AbstractInterpreter: refactor the lifetimes of OptimizationState …

…and `IRCode`

This commit limits the lifetimes of `OptimizationState` and `IRCode`
for a more dataflow clarity. It also avoids duplicated calls of `ir_to_codeinf!`.

Note that external `AbstractInterpreter`s can still extend their
lifetimes to cache additional information, as described by this
newly added documentation of `finish!`:

>     finish!(interp::AbstractInterpreter,
>         opt::OptimizationState, ir::IRCode, caller::InferenceResult)
>
> Runs post-Julia-level optimization process and caches information for later uses:
> - computes "purity" (i.e. side-effect-freeness) of the optimized frame
> - computes inlining cost and cache the inlineability in `opt.src.inlineable`
> - stores the result of optimization in `caller.src`
> * by default, `caller.src` will be an optimized `CodeInfo` object transformed from `ir`
> * in a case when this frame has been proven pure, `ConstAPI` object wrapping the constant
> value will be kept in `caller.src` instead, so that the runtime system will use
> the constant calling convention
>
> !!! note
>     The lifetimes of `opt` and `ir` end by the end of this process.
>     Still external `AbstractInterpreter` can override this method as necessary to cache them.
>     Note that `transform_result_for_cache` should be overloaded also in such cases,
>     otherwise the default `transform_result_for_cache` implmentation will discard any information
>     other than `CodeInfo`, `Vector{UInt8}` or `ConstAPI`.

This commit also adds a new overload `infresult_iterator` so that external
interpreters can tweak the behavior of post processings of `_typeinf`.
Especially, this change is motivated by the need for JET, whose post-optimization
processing needs references of `InferenceState`.

base/compiler/optimize.jl

@@ -54,10 +54,9 @@ end
 
 include("compiler/ssair/driver.jl")
 
-mutable struct OptimizationState
+struct OptimizationState
     linfo::MethodInstance
     src::CodeInfo
-    ir::Union{Nothing, IRCode}
     stmt_info::Vector{Any}
     mod::Module
     sptypes::Vector{Any} # static parameters
@@ -69,8 +68,7 @@ mutable struct OptimizationState
             EdgeTracker(s_edges, frame.valid_worlds),
             WorldView(code_cache(interp), frame.world),
             interp)
-        return new(frame.linfo,
-                   frame.src, nothing, frame.stmt_info, frame.mod,
+        return new(frame.linfo, frame.src, frame.stmt_info, frame.mod,
                    frame.sptypes, frame.slottypes, inlining)
     end
     function OptimizationState(linfo::MethodInstance, src::CodeInfo, params::OptimizationParams, interp::AbstractInterpreter)
@@ -97,8 +95,7 @@ mutable struct OptimizationState
             nothing,
             WorldView(code_cache(interp), get_world_counter()),
             interp)
-        return new(linfo,
-                   src, nothing, stmt_info, mod,
+        return new(linfo, src, stmt_info, mod,
                    sptypes_from_meth_instance(linfo), slottypes, inlining)
     end
 end
@@ -109,11 +106,10 @@ function OptimizationState(linfo::MethodInstance, params::OptimizationParams, in
     return OptimizationState(linfo, src, params, interp)
 end
 
-function ir_to_codeinf!(opt::OptimizationState)
+function ir_to_codeinf!(opt::OptimizationState, ir::IRCode)
     (; linfo, src) = opt
     optdef = linfo.def
-    replace_code_newstyle!(src, opt.ir::IRCode, isa(optdef, Method) ? Int(optdef.nargs) : 0)
-    opt.ir = nothing
+    replace_code_newstyle!(src, ir, isa(optdef, Method) ? Int(optdef.nargs) : 0)
     widen_all_consts!(src)
     src.inferred = true
     # finish updating the result struct
@@ -383,18 +379,27 @@ struct ConstAPI
 end
 
 """
-    finish(interp::AbstractInterpreter, opt::OptimizationState,
-           params::OptimizationParams, ir::IRCode, caller::InferenceResult) -> analyzed::Union{Nothing,ConstAPI}
-
-Post process information derived by Julia-level optimizations for later uses:
-- computes "purity", i.e. side-effect-freeness
-- computes inlining cost
-
-In a case when the purity is proven, `finish` can return `ConstAPI` object wrapping the constant
-value so that the runtime system will use the constant calling convention for the method calls.
+    finish!(interp::AbstractInterpreter,
+        opt::OptimizationState, ir::IRCode, caller::InferenceResult)
+
+Runs post-Julia-level optimization process and caches information for later uses:
+- computes "purity" (i.e. side-effect-freeness) of the optimized frame
+- computes inlining cost and cache the inlineability in `opt.src.inlineable`
+- stores the result of optimization in `caller.src`
+  * by default, `caller.src` will be an optimized `CodeInfo` object transformed from `ir`
+  * in a case when this frame has been proven pure, `ConstAPI` object wrapping the constant
+    value will be kept in `caller.src` instead, so that the runtime system will use
+    the constant calling convention
+
+!!! note
+    The lifetimes of `opt` and `ir` end by the end of this process.
+    Still external `AbstractInterpreter` can override this method as necessary to cache them.
+    Note that `transform_result_for_cache` should be overloaded also in such cases,
+    otherwise the default `transform_result_for_cache` implmentation will discard any information
+    other than `CodeInfo`, `Vector{UInt8}` or `ConstAPI`.
 """
-function finish(interp::AbstractInterpreter, opt::OptimizationState,
-                params::OptimizationParams, ir::IRCode, caller::InferenceResult)
+function finish!(interp::AbstractInterpreter,
+    opt::OptimizationState, ir::IRCode, caller::InferenceResult)
     (; src, linfo) = opt
     (; def, specTypes) = linfo
 
@@ -452,8 +457,6 @@ function finish(interp::AbstractInterpreter, opt::OptimizationState,
         end
     end
 
-    opt.ir = ir
-
     # determine and cache inlineability
     union_penalties = false
     if !force_noinline
@@ -480,6 +483,7 @@ function finish(interp::AbstractInterpreter, opt::OptimizationState,
             # obey @inline declaration if a dispatch barrier would not help
         else
             # compute the cost (size) of inlining this code
+            params = opt.inlining.params
             cost_threshold = default = params.inline_cost_threshold
             if result ⊑ Tuple && !isconcretetype(widenconst(result))
                 cost_threshold += params.inline_tupleret_bonus
@@ -499,14 +503,27 @@ function finish(interp::AbstractInterpreter, opt::OptimizationState,
         end
     end
 
-    return analyzed
+    caller.valid_worlds = (opt.inlining.et::EdgeTracker).valid_worlds[]
+
+    if isa(analyzed, ConstAPI)
+        # XXX: The work in ir_to_codeinf! is essentially wasted. The only reason
+        # we're doing it is so that code_llvm can return the code
+        # for the `return ...::Const` (which never runs anyway). We should do this
+        # as a post processing step instead.
+        ir_to_codeinf!(opt, ir)
+        caller.src = analyzed
+    else
+        caller.src = ir_to_codeinf!(opt, ir)
+    end
+
+    return nothing
 end
 
 # run the optimization work
-function optimize(interp::AbstractInterpreter, opt::OptimizationState,
-                  params::OptimizationParams, caller::InferenceResult)
+function optimize!(interp::AbstractInterpreter,
+    opt::OptimizationState, caller::InferenceResult)
     @timeit "optimizer" ir = run_passes(opt.src, opt)
-    return finish(interp, opt, params, ir, caller)
+    @timeit "finish!"   finish!(interp, opt, ir, caller)
 end
 
 function run_passes(ci::CodeInfo, sv::OptimizationState)

base/compiler/typeinfer.jl

@@ -210,23 +210,20 @@ function typeinf(interp::AbstractInterpreter, frame::InferenceState)
     end
 end
 
-function finish!(interp::AbstractInterpreter, caller::InferenceResult)
-    # If we didn't transform the src for caching, we may have to transform
-    # it anyway for users like typeinf_ext. Do that here.
-    opt = caller.src
-    if opt isa OptimizationState # implies `may_optimize(interp) === true`
-        if opt.ir !== nothing
-            caller.src = ir_to_codeinf!(opt)
-        end
-    end
-    return caller.src
-end
-
 function _typeinf(interp::AbstractInterpreter, frame::InferenceState)
     typeinf_nocycle(interp, frame) || return false # frame is now part of a higher cycle
     # with no active ip's, frame is done
     frames = frame.callers_in_cycle
     isempty(frames) && push!(frames, frame)
+    finish_infstates!(interp, frames)
+    # collect results for the new expanded frame
+    results = infresult_iterator(interp, frames)
+    optimize!(interp, results)
+    cache_results!(interp, results)
+    return true
+end
+
+function finish_infstates!(interp::AbstractInterpreter, frames::Vector{InferenceState})
     valid_worlds = WorldRange()
     for caller in frames
         @assert !(caller.dont_work_on_me)
@@ -240,29 +237,35 @@ function _typeinf(interp::AbstractInterpreter, frame::InferenceState)
         # finalize and record the linfo result
         caller.inferred = true
     end
-    # collect results for the new expanded frame
-    results = Tuple{InferenceResult, Vector{Any}, Bool}[
-            ( frames[i].result,
-              frames[i].stmt_edges[1]::Vector{Any},
-              frames[i].cached )
-        for i in 1:length(frames) ]
-    empty!(frames)
-    for (caller, _, _) in results
+end
+
+struct InfResultInfo
+    caller::InferenceResult
+    edges::Vector{Any}
+    cached::Bool
+end
+
+# returns iterator on which `optimize!` and `postopt_process!` work on
+function infresult_iterator(_::AbstractInterpreter, frames::Vector{InferenceState})
+    results = InfResultInfo[ InfResultInfo(
+        frames[i].result,
+        frames[i].stmt_edges[1]::Vector{Any},
+        frames[i].cached ) for i in 1:length(frames) ]
+    empty!(frames) # discard `InferenceState` now
+    return results
+end
+
+function optimize!(interp::AbstractInterpreter, results::Vector{InfResultInfo})
+    for (; caller) in results
         opt = caller.src
         if opt isa OptimizationState # implies `may_optimize(interp) === true`
-            analyzed = optimize(interp, opt, OptimizationParams(interp), caller)
-            if isa(analyzed, ConstAPI)
-                # XXX: The work in ir_to_codeinf! is essentially wasted. The only reason
-                # we're doing it is so that code_llvm can return the code
-                # for the `return ...::Const` (which never runs anyway). We should do this
-                # as a post processing step instead.
-                ir_to_codeinf!(opt)
-                caller.src = analyzed
-            end
-            caller.valid_worlds = (opt.inlining.et::EdgeTracker).valid_worlds[]
+            optimize!(interp, opt, caller)
         end
     end
-    for (caller, edges, cached) in results
+end
+
+function cache_results!(interp::AbstractInterpreter, results::Vector{InfResultInfo})
+    for (; caller, edges, cached) in results
         valid_worlds = caller.valid_worlds
         if last(valid_worlds) >= get_world_counter()
             # if we aren't cached, we don't need this edge
@@ -272,9 +275,7 @@ function _typeinf(interp::AbstractInterpreter, frame::InferenceState)
         if cached
             cache_result!(interp, caller)
         end
-        finish!(interp, caller)
     end
-    return true
 end
 
 function CodeInstance(result::InferenceResult, @nospecialize(inferred_result),
@@ -349,11 +350,6 @@ end
 
 function transform_result_for_cache(interp::AbstractInterpreter, linfo::MethodInstance,
                                     valid_worlds::WorldRange, @nospecialize(inferred_result))
-    # If we decided not to optimize, drop the OptimizationState now.
-    # External interpreters can override as necessary to cache additional information
-    if inferred_result isa OptimizationState
-        inferred_result = ir_to_codeinf!(inferred_result)
-    end
     if inferred_result isa CodeInfo
         inferred_result.min_world = first(valid_worlds)
         inferred_result.max_world = last(valid_worlds)