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Make ModRefBehavior a lattice. Use this to clean up AliasAnalysis

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chaining and simplify FunctionAttrs' GetModRefBehavior logic.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118660 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-11-10 01:02:18 +00:00
parent cc8d10e1a8
commit 42c31a7073
8 changed files with 71 additions and 74 deletions
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14
lib/Analysis/BasicAliasAnalysis.cpp
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@ -595,7 +595,7 @@ BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
Min = OnlyReadsMemory;
// The AliasAnalysis base class has some smarts, lets use them.
return std::min(AliasAnalysis::getModRefBehavior(CS), Min);
return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
}
/// getModRefBehavior - Return the behavior when calling the given function.
@ -613,12 +613,14 @@ BasicAliasAnalysis::getModRefBehavior(const Function *F) {
#undef GET_INTRINSIC_MODREF_BEHAVIOR
}
ModRefBehavior Min = UnknownModRefBehavior;
// If the function declares it only reads memory, go with that.
if (F->onlyReadsMemory())
return OnlyReadsMemory;
Min = OnlyReadsMemory;
// Otherwise be conservative.
return AliasAnalysis::getModRefBehavior(F);
return ModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min);
}
/// getModRefInfo - Check to see if the specified callsite can clobber the
@ -671,6 +673,8 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
return NoModRef;
}
ModRefResult Min = ModRef;
// Finally, handle specific knowledge of intrinsics.
const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
if (II != 0)
@ -686,7 +690,7 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
if (isNoAlias(Location(Dest, Len), Loc)) {
if (isNoAlias(Location(Src, Len), Loc))
return NoModRef;
return Ref;
Min = Ref;
}
break;
}
@ -745,7 +749,7 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
}
// The AliasAnalysis base class has some smarts, lets use them.
return AliasAnalysis::getModRefInfo(CS, Loc);
return ModRefResult(AliasAnalysis::getModRefInfo(CS, Loc) & Min);
}
/// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction