concrete-eval: Use concrete eval information even if the result is to…

…o large (#47283)

When we originally implemented concrete-eval, we decided not to create `Const`
lattice elements for constants that are too large, on the fear that these
would end up in the IR and blowing up the size. Now that we have some
experience with this, I think that decision was incorrect for several reasons:

1. We've already performed the concrete evaluation (and allocated the big
   object), so we're just throwing away precision here that we could
   have otherwise used (Although if the call result is unused, we probably
   shouldn't do concrete eval at all - see #46774).
2. There's a number of other places in the compiler where we read large
   values into `Const`. Unless we add these kinds of check there too,
   we need to have appropriate guards in the optimizer and the cache
   anyway, to prevent the IR size blowup.
3. It turns out that throwing away this precision actually causes
   significant performance problems for code that is just over the line.
   Consider for example a lookup of a small struct inside a large,
   multi-level constant structure. The final result might be quite
   tiny, but if we refuse to propagate the intermediate levels,
   we might end up doing an (expensive) full-constprop when propagating
   the constant information could have given us a much cheaper
   concrete evaluation.

This commit simply removes that check. If we see any regressions
as a result of this, we should see if there are additional guards
needed in the optimizer.

base/compiler/abstractinterpretation.jl

@@ -841,13 +841,7 @@ function concrete_eval_call(interp::AbstractInterpreter,
             # The evaluation threw. By :consistent-cy, we're guaranteed this would have happened at runtime
             return ConstCallResults(Union{}, ConcreteResult(edge, result.effects), result.effects, edge)
         end
-        if is_inlineable_constant(value) || call_result_unused(si)
-            # If the constant is not inlineable, still do the const-prop, since the
-            # code that led to the creation of the Const may be inlineable in the same
-            # circumstance and may be optimizable.
-            return ConstCallResults(Const(value), ConcreteResult(edge, EFFECTS_TOTAL, value), EFFECTS_TOTAL, edge)
-        end
-        return false
+        return ConstCallResults(Const(value), ConcreteResult(edge, EFFECTS_TOTAL, value), EFFECTS_TOTAL, edge)
     else # eligible for semi-concrete evaluation
         return true
     end

base/compiler/ssair/inlining.jl

@@ -1169,7 +1169,7 @@ function handle_invoke_call!(todo::Vector{Pair{Int,Any}},
     end
     result = info.result
     invokesig = sig.argtypes
-    if isa(result, ConcreteResult)
+    if isa(result, ConcreteResult) && may_inline_concrete_result(result)
         item = concrete_result_item(result, state; invokesig)
     else
         argtypes = invoke_rewrite(sig.argtypes)
@@ -1296,7 +1296,11 @@ function handle_any_const_result!(cases::Vector{InliningCase},
     @nospecialize(info::CallInfo), flag::UInt8, state::InliningState;
     allow_abstract::Bool, allow_typevars::Bool)
     if isa(result, ConcreteResult)
-        return handle_concrete_result!(cases, result, state)
+        if may_inline_concrete_result(result)
+            return handle_concrete_result!(cases, result, state)
+        else
+            result = nothing
+        end
     end
     if isa(result, SemiConcreteResult)
         result = inlining_policy(state.interp, result, info, flag, result.mi, argtypes)
@@ -1483,15 +1487,12 @@ function handle_concrete_result!(cases::Vector{InliningCase}, result::ConcreteRe
     return true
 end
 
+may_inline_concrete_result(result::ConcreteResult) =
+    isdefined(result, :result) && is_inlineable_constant(result.result)
+
 function concrete_result_item(result::ConcreteResult, state::InliningState;
     invokesig::Union{Nothing,Vector{Any}}=nothing)
-    if !isdefined(result, :result) || !is_inlineable_constant(result.result)
-        et = InliningEdgeTracker(state.et, invokesig)
-        case = compileable_specialization(result.mi, result.effects, et;
-            compilesig_invokes=state.params.compilesig_invokes)
-        @assert case !== nothing "concrete evaluation should never happen for uncompileable callsite"
-        return case
-    end
+    @assert may_inline_concrete_result(result)
     @assert result.effects === EFFECTS_TOTAL
     return ConstantCase(quoted(result.result))
 end
@@ -1524,7 +1525,7 @@ function handle_opaque_closure_call!(todo::Vector{Pair{Int,Any}},
         mi = result.result.linfo
         validate_sparams(mi.sparam_vals) || return nothing
         item = resolve_todo(mi, result.result, sig.argtypes, info, flag, state)
-    elseif isa(result, ConcreteResult)
+    elseif isa(result, ConcreteResult) && may_inline_concrete_result(result)
         item = concrete_result_item(result, state)
     else
         item = analyze_method!(info.match, sig.argtypes, info, flag, state; allow_typevars=false)