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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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18
include/llvm/Analysis/AliasAnalysis.h
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@ -175,6 +175,9 @@ public:
///
enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 };
/// These values define additional bits used to define the
/// ModRefBehavior values.
enum { Nowhere = 0, ArgumentPointees = 4, Anywhere = 8 | ArgumentPointees };
/// ModRefBehavior - Summary of how a function affects memory in the program.
/// Loads from constant globals are not considered memory accesses for this
@ -187,20 +190,20 @@ public:
/// This property corresponds to the GCC 'const' attribute.
/// This property corresponds to the LLVM IR 'readnone' attribute.
/// This property corresponds to the IntrNoMem LLVM intrinsic flag.
DoesNotAccessMemory,
DoesNotAccessMemory = Nowhere | NoModRef,
/// AccessesArgumentsReadonly - This function loads through function
/// arguments and does not perform any non-local stores or volatile
/// loads.
///
/// This property corresponds to the IntrReadArgMem LLVM intrinsic flag.
AccessesArgumentsReadonly,
AccessesArgumentsReadonly = ArgumentPointees | Ref,
/// AccessesArguments - This function accesses function arguments in well
/// known (possibly volatile) ways, but does not access any other memory.
///
/// This property corresponds to the IntrReadWriteArgMem LLVM intrinsic flag.
AccessesArguments,
AccessesArguments = ArgumentPointees | ModRef,
/// OnlyReadsMemory - This function does not perform any non-local stores or
/// volatile loads, but may read from any memory location.
@ -208,11 +211,11 @@ public:
/// This property corresponds to the GCC 'pure' attribute.
/// This property corresponds to the LLVM IR 'readonly' attribute.
/// This property corresponds to the IntrReadMem LLVM intrinsic flag.
OnlyReadsMemory,
OnlyReadsMemory = Anywhere | Ref,
/// UnknownModRefBehavior - This indicates that the function could not be
/// classified into one of the behaviors above.
UnknownModRefBehavior
UnknownModRefBehavior = Anywhere | ModRef
};
/// getModRefBehavior - Return the behavior when calling the given call site.
@ -270,12 +273,9 @@ public:
/// true. For use when the call site is not known.
///
static bool onlyReadsMemory(ModRefBehavior MRB) {
return MRB == DoesNotAccessMemory ||
MRB == AccessesArgumentsReadonly ||
MRB == OnlyReadsMemory;
return !(MRB & Mod);
}
/// getModRefInfo - Return information about whether or not an instruction may
/// read or write the specified memory location. An instruction
/// that doesn't read or write memory may be trivially LICM'd for example.