ENH: Use memcpy and swap order

seberg · seberg · commit c176234bc697 · 2023-07-31T17:59:09.000+02:00
Not sure this makes a difference, but we check for memory overlap
so `memmov` isn't necessary and if the compiler keeps the order
intact, we want the `memcpy` path to be the hot one.
diff --git a/numpy/core/src/multiarray/item_selection.c b/numpy/core/src/multiarray/item_selection.c
@@ -1088,16 +1088,17 @@ PyArray_Choose(PyArrayObject *ip, PyObject *op, PyArrayObject *out,
                 break;
             }
         }
-        if (cast_info.func != NULL) {
+        if (cast_info.func == NULL) {
+            /* We ensure memory doesn't overlap, so can use memcpy */
+            memcpy(ret_data, PyArray_MultiIter_DATA(multi, mi), elsize);
+        }
+        else {
             char *args[2] = {PyArray_MultiIter_DATA(multi, mi), ret_data};
             if (cast_info.func(&cast_info.context, args, &one,
                                 transfer_strides, cast_info.auxdata) < 0) {
                 goto fail;
             }
         }
-        else {
-            memmove(ret_data, PyArray_MultiIter_DATA(multi, mi), elsize);
-        }
         ret_data += elsize;
         PyArray_MultiIter_NEXT(multi);
     }

Original file line number	Diff line number	Diff line change
`@@ -1088,16 +1088,17 @@ PyArray_Choose(PyArrayObject ip, PyObject op, PyArrayObject *out,`
`1088`	`1088`	`break;`
`1089`	`1089`	`}`
`1090`	`1090`	`}`
`1091`		`- if (cast_info.func != NULL) {`
	`1091`	`+ if (cast_info.func == NULL) {`
	`1092`	`+ /* We ensure memory doesn't overlap, so can use memcpy */`
	`1093`	`+ memcpy(ret_data, PyArray_MultiIter_DATA(multi, mi), elsize);`
	`1094`	`+ }`
	`1095`	`+ else {`
`1092`	`1096`	`char *args[2] = {PyArray_MultiIter_DATA(multi, mi), ret_data};`
`1093`	`1097`	`if (cast_info.func(&cast_info.context, args, &one,`
`1094`	`1098`	`transfer_strides, cast_info.auxdata) < 0) {`
`1095`	`1099`	`goto fail;`
`1096`	`1100`	`}`
`1097`	`1101`	`}`
`1098`		`- else {`
`1099`		`- memmove(ret_data, PyArray_MultiIter_DATA(multi, mi), elsize);`
`1100`		`- }`
`1101`	`1102`	`ret_data += elsize;`
`1102`	`1103`	`PyArray_MultiIter_NEXT(multi);`
`1103`	`1104`	`}`