Fix asserts when linking wrong address space declarations

[efriedma]

LGTM

The only edge case I'm concerned about is that If you link together two modules, and neither has a definition, we just arbitrarily choose an address-space. But the AsmPrinter should be able to handle that, I guess.

[arsenm]

r342858

lib/Linker/IRMover.cpp

if (!ShouldLink && ForAlias)
     NewGV->setLinkage(GlobalValue::InternalLinkage);
 
   Constant *C = NewGV;
   // Only create a bitcast if necessary. In particular, with
   // DebugTypeODRUniquing we may reach metadata in the destination module
   // containing a GV from the source module, in which case SGV will be
   // the same as DGV and NewGV, and TypeMap.get() will assert since it
   // assumes it is being invoked on a type in the source module.
-  if (DGV && NewGV != SGV)
-    C = ConstantExpr::getBitCast(NewGV, TypeMap.get(SGV->getType()));
+  if (DGV && NewGV != SGV) {
+    C = ConstantExpr::getPointerBitCastOrAddrSpaceCast(
+      NewGV, TypeMap.get(SGV->getType()));
+  }
 
   if (DGV && NewGV != DGV) {
-    DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, DGV->getType()));
+    DGV->replaceAllUsesWith(
+      ConstantExpr::getPointerBitCastOrAddrSpaceCast(NewGV, DGV->getType()));
     DGV->eraseFromParent();
   }
 
   return C;
 }
 
 /// Update the initializers in the Dest module now that all globals that may be
 /// referenced are in Dest.

test/Linker/Inputs/wrong-addrspace-gv-declaration.ll

+@is_really_as1_gv = addrspace(1) global i32 0, align 4
+@is_really_as1_gv_other_type = addrspace(1) global float 4.0, align 4

test/Linker/wrong-addrspace-gv-declaration.ll

+; RUN: llvm-link %s %p/Inputs/wrong-addrspace-gv-declaration.ll -S | FileCheck %s
+; RUN: llvm-link %p/Inputs/wrong-addrspace-gv-declaration.ll %s -S | FileCheck %s
+
+; The address space is declared incorrectly here, so an addrspacecast
+; is needed to link.
+
+@is_really_as1_gv = external global i32
+@is_really_as1_gv_other_type = external global i32
+
+; CHECK-LABEL: @foo(
+; CHECK: %load0 = load volatile i32, i32* addrspacecast (i32 addrspace(1)* @is_really_as1_gv to i32*), align 4
+; CHECK: %load1 = load volatile i32, i32* addrspacecast (i32 addrspace(1)* bitcast (float addrspace(1)* @is_really_as1_gv_other_type to i32 addrspace(1)*) to i32*), align 4
+define void @foo() {
+  %load0 = load volatile i32, i32* @is_really_as1_gv, align 4
+  %load1 = load volatile i32, i32* @is_really_as1_gv_other_type, align 4
+  ret void
+}