GitHub PushEvent at 2014-10-06 19:00:19
Repository: llvm
Actor: llvm-mirror
Payload: {"shas":[["27069a921a4d96cbee807d66375812ab0a70f08f","788c14eeffa2067e120409a238fa186a04f20a10@amd.com","Update documentation with link to Sea Islands documentation\n\ngit-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219134 91177308-0d34-0410-b5e6-96231b3b80d8","Matt Arsenault",true],["b9ce60ff09ce9ddc94862f72d94ed09e4c4a1b49","76a8e82c3bdc78a1f9490a34857cdee8b1b06a45@anl.gov","[BasicAA] Revert \"Revert r218714 - Make better use of zext and sign information.\"\n\nThis reverts r218944, which reverted r218714, plus a bug fix.\n\nDescription of the bug in r218714 (by Nick)\n\nThe original patch forgot to check if the Scale in VariableGEPIndex flipped the\nsign of the variable. The BasicAA pass iterates over the instructions in the\norder they appear in the function, and so BasicAliasAnalysis::aliasGEP is\ncalled with the variable it first comes across as parameter GEP1. Adding a\n%reorder label puts the definition of %a after %b so aliasGEP is called with %b\nas the first parameter and %a as the second. aliasGEP later calculates that %a\n== %b + 1 - %idxprom where %idxprom >= 0 (if %a was passed as the first\nparameter it would calculate %b == %a - 1 + %idxprom where %idxprom >= 0) -\nignoring that %idxprom is scaled by -1 here lead the patch to incorrectly\nconclude that %a > %b.\n\nRevised patch by Nick White, thanks! Thanks to Lang to isolating the bug.\nSlightly modified by me to add an early exit from the loop and avoid\nunnecessary, but expensive, function calls.\n\nOriginal commit message:\n\nTwo related things:\n\n 1. Fixes a bug when calculating the offset in GetLinearExpression. The code\n    previously used zext to extend the offset, so negative offsets were converted\n    to large positive ones.\n\n 2. Enhance aliasGEP to deduce that, if the difference between two GEP\n    allocations is positive and all the variables that govern the offset are also\n    positive (i.e. the offset is strictly after the higher base pointer), then\n    locations that fit in the gap between the two base pointers are NoAlias.\n\nPatch by Nick White!\n\ngit-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219135 91177308-0d34-0410-b5e6-96231b3b80d8","Hal Finkel",true]],"size":2,"ref":"refs/heads/master","head":"b9ce60ff09ce9ddc94862f72d94ed09e4c4a1b49"}