Index: llvm/trunk/lib/IR/DataLayout.cpp
===================================================================
--- llvm/trunk/lib/IR/DataLayout.cpp
+++ llvm/trunk/lib/IR/DataLayout.cpp
@@ -378,7 +378,10 @@
       }
       break;
     case 'S': { // Stack natural alignment.
-      StackNaturalAlign = MaybeAlign(inBytes(getInt(Tok)));
+      uint64_t Alignment = inBytes(getInt(Tok));
+      if (Alignment != 0 && !llvm::isPowerOf2_64(Alignment))
+        report_fatal_error("Alignment is neither 0 nor a power of 2");
+      StackNaturalAlign = MaybeAlign(Alignment);
       break;
     }
     case 'F': {
@@ -394,7 +397,10 @@
                            "datalayout string");
       }
       Tok = Tok.substr(1);
-      FunctionPtrAlign = MaybeAlign(inBytes(getInt(Tok)));
+      uint64_t Alignment = inBytes(getInt(Tok));
+      if (Alignment != 0 && !llvm::isPowerOf2_64(Alignment))
+        report_fatal_error("Alignment is neither 0 nor a power of 2");
+      FunctionPtrAlign = MaybeAlign(Alignment);
       break;
     }
     case 'P': { // Function address space.
Index: llvm/trunk/test/Assembler/datalayout-invalid-function-ptr-alignment.ll
===================================================================
--- llvm/trunk/test/Assembler/datalayout-invalid-function-ptr-alignment.ll
+++ llvm/trunk/test/Assembler/datalayout-invalid-function-ptr-alignment.ll
@@ -0,0 +1,5 @@
+; RUN: not llvm-as %s 2>&1 | FileCheck %s
+
+; CHECK: LLVM ERROR: Alignment is neither 0 nor a power of 2
+
+target datalayout = "Fi24"
Index: llvm/trunk/test/Assembler/datalayout-invalid-stack-natural-alignment.ll
===================================================================
--- llvm/trunk/test/Assembler/datalayout-invalid-stack-natural-alignment.ll
+++ llvm/trunk/test/Assembler/datalayout-invalid-stack-natural-alignment.ll
@@ -0,0 +1,5 @@
+; RUN: not llvm-as %s 2>&1 | FileCheck %s
+
+; CHECK: LLVM ERROR: Alignment is neither 0 nor a power of 2
+
+target datalayout = "S24"
Index: llvm/trunk/test/Bitcode/invalid-functionptr-align.ll
===================================================================
--- llvm/trunk/test/Bitcode/invalid-functionptr-align.ll
+++ llvm/trunk/test/Bitcode/invalid-functionptr-align.ll
@@ -0,0 +1,5 @@
+; Bitcode with invalid function pointer alignment.
+
+; RUN: not llvm-dis %s.bc -o - 2>&1 | FileCheck %s
+
+CHECK: LLVM ERROR: Alignment is neither 0 nor a power of 2