On Sun, Jun 06, 2021 at 08:17:40AM -0500, Segher Boessenkool wrote: > On Sat, Jun 05, 2021 at 09:43:33PM -0700, Paul E. McKenney wrote: > > So gcc might some day note a do-nothing asm and duplicate it for > > the sole purpose of collapsing the "then" and "else" clauses. I > > guess I need to keep my paranoia for the time being, then. :-/ > > Or a "do-something" asm, even. What it does is make sure it is executed > on the real machine exactly like on the abstract machine. That is how C > is defined, what a compiler *does*. > > The programmer does not have any direct control over the generated code. I am not looking for direct control, simply sufficient influence. ;-) > > Of course, there is no guarantee that gcc won't learn about > > assembler constants. :-/ > > I am not sure what you call an "assembler constant" here. But you can > be sure that GCC will not start doing anything here. GCC does not try > to understand what you wrote in an inline asm, it just fills in the > operands and that is all. It can do all the same things to it that it > can do to any other code of course: duplicate it, deduplicate it, > frobnicate it, etc. Apologies, that "assembler constants" should have been "assembler comments". Thanx, Paul
