Add 'nonnull', a new parameter and return attribute which indicates that the pointer is not null. Instcombine will elide comparisons between these and null. Patch by Luqman Aden!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209185 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm-c/Core.h

@@ -165,7 +165,8 @@ typedef enum {
     LLVMStackProtectStrongAttribute = 1ULL<<33,
     LLVMCold = 1ULL << 34,
     LLVMOptimizeNone = 1ULL << 35,
-    LLVMInAllocaAttribute = 1ULL << 36
+    LLVMInAllocaAttribute = 1ULL << 36,
+    LLVMNonNullAttribute = 1ULL << 37
     */
 } LLVMAttribute;