[PM/AA] Hoist the AliasResult enum out of the AliasAnalysis class.

This will allow classes to implement the AA interface without deriving
from the class or referencing an internal enum of some other class as
their return types.

Also, to a pretty fundamental extent, concepts such as 'NoAlias',
'MayAlias', and 'MustAlias' are first class concepts in LLVM and we
aren't saving anything by scoping them heavily.

My mild preference would have been to use a scoped enum, but that
feature is essentially completely broken AFAICT. I'm extremely
disappointed. For example, we cannot through any reasonable[1] means
construct an enum class (or analog) which has scoped names but converts
to a boolean in order to test for the possibility of aliasing.

[1]: Richard Smith came up with a "solution", but it requires class
templates, and lots of boilerplate setting up the enumeration multiple
times. Something like Boost.PP could potentially bundle this up, but
even that would be quite painful and it doesn't seem realistically worth
it. The enum class solution would probably work without the need for
a bool conversion.

Differential Revision: http://reviews.llvm.org/D10495

llvm-svn: 240255

2 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index ae4b935d719..388ffd3a1c9 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -574,13 +574,13 @@ static bool MIsNeedChainEdge(AliasAnalysis *AA, const MachineFrameInfo *MFI,
   int64_t Overlapa = MMOa->getSize() + MMOa->getOffset() - MinOffset;
   int64_t Overlapb = MMOb->getSize() + MMOb->getOffset() - MinOffset;
 
-  AliasAnalysis::AliasResult AAResult =
+  AliasResult AAResult =
       AA->alias(MemoryLocation(MMOa->getValue(), Overlapa,
                                UseTBAA ? MMOa->getAAInfo() : AAMDNodes()),
                 MemoryLocation(MMOb->getValue(), Overlapb,
                                UseTBAA ? MMOb->getAAInfo() : AAMDNodes()));
 
-  return (AAResult != AliasAnalysis::NoAlias);
+  return (AAResult != NoAlias);
 }
 
 /// This recursive function iterates over chain deps of SUb looking for
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5fea52c9749..bc2e5f13d43 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13884,12 +13884,12 @@ bool DAGCombiner::isAlias(LSBaseSDNode *Op0, LSBaseSDNode *Op1) const {
         Op0->getSrcValueOffset() - MinOffset;
     int64_t Overlap2 = (Op1->getMemoryVT().getSizeInBits() >> 3) +
         Op1->getSrcValueOffset() - MinOffset;
-    AliasAnalysis::AliasResult AAResult =
+    AliasResult AAResult =
         AA.alias(MemoryLocation(Op0->getMemOperand()->getValue(), Overlap1,
                                 UseTBAA ? Op0->getAAInfo() : AAMDNodes()),
                  MemoryLocation(Op1->getMemOperand()->getValue(), Overlap2,
                                 UseTBAA ? Op1->getAAInfo() : AAMDNodes()));
-    if (AAResult == AliasAnalysis::NoAlias)
+    if (AAResult == NoAlias)
       return false;
   }