Index: llvm/trunk/lib/Analysis/Loads.cpp
===================================================================
--- llvm/trunk/lib/Analysis/Loads.cpp
+++ llvm/trunk/lib/Analysis/Loads.cpp
@@ -210,50 +210,12 @@
   if (isDereferenceableAndAlignedPointer(V, Align, Size, DL, CtxI, DT))
     return true;
 
-  int64_t ByteOffset = 0;
-  Value *Base = V;
-  Base = GetPointerBaseWithConstantOffset(V, ByteOffset, DL);
-
-  if (ByteOffset < 0) // out of bounds
+  if (!ScanFrom)
     return false;
 
-  Type *BaseType = nullptr;
-  unsigned BaseAlign = 0;
-  if (const AllocaInst *AI = dyn_cast<AllocaInst>(Base)) {
-    // An alloca is safe to load from as load as it is suitably aligned.
-    BaseType = AI->getAllocatedType();
-    BaseAlign = AI->getAlignment();
-  } else if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
-    // Global variables are not necessarily safe to load from if they are
-    // interposed arbitrarily. Their size may change or they may be weak and
-    // require a test to determine if they were in fact provided.
-    if (!GV->isInterposable()) {
-      BaseType = GV->getType()->getElementType();
-      BaseAlign = GV->getAlignment();
-    }
-  }
-
-  PointerType *AddrTy = cast<PointerType>(V->getType());
-  uint64_t LoadSize = DL.getTypeStoreSize(AddrTy->getElementType());
-
-  // If we found a base allocated type from either an alloca or global variable,
-  // try to see if we are definitively within the allocated region. We need to
-  // know the size of the base type and the loaded type to do anything in this
-  // case.
-  if (BaseType && BaseType->isSized()) {
-    if (BaseAlign == 0)
-      BaseAlign = DL.getPrefTypeAlignment(BaseType);
-
-    if (Align <= BaseAlign) {
-      // Check if the load is within the bounds of the underlying object.
-      if (ByteOffset + LoadSize <= DL.getTypeAllocSize(BaseType) &&
-          ((ByteOffset % Align) == 0))
-        return true;
-    }
-  }
-
-  if (!ScanFrom)
+  if (Size.getBitWidth() > 64)
     return false;
+  const uint64_t LoadSize = Size.getZExtValue();
 
   // Otherwise, be a little bit aggressive by scanning the local block where we
   // want to check to see if the pointer is already being loaded or stored
@@ -302,7 +264,8 @@
       continue;
 
     // Handle trivial cases.
-    if (AccessedPtr == V)
+    if (AccessedPtr == V &&
+        LoadSize <= DL.getTypeStoreSize(AccessedTy))
       return true;
 
     if (AreEquivalentAddressValues(AccessedPtr->stripPointerCasts(), V) &&
Index: llvm/trunk/lib/Transforms/Scalar/SROA.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/SROA.cpp
+++ llvm/trunk/lib/Transforms/Scalar/SROA.cpp
@@ -1218,7 +1218,7 @@
       if (BBI->mayWriteToMemory())
         return false;
 
-    uint64_t Size = DL.getTypeStoreSizeInBits(LI->getType());
+    uint64_t Size = DL.getTypeStoreSize(LI->getType());
     MaxAlign = std::max(MaxAlign, LI->getAlignment());
     MaxSize = MaxSize.ult(Size) ? APInt(APWidth, Size) : MaxSize;
     HaveLoad = true;
Index: llvm/trunk/test/Transforms/SROA/addrspacecast.ll
===================================================================
--- llvm/trunk/test/Transforms/SROA/addrspacecast.ll
+++ llvm/trunk/test/Transforms/SROA/addrspacecast.ll
@@ -282,7 +282,9 @@
   ret void
 }
 
-@gv = external addrspace(1) global i64
+;; If this was external, we wouldn't be able to prove dereferenceability
+;; of the location.
+@gv = addrspace(1) global i64 zeroinitializer
 
 define void @select_addrspacecast_gv(i1 %a, i1 %b) {
 ; CHECK-LABEL: @select_addrspacecast_gv(
@@ -299,10 +301,11 @@
   ret void
 }
 
-; CHECK-LABEL: @select_addrspacecast_i8(
-; CHECK: [[SEL:%.*]] = select i1 undef, i8 undef, i8 undef
-; CHECK-NEXT: ret i8 [[SEL]]
 define i8 @select_addrspacecast_i8() {
+; CHECK-LABEL: @select_addrspacecast_i8(
+; CHECK-NEXT:    [[RET_SROA_SPECULATED:%.*]] = select i1 undef, i8 undef, i8 undef
+; CHECK-NEXT:    ret i8 [[RET_SROA_SPECULATED]]
+;
   %a = alloca i8
   %b = alloca i8