search for: was_interrupted

Responding to the original email... On Sun, Jan 3, 2010 at 10:10 PM, James Y Knight <foom at fuhm.net> wrote: > In working on an LLVM backend for SBCL (a lisp compiler), there are > certain sequences of code that must be atomic with regards to async > signals. Can you define exactly what 'atomic with regards to async signals' this entails? Your descriptions led me to think

...* %obj_header ;; store obj type (5) in header word %obj_len = getelementptr i64* %obj, i64 1 store i64 2, i64* %obj_len ;; store obj length (2) in length slot ...etc... ;; Check if we were interrupted: %res = call i64 @llvm.atomic.load.sub.i64.p0i64(i64* @pseudo_atomic, i64 1) %was_interrupted = icmp eq i64 %res, 1 br i1 %was_interrupted, label %do-interruption, label %continue continue: ret i64* %obj do-interruption: call void @do_pending_interrupt() br label %continue } A signal handler will check the thread-local @pseudo_atomic variable: if it was already set it will...

In working on an LLVM backend for SBCL (a lisp compiler), there are certain sequences of code that must be atomic with regards to async signals. So, for example, on x86, a single SUB on a memory location should be used, not a load/sub/store sequence. LLVM's IR doesn't currently have any way to express this kind of constraint (...and really, that's essentially impossible since