Am Wed, 22 Jan 2014 00:28:32 +0000 schrieb "Mike" <n...@none.com>:
> > "So what's the question, Mike?" I hear you say: > 1. Is this just one of the consequences of using -O2/-O3, and I > should just suck it up and deal with it? > 2. Is this potentially a bug in the GCC backend? > 3. Is this potentially a bug in GDC or the DMD frontend? > > Thanks for the help, > Mike I can only guess, but this looks like another 'volatile' problem. You'd have to post the ASM of the optimized version somewhere, and probably the output of -fdump-tree-optimized for the optimized version. But anyway, I guess it inlines 'SendCommand' and then thinks you're not using the message and probably completely optimizes the call away. Then it sees you're never using message and removes the rest of your code. If SendCommand was written in D you'd have to mark the target of the copy volatile (or shared). But I'm not sure how this applies to the inline asm though. In C you have asm volatile, but I never used that. This answer seems to state that you have to use asm volatile: http://stackoverflow.com/a/5057270/471401 So the questions for Iain: * should we mark all inline ASM blocks as volatile? * shared can't replace volatile in this case as `shared asm{...}` isn't valid * Should we add some GDC specific way to mark extended ASM blocks as volatile? As DMD doesn't optimize ASM blocks at all there's probably no need for a standard solution?
