inference: Remove special casing for !

We have a handful of cases in inference where we look up functions by name
(using `istopfunction`) and give them special behavior. I'd like to remove
these. They're not only aesthetically ugly, but because they depend on binding
lookups, rather than values, they have unclear semantics as those bindings
change. They are also unsound should a user use the same name for something
different in their own top modules (of course, it's unlikely that a user would
do such a thing, but it's bad that they can't).

This particular PR removes the special case for `!`, which was there to
strengthen the inference result for `!` on Conditional. However, with
a little bit of strengthening of the rest of the system, this can be
equally well evaluated through the existing InterConditional mechanism.

Author: Keno

base/compiler/abstractinterpretation.jl

@@ -13,6 +13,31 @@ call_result_unused(sv::InferenceState, currpc::Int) =
     isexpr(sv.src.code[currpc], :call) && isempty(sv.ssavalue_uses[currpc])
 call_result_unused(si::StmtInfo) = !si.used
 
+is_const_bool_or_bottom(@nospecialize(b)) = (isa(b, Const) && isa(b.val, Bool)) || b == Bottom
+function can_propagate_conditional(@nospecialize(rt), argtypes::Vector{Any})
+    isa(rt, InterConditional) || return false
+    if rt.slot > length(argtypes)
+        # In the vararg tail - can't be conditional
+        @assert isvarargtype(argtypes[end])
+        return false
+    end
+    return isa(argtypes[rt.slot], Conditional) &&
+        is_const_bool_or_bottom(rt.thentype) && is_const_bool_or_bottom(rt.thentype)
+end
+
+function propagate_conditional(rt::InterConditional, cond::Conditional)
+    new_thentype = rt.thentype === Const(false) ? cond.elsetype : cond.thentype
+    new_elsetype = rt.elsetype === Const(true) ? cond.thentype : cond.elsetype
+    if rt.thentype == Bottom
+        @assert rt.elsetype != Bottom
+        return Conditional(cond.slot, Bottom, new_elsetype)
+    elseif rt.elsetype == Bottom
+        @assert rt.thentype != Bottom
+        return Conditional(cond.slot, new_thentype, Bottom)
+    end
+    return Conditional(cond.slot, new_thentype, new_elsetype)
+end
+
 function abstract_call_gf_by_type(interp::AbstractInterpreter, @nospecialize(f),
                                   arginfo::ArgInfo, si::StmtInfo, @nospecialize(atype),
                                   sv::AbsIntState, max_methods::Int)
@@ -156,6 +181,15 @@ function abstract_call_gf_by_type(interp::AbstractInterpreter, @nospecialize(f),
         end
         @assert !(this_conditional isa Conditional || this_rt isa MustAlias) "invalid lattice element returned from inter-procedural context"
         seen += 1
+
+        if can_propagate_conditional(this_conditional, argtypes)
+            # The only case where we need to keep this in rt is where
+            # we can directly propagate the conditional to a slot argument
+            # that is not one of our arguments, otherwise we keep all the
+            # relevant information in `conditionals` below.
+            this_rt = this_conditional
+        end
+
         rettype = rettype ⊔ₚ this_rt
         exctype = exctype ⊔ₚ this_exct
         if has_conditional(𝕃ₚ, sv) && this_conditional !== Bottom && is_lattice_bool(𝕃ₚ, rettype) && fargs !== nothing
@@ -409,6 +443,9 @@ function from_interconditional(𝕃ᵢ::AbstractLattice, @nospecialize(rt), sv::
     has_conditional(𝕃ᵢ, sv) || return widenconditional(rt)
     (; fargs, argtypes) = arginfo
     fargs === nothing && return widenconditional(rt)
+    if can_propagate_conditional(rt, argtypes)
+        return propagate_conditional(rt, argtypes[rt.slot]::Conditional)
+    end
     slot = 0
     alias = nothing
     thentype = elsetype = Any
@@ -2217,13 +2254,6 @@ function abstract_call_known(interp::AbstractInterpreter, @nospecialize(f),
         end
     elseif is_return_type(f)
         return return_type_tfunc(interp, argtypes, si, sv)
-    elseif la == 2 && istopfunction(f, :!)
-        # handle Conditional propagation through !Bool
-        aty = argtypes[2]
-        if isa(aty, Conditional)
-            call = abstract_call_gf_by_type(interp, f, ArgInfo(fargs, Any[Const(f), Bool]), si, Tuple{typeof(f), Bool}, sv, max_methods) # make sure we've inferred `!(::Bool)`
-            return CallMeta(Conditional(aty.slot, aty.elsetype, aty.thentype), Any, call.effects, call.info)
-        end
     elseif la == 3 && istopfunction(f, :!==)
         # mark !== as exactly a negated call to ===
         call = abstract_call_gf_by_type(interp, f, ArgInfo(fargs, Any[Const(f), Any, Any]), si, Tuple{typeof(f), Any, Any}, sv, max_methods)
@@ -3194,7 +3224,7 @@ function update_bestguess!(interp::AbstractInterpreter, frame::InferenceState,
     # narrow representation of bestguess slightly to prepare for tmerge with rt
     if rt isa InterConditional && bestguess isa Const
         slot_id = rt.slot
-        old_id_type = slottypes[slot_id]
+        old_id_type = widenconditional(slottypes[slot_id])
         if bestguess.val === true && rt.elsetype !== Bottom
             bestguess = InterConditional(slot_id, old_id_type, Bottom)
         elseif bestguess.val === false && rt.thentype !== Bottom

base/compiler/inferencestate.jl

@@ -312,6 +312,9 @@ mutable struct InferenceState
         nargtypes = length(argtypes)
         for i = 1:nslots
             argtyp = (i > nargtypes) ? Bottom : argtypes[i]
+            if argtyp === Bool && has_conditional(typeinf_lattice(interp))
+                argtyp = Conditional(i, Const(true), Const(false))
+            end
             slottypes[i] = argtyp
             bb_vartable1[i] = VarState(argtyp, i > nargtypes)
         end

base/compiler/tfuncs.jl

@@ -227,10 +227,19 @@ end
 @nospecs shift_tfunc(𝕃::AbstractLattice, x, y) = shift_tfunc(widenlattice(𝕃), x, y)
 @nospecs shift_tfunc(::JLTypeLattice, x, y) = widenconst(x)
 
+function not_tfunc(𝕃::AbstractLattice, @nospecialize(b))
+    if isa(b, Conditional)
+        return Conditional(b.slot, b.elsetype, b.thentype)
+    elseif isa(b, Const)
+        return Const(not_int(b.val))
+    end
+    return math_tfunc(𝕃, b)
+end
+
 add_tfunc(and_int, 2, 2, and_int_tfunc, 1)
 add_tfunc(or_int, 2, 2, or_int_tfunc, 1)
 add_tfunc(xor_int, 2, 2, math_tfunc, 1)
-add_tfunc(not_int, 1, 1, math_tfunc, 0) # usually used as not_int(::Bool) to negate a condition
+add_tfunc(not_int, 1, 1, not_tfunc, 0) # usually used as not_int(::Bool) to negate a condition
 add_tfunc(shl_int, 2, 2, shift_tfunc, 1)
 add_tfunc(lshr_int, 2, 2, shift_tfunc, 1)
 add_tfunc(ashr_int, 2, 2, shift_tfunc, 1)

test/compiler/inference.jl

@@ -5866,3 +5866,8 @@ end
 bar54341(args...) = foo54341(4, args...)
 
 @test Core.Compiler.return_type(bar54341, Tuple{Vararg{Int}}) === Int
+
+# InterConditional rt with Vararg argtypes
+fcondvarargs(a, b, c, d) = isa(d, Int64)
+gcondvarargs(a, x...) = return fcondvarargs(a, x...) ? isa(a, Int64) : !isa(a, Int64)
+@test Core.Compiler.return_type(gcondvarargs, Tuple{Vararg{Any}}) === Bool