Also use gep inbounds nuw for index projections

Author: nikic

Diff for: compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -423,7 +423,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
             layout.size
         };
 
-        let llval = bx.inbounds_gep(bx.cx().backend_type(layout), self.val.llval, &[llindex]);
+        let llval = bx.inbounds_nuw_gep(bx.cx().backend_type(layout), self.val.llval, &[llindex]);
         let align = self.val.align.restrict_for_offset(offset);
         PlaceValue::new_sized(llval, align).with_type(layout)
     }

Diff for: tests/codegen/gep-index.rs

@@ -11,7 +11,7 @@ struct Foo(i32, i32);
 // CHECK-LABEL: @index_on_struct(
 #[no_mangle]
 fn index_on_struct(a: &[Foo], index: usize) -> &Foo {
-    // CHECK: getelementptr inbounds %Foo, ptr %a.0, {{i64|i32}} %index
+    // CHECK: getelementptr inbounds{{( nuw)?}} %Foo, ptr %a.0, {{i64|i32}} %index
     &a[index]
 }
 
@@ -25,7 +25,7 @@ fn offset_on_struct(a: *const Foo, index: usize) -> *const Foo {
 // CHECK-LABEL: @index_on_i32(
 #[no_mangle]
 fn index_on_i32(a: &[i32], index: usize) -> &i32 {
-    // CHECK: getelementptr inbounds i32, ptr %a.0, {{i64|i32}} %index
+    // CHECK: getelementptr inbounds{{( nuw)?}} i32, ptr %a.0, {{i64|i32}} %index
     &a[index]
 }