Allow irinterp to refine nothrow effect

This addresses a remaining todo in the irinterp code to allow it
to compute whether its particular evaluation refined `nothrow`.
As a result, we can re-enable it for a larger class of ir (we had
previously disabled it to avoid regressing cases where regular
constprop was able to prove a `nothrow` refinement, but irinterp
was not).

Author: Keno

base/compiler/abstractinterpretation.jl

@@ -830,9 +830,7 @@ function concrete_eval_eligible(interp::AbstractInterpreter,
         if is_all_const_arg(arginfo, #=start=#2)
             return true
         else
-            # TODO: `is_nothrow` is not an actual requirement here, this is just a hack
-            # to avoid entering semi concrete eval while it doesn't properly override effects
-            return is_nothrow(result.effects) ? false : nothing
+            return false
         end
     end
     return nothing
@@ -1004,10 +1002,11 @@ function abstract_call_method_with_const_args(interp::AbstractInterpreter,
             ir = codeinst_to_ir(interp, code)
             if isa(ir, IRCode)
                 irsv = IRInterpretationState(interp, ir, mi, sv.world, arginfo.argtypes)
-                rt = ir_abstract_constant_propagation(interp, irsv)
+                rt, nothrow = ir_abstract_constant_propagation(interp, irsv)
                 @assert !(rt isa Conditional || rt isa MustAlias) "invalid lattice element returned from IR interpretation"
                 if !isa(rt, Type) || typeintersect(rt, Bool) === Union{}
-                    return ConstCallResults(rt, SemiConcreteResult(mi, ir, result.effects), result.effects, mi)
+                    new_effects = Effects(result.effects; nothrow=nothrow)
+                    return ConstCallResults(rt, SemiConcreteResult(mi, ir, new_effects), new_effects, mi)
                 end
             end
         end

base/compiler/optimize.jl

@@ -649,7 +649,7 @@ function convert_to_ircode(ci::CodeInfo, sv::OptimizationState)
                 insert!(codelocs, idx + 1, codelocs[idx])
                 insert!(ssavaluetypes, idx + 1, Union{})
                 insert!(stmtinfo, idx + 1, NoCallInfo())
-                insert!(ssaflags, idx + 1, ssaflags[idx])
+                insert!(ssaflags, idx + 1, IR_FLAG_NOTHROW)
                 if ssachangemap === nothing
                     ssachangemap = fill(0, nstmts)
                 end

base/compiler/ssair/irinterp.jl

@@ -144,20 +144,20 @@ function concrete_eval_invoke(interp::AbstractInterpreter,
     inst::Expr, mi::MethodInstance, irsv::IRInterpretationState)
     mi_cache = WorldView(code_cache(interp), irsv.world)
     code = get(mi_cache, mi, nothing)
-    code === nothing && return nothing
+    code === nothing && return Pair{Any, Bool}(nothing, false)
     argtypes = collect_argtypes(interp, inst.args[2:end], nothing, irsv.ir)
-    argtypes === nothing && return Union{}
+    argtypes === nothing && return Pair{Any, Bool}(Union{}, false)
     effects = decode_effects(code.ipo_purity_bits)
     if is_foldable(effects) && is_all_const_arg(argtypes, #=start=#1)
         args = collect_const_args(argtypes, #=start=#1)
         world = get_world_counter(interp)
         value = try
             Core._call_in_world_total(world, args...)
         catch
-            return Union{}
+            return Pair{Any, Bool}(Union{}, false)
         end
         if is_inlineable_constant(value)
-            return Const(value)
+            return Pair{Any, Bool}(Const(value), true)
         end
     else
         ir′ = codeinst_to_ir(interp, code)
@@ -166,7 +166,7 @@ function concrete_eval_invoke(interp::AbstractInterpreter,
             return _ir_abstract_constant_propagation(interp, irsv′)
         end
     end
-    return nothing
+    return Pair{Any, Bool}(nothing, is_nothrow(effects))
 end
 
 function abstract_eval_phi_stmt(interp::AbstractInterpreter, phi::PhiNode, ::Int, irsv::IRInterpretationState)
@@ -225,16 +225,21 @@ function reprocess_instruction!(interp::AbstractInterpreter,
             (; rt, effects) = abstract_eval_statement_expr(interp, inst, nothing, ir, irsv.mi)
             # All other effects already guaranteed effect free by construction
             if is_nothrow(effects)
+                ir.stmts[idx][:flag] |= IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW
                 if isa(rt, Const) && is_inlineable_constant(rt.val)
                     ir.stmts[idx][:inst] = quoted(rt.val)
-                else
-                    ir.stmts[idx][:flag] |= IR_FLAG_EFFECT_FREE
                 end
             end
         elseif head === :invoke
             mi′ = inst.args[1]::MethodInstance
             if mi′ !== irsv.mi # prevent infinite loop
-                rt = concrete_eval_invoke(interp, inst, mi′, irsv)
+                rt, nothrow = concrete_eval_invoke(interp, inst, mi′, irsv)
+                if nothrow
+                    ir.stmts[idx][:flag] |= IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW
+                    if isa(rt, Const) && is_inlineable_constant(rt.val)
+                        ir.stmts[idx][:inst] = quoted(rt.val)
+                    end
+                end
             end
         elseif head === :throw_undef_if_not || # TODO: Terminate interpretation early if known false?
                head === :gc_preserve_begin ||
@@ -416,7 +421,15 @@ function _ir_abstract_constant_propagation(interp::AbstractInterpreter, irsv::IR
         end
     end
 
-    return maybe_singleton_const(ultimate_rt)
+    nothrow = true
+    for i = 1:length(ir.stmts)
+        if (ir.stmts[i][:flag] & IR_FLAG_NOTHROW) == 0
+            nothrow = false
+            break
+        end
+    end
+
+    return Pair{Any, Bool}(maybe_singleton_const(ultimate_rt), nothrow)
 end
 
 function ir_abstract_constant_propagation(interp::AbstractInterpreter, irsv::IRInterpretationState)

base/compiler/ssair/slot2ssa.jl

@@ -203,7 +203,7 @@ function strip_trailing_junk!(ci::CodeInfo, code::Vector{Any}, info::Vector{Call
         push!(ssavaluetypes, Union{})
         push!(codelocs, 0)
         push!(info, NoCallInfo())
-        push!(ssaflags, IR_FLAG_NULL)
+        push!(ssaflags, IR_FLAG_NOTHROW)
     end
     nothing
 end