From: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> Date: Wed, 2 Feb 2011 16:37:02 +0000 > 1. there's no way to tell GCC that the inline assembly is a load > instruction and therefore it needs to schedule the following > instructions appropriately. Just add a dummy '"m" (pointer)' asm input argument to the inline asm statement. Just make sure "typeof(pointer)" has a size matching the size of the load your are performing. > 2. GCC will needlessly reload pointers from structures and other such > behaviour because it can't be told clearly what the inline assembly > is doing, so the inline asm needs to have a "memory" clobber. This behavior is correct, and in fact needed. Writing to chip registers can trigger changes to arbitrary main memory locations. > 3. It seems to misses out using the pre-index addressing, prefering to > create add/sub instructions prior to each inline assembly load/store. Yes, this is indeed a problem. But you really need that memory clobber there whether you like it or not, see above. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
