Thank you very much. Those first 2 Github links are very helpful. You mentioned it will be easier to use gc compiler's SSA representation. By what commands can I get that SSA representation and is there any documentation about the use of that representation.
On Sunday, December 18, 2016 at 10:37:55 PM UTC+5:30, Alan Donovan wrote: > > On 17 December 2016 at 23:54, <akshans...@gmail.com <javascript:>> wrote: > >> For each instruction in any BasicBlock I want to know the type of >> instruction, the variables used in that instruction. [...] Just one line >> of the program corresponds to multiple instructions. Is there some >> documentation as to how these instructions are constructed for a line of >> code so that I can decode these instructions for any general program’s SSA. >> > > The SSA package defines a minimal instruction set sufficient to express > the semantics of any Go program. It simplifies the program in certain ways, > such as: > - replacing many local variable defs and uses by direct graph edges > - reducing structured control flow with unstructured jumps > - expanding out the effects of "embedding" on field and method selections > - simplifying variadic calls with explicit slice operations > - defining closures for function literals with free variables. > However, it does not "lower" the core data types of Go (slices, channels, > etc) to simpler ones, so the sequence of SSA instructions generated for any > source construct should be quite intuitive. > > For examples of how to use the SSA form, take a look at the go/pointer > package that lives alongside go/ssa. It processes all the instructions > within each function to build and then solve an interprocedural system of > constraints: > > https://github.com/golang/tools/blob/master/go/pointer/gen.go#L934 > > Alternatively, look at the core function of the interpreter used for > testing the SSA construction algorithm. It visits each instruction in turn > and simulates its dynamic semantics: > > https://github.com/golang/tools/blob/master/go/ssa/interp/interp.go#L192 > > > > Also, I want to know the variables which are shared bw any goroutines or >> not. >> > > To answer this question precisely you need an "escape analysis", such > J.D.Choi et al.'s "Escape Analysis for Java" which classifies each variable > into one of three kinds: local variables, heap variables local to a single > thread, and shared variables. > > Building an escape analysis is a significant undertaking---similar to and > about as complex as the analysis done by the go/pointer package. You can > answer this question simply but very conservatively by assuming that all > heap variables (Alloc{Heap:true}) are shared by multiple goroutines. > > > >> All the instructions where one particular variable is being defined or >> used. >> > > Each local ssa.Value (such as an add instruction, BinaryOp{Op: ADD}) has a > set of edges (Referrers) to each place it is used. > For all other values (e.g. globals) you need to do a pass over the whole > program to find all references. > > > I need these infos because my aim is to implement the CSSA based SAT >> encoding for a program as mentioned on page 7 of this paper ( >> https://goo.gl/pdXuoe). >> > > That paper describes a hybrid static/dynamic analysis, which means it > needs to relate facts about a particular concrete execution of a program > with facts about a static abstraction of the same program. You will find > it easier to implement if you use as much common infrastructure as possible > for the two analysis, which means using the gc compiler's SSA > representation instead of the one in golang.org/x/tools/go/ssa. > > I don't wish to discourage you, but if this is your aim, I must warn you > that basic usage of the go/ssa package is like walking from the parking lot > to the trailhead, and you still have mountains to climb. > > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
