Make LocationSize a proper Optional type; NFC

This is the second in a series of changes intended to make
https://reviews.llvm.org/D44748 more easily reviewable. Please see that
patch for more context. The first change being r344012.

Since I was requested to do all of this with post-commit review, this is
about as small as I can make this patch.

This patch makes LocationSize into an actual type that wraps a uint64_t;
users are required to call getValue() in order to get the size now. If
the LocationSize has an Unknown size (e.g. if LocSize ==
MemoryLocation::UnknownSize), getValue() will assert.

This also adds DenseMap specializations for LocationInfo, which required
taking two more values from the set of values LocationInfo can
represent. Hence, heavy users of multi-exabyte arrays or structs may
observe slightly lower-quality code as a result of this change.

The intent is for getValue()s to be very close to a corresponding
hasValue() (which is often spelled `!= MemoryLocation::UnknownSize`).
Sadly, small diff context appears to crop that out sometimes, and the
last change in DSE does require a bit of nonlocal reasoning about
control-flow. :/

This also removes an assert, since it's now redundant with the assert in
getValue().

llvm-svn: 344013
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 6d4ac96..072a50a 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1023,8 +1023,8 @@
       MaybeV2Size == MemoryLocation::UnknownSize)
     return MayAlias;
 
-  const uint64_t V1Size = MaybeV1Size;
-  const uint64_t V2Size = MaybeV2Size;
+  const uint64_t V1Size = MaybeV1Size.getValue();
+  const uint64_t V2Size = MaybeV2Size.getValue();
 
   ConstantInt *C1 =
       dyn_cast<ConstantInt>(GEP1->getOperand(GEP1->getNumOperands() - 1));
@@ -1188,7 +1188,7 @@
       !GEPOp->isInBounds())
     return false;
 
-  const uint64_t ObjectAccessSize = MaybeObjectAccessSize;
+  const uint64_t ObjectAccessSize = MaybeObjectAccessSize.getValue();
 
   // We need the object to be an alloca or a globalvariable, and want to know
   // the offset of the pointer from the object precisely, so no variable
@@ -1352,7 +1352,7 @@
   if (GEP1BaseOffset != 0 && DecompGEP1.VarIndices.empty()) {
     if (GEP1BaseOffset >= 0) {
       if (V2Size != MemoryLocation::UnknownSize) {
-        if ((uint64_t)GEP1BaseOffset < V2Size)
+        if ((uint64_t)GEP1BaseOffset < V2Size.getValue())
           return PartialAlias;
         return NoAlias;
       }
@@ -1367,7 +1367,7 @@
       // stripped a gep with negative index ('gep <ptr>, -1, ...).
       if (V1Size != MemoryLocation::UnknownSize &&
           V2Size != MemoryLocation::UnknownSize) {
-        if (-(uint64_t)GEP1BaseOffset < V1Size)
+        if (-(uint64_t)GEP1BaseOffset < V1Size.getValue())
           return PartialAlias;
         return NoAlias;
       }
@@ -1417,8 +1417,9 @@
     // two locations do not alias.
     uint64_t ModOffset = (uint64_t)GEP1BaseOffset & (Modulo - 1);
     if (V1Size != MemoryLocation::UnknownSize &&
-        V2Size != MemoryLocation::UnknownSize && ModOffset >= V2Size &&
-        V1Size <= Modulo - ModOffset)
+        V2Size != MemoryLocation::UnknownSize &&
+        ModOffset >= V2Size.getValue() &&
+        V1Size.getValue() <= Modulo - ModOffset)
       return NoAlias;
 
     // If we know all the variables are positive, then GEP1 >= GEP1BasePtr.
@@ -1426,7 +1427,7 @@
     // don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr.
     if (AllPositive && GEP1BaseOffset > 0 &&
         V2Size != MemoryLocation::UnknownSize &&
-        V2Size <= (uint64_t)GEP1BaseOffset)
+        V2Size.getValue() <= (uint64_t)GEP1BaseOffset)
       return NoAlias;
 
     if (constantOffsetHeuristic(DecompGEP1.VarIndices, V1Size, V2Size,
@@ -1715,9 +1716,11 @@
   // side, then we know such behavior is undefined and can assume no alias.
   bool NullIsValidLocation = NullPointerIsDefined(&F);
   if ((V1Size != MemoryLocation::UnknownSize &&
-       isObjectSmallerThan(O2, V1Size, DL, TLI, NullIsValidLocation)) ||
+       isObjectSmallerThan(O2, V1Size.getValue(), DL, TLI,
+                           NullIsValidLocation)) ||
       (V2Size != MemoryLocation::UnknownSize &&
-       isObjectSmallerThan(O1, V2Size, DL, TLI, NullIsValidLocation)))
+       isObjectSmallerThan(O1, V2Size.getValue(), DL, TLI,
+                           NullIsValidLocation)))
     return NoAlias;
 
   // Check the cache before climbing up use-def chains. This also terminates
@@ -1777,8 +1780,8 @@
   if (O1 == O2)
     if (V1Size != MemoryLocation::UnknownSize &&
         V2Size != MemoryLocation::UnknownSize &&
-        (isObjectSize(O1, V1Size, DL, TLI, NullIsValidLocation) ||
-         isObjectSize(O2, V2Size, DL, TLI, NullIsValidLocation)))
+        (isObjectSize(O1, V1Size.getValue(), DL, TLI, NullIsValidLocation) ||
+         isObjectSize(O2, V2Size.getValue(), DL, TLI, NullIsValidLocation)))
       return AliasCache[Locs] = PartialAlias;
 
   // Recurse back into the best AA results we have, potentially with refined
@@ -1868,8 +1871,8 @@
       MaybeV2Size == MemoryLocation::UnknownSize)
     return false;
 
-  const uint64_t V1Size = MaybeV1Size;
-  const uint64_t V2Size = MaybeV2Size;
+  const uint64_t V1Size = MaybeV1Size.getValue();
+  const uint64_t V2Size = MaybeV2Size.getValue();
 
   const VariableGEPIndex &Var0 = VarIndices[0], &Var1 = VarIndices[1];
 
diff --git a/llvm/lib/Analysis/CFLAndersAliasAnalysis.cpp b/llvm/lib/Analysis/CFLAndersAliasAnalysis.cpp
index db350e2..b43b48e 100644
--- a/llvm/lib/Analysis/CFLAndersAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/CFLAndersAliasAnalysis.cpp
@@ -561,8 +561,8 @@
           MaybeRHSSize == MemoryLocation::UnknownSize)
         return true;
 
-      const uint64_t LHSSize = MaybeLHSSize;
-      const uint64_t RHSSize = MaybeRHSSize;
+      const uint64_t LHSSize = MaybeLHSSize.getValue();
+      const uint64_t RHSSize = MaybeRHSSize.getValue();
 
       for (const auto &OVal : make_range(RangePair)) {
         // Be conservative about UnknownOffset
diff --git a/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp b/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
index 7bea994..61f6254 100644
--- a/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
@@ -43,8 +43,12 @@
   if (SE.getEffectiveSCEVType(AS->getType()) ==
       SE.getEffectiveSCEVType(BS->getType())) {
     unsigned BitWidth = SE.getTypeSizeInBits(AS->getType());
-    APInt ASizeInt(BitWidth, LocA.Size);
-    APInt BSizeInt(BitWidth, LocB.Size);
+    APInt ASizeInt(BitWidth, LocA.Size.hasValue()
+                                 ? LocA.Size.getValue()
+                                 : MemoryLocation::UnknownSize);
+    APInt BSizeInt(BitWidth, LocB.Size.hasValue()
+                                 ? LocB.Size.getValue()
+                                 : MemoryLocation::UnknownSize);
 
     // Compute the difference between the two pointers.
     const SCEV *BA = SE.getMinusSCEV(BS, AS);