Index: lib/IR/ConstantFold.cpp
===================================================================
--- lib/IR/ConstantFold.cpp
+++ lib/IR/ConstantFold.cpp
@@ -529,7 +529,10 @@
       // Try hard to fold cast of cast because they are often eliminable.
       if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
         return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
-    } else if (CE->getOpcode() == Instruction::GetElementPtr) {
+    } else if (CE->getOpcode() == Instruction::GetElementPtr &&
+               // Do not fold addrspacecast (gep 0, .., 0). It might make the
+               // addrspacecast uncanonicalized.
+               opc != Instruction::AddrSpaceCast) {
       // If all of the indexes in the GEP are null values, there is no pointer
       // adjustment going on.  We might as well cast the source pointer.
       bool isAllNull = true;
Index: lib/IR/Constants.cpp
===================================================================
--- lib/IR/Constants.cpp
+++ lib/IR/Constants.cpp
@@ -1698,6 +1698,19 @@
   assert(CastInst::castIsValid(Instruction::AddrSpaceCast, C, DstTy) &&
          "Invalid constantexpr addrspacecast!");
 
+  // Canonicalize addrspacecasts between different pointer types by first
+  // bitcasting the pointer type and then converting the address space.
+  PointerType *SrcScalarTy = cast<PointerType>(C->getType()->getScalarType());
+  PointerType *DstScalarTy = cast<PointerType>(DstTy->getScalarType());
+  Type *DstElemTy = DstScalarTy->getElementType();
+  if (SrcScalarTy->getElementType() != DstElemTy) {
+    Type *MidTy = PointerType::get(DstElemTy, SrcScalarTy->getAddressSpace());
+    if (VectorType *VT = dyn_cast<VectorType>(DstTy)) {
+      // Handle vectors of pointers.
+      MidTy = VectorType::get(MidTy, VT->getNumElements());
+    }
+    C = getBitCast(C, MidTy);
+  }
   return getFoldedCast(Instruction::AddrSpaceCast, C, DstTy);
 }
 
Index: lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1919,8 +1919,10 @@
   Type *DestElemTy = DestTy->getElementType();
   if (SrcTy->getElementType() != DestElemTy) {
     Type *MidTy = PointerType::get(DestElemTy, SrcTy->getAddressSpace());
-    if (CI.getType()->isVectorTy()) // Handle vectors of pointers.
-      MidTy = VectorType::get(MidTy, CI.getType()->getVectorNumElements());
+    if (VectorType *VT = dyn_cast<VectorType>(CI.getType())) {
+      // Handle vectors of pointers.
+      MidTy = VectorType::get(MidTy, VT->getNumElements());
+    }
 
     Value *NewBitCast = Builder->CreateBitCast(Src, MidTy);
     return new AddrSpaceCastInst(NewBitCast, CI.getType());
Index: test/Assembler/addrspacecast-alias.ll
===================================================================
--- test/Assembler/addrspacecast-alias.ll
+++ test/Assembler/addrspacecast-alias.ll
@@ -4,4 +4,4 @@
 
 @i = internal addrspace(1) global i8 42
 @ia = alias internal addrspacecast (i8 addrspace(1)* @i to i8 addrspace(2)* addrspace(3)*)
-; CHECK: @ia =  alias internal addrspacecast (i8 addrspace(1)* @i to i8 addrspace(2)* addrspace(3)*)
+; CHECK: @ia = alias internal addrspacecast (i8 addrspace(2)* addrspace(1)* bitcast (i8 addrspace(1)* @i to i8 addrspace(2)* addrspace(1)*) to i8 addrspace(2)* addrspace(3)*)
Index: test/CodeGen/NVPTX/access-non-generic.ll
===================================================================
--- test/CodeGen/NVPTX/access-non-generic.ll
+++ test/CodeGen/NVPTX/access-non-generic.ll
@@ -74,13 +74,13 @@
   ret float %sum5
 }
 
-; Verifies nvptx-favor-non-generic keeps addrspacecasts between pointers of
-; different element types.
+; When hoisting an addrspacecast between different pointer types, replace the
+; addrspacecast with a bitcast.
 define i32 @ld_int_from_float() {
 ; IR-LABEL: @ld_int_from_float
-; IR: addrspacecast
+; IR: load i32 addrspace(3)* bitcast (float addrspace(3)* @scalar to i32 addrspace(3)*)
 ; PTX-LABEL: ld_int_from_float(
-; PTX: cvta.shared.u{{(32|64)}}
+; PTX: ld.shared.u{{(32|64)}}
   %1 = load i32* addrspacecast(float addrspace(3)* @scalar to i32*), align 4
   ret i32 %1
 }
Index: test/Other/constant-fold-gep.ll
===================================================================
--- test/Other/constant-fold-gep.ll
+++ test/Other/constant-fold-gep.ll
@@ -457,7 +457,7 @@
   %p = getelementptr inbounds i8* addrspacecast ([4 x i8] addrspace(12)* @p12 to i8*),
                                   i32 2
   ret i8* %p
-; OPT: ret i8* getelementptr (i8* addrspacecast ([4 x i8] addrspace(12)* @p12 to i8*), i32 2)
+; OPT: ret i8* getelementptr (i8* addrspacecast (i8 addrspace(12)* getelementptr inbounds ([4 x i8] addrspace(12)* @p12, i32 0, i32 0) to i8*), i32 2)
 }
 
 define i8* @same_addrspace() nounwind noinline {
Index: test/Transforms/InstCombine/constant-fold-address-space-pointer.ll
===================================================================
--- test/Transforms/InstCombine/constant-fold-address-space-pointer.ll
+++ test/Transforms/InstCombine/constant-fold-address-space-pointer.ll
@@ -230,3 +230,13 @@
   %b = load i32 addrspace(1)* %a, align 4
   ret i32 %b
 }
+
+@shared_mem = external addrspace(3) global [0 x i8]
+
+define float @canonicalize_addrspacecast(i32 %i) {
+; CHECK-LABEL: @canonicalize_addrspacecast
+; CHECK-NEXT: getelementptr inbounds float* addrspacecast (float addrspace(3)* bitcast ([0 x i8] addrspace(3)* @shared_mem to float addrspace(3)*) to float*), i32 %i
+  %p = getelementptr inbounds float* addrspacecast ([0 x i8] addrspace(3)* @shared_mem to float*), i32 %i
+  %v = load float* %p
+  ret float %v
+}