGEP to deduce that, if the difference between two GEP allocations is positive and all the variables that govern the offset are also positive (i.e. the offset is strictly after the higher base pointer), then locations that fit in the gap between the two base pointers are NoAlias. Patch by Nick White! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221876 91177308-0d34-0410-b5e6-96231b3b80d8 |
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.. | ||
2003-02-26-AccessSizeTest.ll | ||
2003-03-04-GEPCrash.ll | ||
2003-04-22-GEPProblem.ll | ||
2003-04-25-GEPCrash.ll | ||
2003-05-21-GEP-Problem.ll | ||
2003-06-01-AliasCrash.ll | ||
2003-07-03-BasicAACrash.ll | ||
2003-09-19-LocalArgument.ll | ||
2003-11-04-SimpleCases.ll | ||
2003-12-11-ConstExprGEP.ll | ||
2004-07-28-MustAliasbug.ll | ||
2006-03-03-BadArraySubscript.ll | ||
2006-11-03-BasicAAVectorCrash.ll | ||
2007-01-13-BasePointerBadNoAlias.ll | ||
2007-08-01-NoAliasAndCalls.ll | ||
2007-08-01-NoAliasAndGEP.ll | ||
2007-08-05-GetOverloadedModRef.ll | ||
2007-10-24-ArgumentsGlobals.ll | ||
2007-11-05-SizeCrash.ll | ||
2007-12-08-OutOfBoundsCrash.ll | ||
2008-04-15-Byval.ll | ||
2008-06-02-GEPTailCrash.ll | ||
2008-11-23-NoaliasRet.ll | ||
2009-03-04-GEPNoalias.ll | ||
2009-10-13-AtomicModRef.ll | ||
2009-10-13-GEP-BaseNoAlias.ll | ||
2010-09-15-GEP-SignedArithmetic.ll | ||
2014-03-18-Maxlookup-reached.ll | ||
aligned-overread.ll | ||
args-rets-allocas-loads.ll | ||
assume.ll | ||
byval.ll | ||
cas.ll | ||
constant-over-index.ll | ||
cs-cs.ll | ||
dag.ll | ||
empty.ll | ||
featuretest.ll | ||
full-store-partial-alias.ll | ||
gcsetest.ll | ||
gep-alias.ll | ||
getmodrefinfo-cs-cs.ll | ||
global-size.ll | ||
intrinsics.ll | ||
invariant_load.ll | ||
memset_pattern.ll | ||
modref.ll | ||
must-and-partial.ll | ||
no-escape-call.ll | ||
noalias-bugs.ll | ||
noalias-geps.ll | ||
noalias-param.ll | ||
nocapture.ll | ||
phi-aa.ll | ||
phi-and-select.ll | ||
phi-spec-order.ll | ||
phi-speculation.ll | ||
pr18573.ll | ||
pure-const-dce.ll | ||
store-promote.ll | ||
tailcall-modref.ll | ||
underlying-value.ll | ||
unreachable-block.ll | ||
zext.ll |