Jakob Stoklund Olesen 58e9ee85fd Teach SimplifyCFG about magic pointer constants. ...

Weird code sometimes uses pointer constants other than null. This patch
teaches SimplifyCFG to build switch instructions in those cases.

Code like this:

void f(const char *x) {
  if (!x)
    puts("null");
  else if ((uintptr_t)x == 1)
    puts("one");
  else if (x == (char*)2 || x == (char*)3)
    puts("two");
  else if ((intptr_t)x == 4)
    puts("four");
  else
    puts(x);
}

Now becomes a switch:

define void @f(i8* %x) nounwind ssp {
entry:
  %magicptr23 = ptrtoint i8* %x to i64            ; <i64> [#uses=1]
  switch i64 %magicptr23, label %if.else16 [
    i64 0, label %if.then
    i64 1, label %if.then2
    i64 2, label %if.then9
    i64 3, label %if.then9
    i64 4, label %if.then14
  ]

Note that LLVM's own DenseMap uses magic pointers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95439 91177308-0d34-0410-b5e6-96231b3b80d8

2010-02-05 22:03:18 +00:00

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2002-05-05-EmptyBlockMerge.ll

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2002-05-21-PHIElimination.ll

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2002-06-24-PHINode.ll

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2002-09-24-PHIAssertion.ll

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2003-03-07-DominateProblem.ll

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2003-08-05-InvokeCrash.ll

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2003-08-05-MishandleInvoke.ll

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2003-08-17-BranchFoldOrdering.ll

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2003-08-17-FoldSwitch-dbg.ll

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2003-08-17-FoldSwitch.ll

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2004-12-10-SimplifyCFGCrash.ll

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2005-06-16-PHICrash.ll

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2005-08-01-PHIUpdateFail.ll

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2005-08-03-PHIFactorCrash.ll

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2005-10-02-InvokeSimplify.ll

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2006-02-17-InfiniteUnroll.ll

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2006-10-19-UncondDiv.ll

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2006-10-29-InvokeCrash.ll

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2006-12-08-Ptr-ICmp-Branch.ll

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2007-11-22-InvokeNoUnwind.ll

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2007-12-21-Crash.ll

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2008-01-02-hoist-fp-add.ll

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2008-04-23-MergeMultipleResultRet.ll

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2008-04-27-MultipleReturnCrash.ll

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2008-05-16-PHIBlockMerge.ll

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2008-07-13-InfLoopMiscompile.ll

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2008-09-08-MultiplePred.ll

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2008-09-17-SpeculativeHoist.ll

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2008-10-03-SpeculativelyExecuteBeforePHI.ll

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2008-12-06-SingleEntryPhi.ll

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2008-12-16-DCECond.ll

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2009-01-18-PHIPropCrash.ll

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2009-01-19-UnconditionalTrappingConstantExpr.ll

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2009-03-05-Speculative-Hoist-Dbg.ll

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basictest.ll

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branch_fold_dbg.ll

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branch-branch-dbginfo.ll

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branch-cond-merge.ll

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branch-cond-prop.ll

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branch-fold-test.ll

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branch-fold.ll

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branch-phi-thread.ll

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BrUnwind.ll

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dbginfo.ll

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duplicate-phis.ll

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EqualPHIEdgeBlockMerge.ll

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hoist-common-code.dbg.ll

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hoist-common-code.ll

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HoistCode.ll

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invoke_unwind.ll

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iterative-simplify.ll

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MagicPointer.ll

Teach SimplifyCFG about magic pointer constants.

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noreturn-call.ll

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PhiBlockMerge2.ll

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PhiBlockMerge.ll

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PhiEliminate2.ll

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PhiEliminate.ll

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PhiNoEliminate.ll

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switch_formation.dbg.ll

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switch_thread.ll

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UnreachableEliminate.ll

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