From: Nadav Amit > Sent: 17 May 2018 17:14 > This patch-set deals with an interesting yet stupid problem: kernel code > that does not get inlined despite its simplicity. There are several > causes for this behavior: "cold" attribute on __init, different function > optimization levels; conditional constant computations based on > __builtin_constant_p(); and finally large inline assembly blocks. > > This patch-set deals with the inline assembly problem. I separated these > patches from the others (that were sent in the RFC) for easier > inclusion. > > The problem with inline assembly is that inline assembly is often used > by the kernel for things that are other than code - for example, > assembly directives and data. GCC however is oblivious to the content of > the blocks and assumes their cost in space and time is proportional to > the number of the perceived assembly "instruction", according to the > number of newlines and semicolons. Alternatives, paravirt and other > mechanisms are affected, causing code not to be inlined, and degrading > compilation quality in general. > > The solution that this patch-set carries for this problem is to create > an assembly macro, and then call it from the inline assembly block. As > a result, the compiler sees a single "instruction" and assigns the more > appropriate cost to the code. In addition, this patch-set removes > unneeded new-lines from common x86 inline asm's, which "confuse" GCC > heuristics. Can't you get the same effect by using always_inline ? David -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
