search for: nullcheck

...n set of baggage that can inhibit optimization. (For example, if we can prove that a load would always succeed, 'volatile' prevents us from reordering the load or deleting it if it is dead.) So I propose to add an attribute to 'load' and 'store', which we can call, say, 'nullcheck', with the following additional semantics: - If the memory address is between zero and a target-defined value (i.e. the size of the zero page) the instruction is guaranteed to trap in a target-defined manner. - The optimizer may only delete or reorder nullcheck instructions if the...

...bit optimization. (For example, if we can prove > > that a load would always succeed, 'volatile' prevents us from reordering > > the load or deleting it if it is dead.) So I propose to add an attribute to > > 'load' and 'store', which we can call, say, 'nullcheck', with the following > > additional semantics: > > > > - If the memory address is between zero and a target-defined value (i.e. the > > size of the zero page) the instruction is guaranteed to trap in a > > target-defined manner. > > > > - The opti...

...lude: > - Dealing with the explosion of basic blocks that come up with > languages where almost every function call, implicit and explicit, can > raise exceptions. I saw this come up in a recent discussion about LLILC. One simple way to do this is to introduce a new intrinsic, like “llvm.nullcheck(x)” which symbolically represents the null check and bail out in one instruction - instead of the fully elaborated basic block representation (which slows everything down by increasing the height of the CFG). These null checks can be optimized away through standard techniques, and any remaining on...

Sanjoy, Joseph, and I will be hosting a BoF on using LLVM to build compilers for managed languages. We're curious to hear who's planning on attending and what topics you'd like to hear about. Depending on the expected audience, we're happy to do anything between a rough "what to expect getting started" to a down in the weeds working session on relevant optimization

Hi all, I would like to propose a mechanism that would allow LLVM to fold null pointer checks into "nearby" memory operations, subject to runtime support. This is related to but not exactly the same as a proposal floated by Peter Collingbourne earlier [1]. The obvious use cases are managed languages like Java, C# and Go that require a null check on pointers before they're used in