Hook up IR_FLAG_NOTHROW (#45752)

Keno · web-flow · commit a2cc0f4f9bf0 · 2022-06-22T16:08:00.000-04:00
I added the flag in #45272, but didn't hook it up to the nothrow model. In the fullness of time, these should forwarded from inference and only recomputed if necessary, but for the moment, just make it work.
diff --git a/base/compiler/optimize.jl b/base/compiler/optimize.jl
@@ -188,81 +188,90 @@ function stmt_affects_purity(@nospecialize(stmt), ir)
 end
 
 """
-    stmt_effect_free(stmt, rt, src::Union{IRCode,IncrementalCompact})
+    stmt_effect_flags(stmt, rt, src::Union{IRCode,IncrementalCompact})
 
-Determine whether a `stmt` is "side-effect-free", i.e. may be removed if it has no uses.
+Returns a tuple of (effect_free_and_nothrow, nothrow) for a given statement.
 """
-function stmt_effect_free(@nospecialize(stmt), @nospecialize(rt), src::Union{IRCode,IncrementalCompact})
-    isa(stmt, PiNode) && return true
-    isa(stmt, PhiNode) && return true
-    isa(stmt, ReturnNode) && return false
-    isa(stmt, GotoNode) && return false
-    isa(stmt, GotoIfNot) && return false
-    isa(stmt, Slot) && return false # Slots shouldn't occur in the IR at this point, but let's be defensive here
-    isa(stmt, GlobalRef) && return isdefined(stmt.mod, stmt.name)
+function stmt_effect_flags(@nospecialize(stmt), @nospecialize(rt), src::Union{IRCode,IncrementalCompact})
+    # TODO: We're duplicating analysis from inference here.
+    isa(stmt, PiNode) && return (true, true)
+    isa(stmt, PhiNode) && return (true, true)
+    isa(stmt, ReturnNode) && return (false, true)
+    isa(stmt, GotoNode) && return (false, true)
+    isa(stmt, GotoIfNot) && return (false, argextype(stmt.cond, src) ⊑ Bool)
+    isa(stmt, Slot) && return (false, false) # Slots shouldn't occur in the IR at this point, but let's be defensive here
+    if isa(stmt, GlobalRef)
+        nothrow = isdefined(stmt.mod, stmt.name)
+        return (nothrow, nothrow)
+    end
     if isa(stmt, Expr)
         (; head, args) = stmt
         if head === :static_parameter
             etyp = (isa(src, IRCode) ? src.sptypes : src.ir.sptypes)[args[1]::Int]
             # if we aren't certain enough about the type, it might be an UndefVarError at runtime
-            return isa(etyp, Const)
+            nothrow = isa(etyp, Const)
+            return (nothrow, nothrow)
         end
         if head === :call
             f = argextype(args[1], src)
             f = singleton_type(f)
-            f === nothing && return false
+            f === nothing && return (false, false)
             if isa(f, IntrinsicFunction)
-                intrinsic_effect_free_if_nothrow(f) || return false
-                return intrinsic_nothrow(f,
-                        Any[argextype(args[i], src) for i = 2:length(args)])
+                nothrow = intrinsic_nothrow(f,
+                    Any[argextype(args[i], src) for i = 2:length(args)])
+                nothrow || return (false, false)
+                return (intrinsic_effect_free_if_nothrow(f), nothrow)
             end
-            contains_is(_PURE_BUILTINS, f) && return true
+            contains_is(_PURE_BUILTINS, f) && return (true, true)
             # `get_binding_type` sets the type to Any if the binding doesn't exist yet
             if f === Core.get_binding_type
                 length(args) == 3 || return false
                 M, s = argextype(args[2], src), argextype(args[3], src)
-                return get_binding_type_effect_free(M, s)
+                total = get_binding_type_effect_free(M, s)
+                return (total, total)
             end
-            contains_is(_EFFECT_FREE_BUILTINS, f) || return false
-            rt === Bottom && return false
-            return _builtin_nothrow(f, Any[argextype(args[i], src) for i = 2:length(args)], rt)
+            rt === Bottom && return (false, false)
+            nothrow = _builtin_nothrow(f, Any[argextype(args[i], src) for i = 2:length(args)], rt)
+            nothrow || return (false, false)
+            return (contains_is(_EFFECT_FREE_BUILTINS, f), nothrow)
         elseif head === :new
             typ = argextype(args[1], src)
             # `Expr(:new)` of unknown type could raise arbitrary TypeError.
             typ, isexact = instanceof_tfunc(typ)
-            isexact || return false
-            isconcretedispatch(typ) || return false
+            isexact || return (false, false)
+            isconcretedispatch(typ) || return (false, false)
             typ = typ::DataType
-            fieldcount(typ) >= length(args) - 1 || return false
+            fieldcount(typ) >= length(args) - 1 || return (false, false)
             for fld_idx in 1:(length(args) - 1)
                 eT = argextype(args[fld_idx + 1], src)
                 fT = fieldtype(typ, fld_idx)
-                eT ⊑ fT || return false
+                eT ⊑ fT || return (false, false)
             end
-            return true
+            return (true, true)
         elseif head === :foreigncall
-            return foreigncall_effect_free(stmt, src)
+            total = foreigncall_effect_free(stmt, src)
+            return (total, total)
         elseif head === :new_opaque_closure
-            length(args) < 4 && return false
+            length(args) < 4 && return (false, false)
             typ = argextype(args[1], src)
             typ, isexact = instanceof_tfunc(typ)
-            isexact || return false
-            typ ⊑ Tuple || return false
+            isexact || return (false, false)
+            typ ⊑ Tuple || return (false, false)
             rt_lb = argextype(args[2], src)
             rt_ub = argextype(args[3], src)
             src = argextype(args[4], src)
             if !(rt_lb ⊑ Type && rt_ub ⊑ Type && src ⊑ Method)
-                return false
+                return (false, false)
             end
-            return true
+            return (true, true)
         elseif head === :isdefined || head === :the_exception || head === :copyast || head === :inbounds || head === :boundscheck
-            return true
+            return (true, true)
         else
             # e.g. :loopinfo
-            return false
+            return (false, false)
         end
     end
-    return true
+    return (true, true)
 end
 
 function foreigncall_effect_free(stmt::Expr, src::Union{IRCode,IncrementalCompact})
@@ -421,7 +430,7 @@ function finish(interp::AbstractInterpreter, opt::OptimizationState,
             for i in 1:length(ir.stmts)
                 node = ir.stmts[i]
                 stmt = node[:inst]
-                if stmt_affects_purity(stmt, ir) && !stmt_effect_free(stmt, node[:type], ir)
+                if stmt_affects_purity(stmt, ir) && !stmt_effect_flags(stmt, node[:type], ir)[1]
                     proven_pure = false
                     break
                 end
diff --git a/base/compiler/ssair/EscapeAnalysis/EscapeAnalysis.jl b/base/compiler/ssair/EscapeAnalysis/EscapeAnalysis.jl
@@ -31,7 +31,7 @@ import Core.Compiler: # Core.Compiler specific definitions
     isbitstype, isexpr, is_meta_expr_head, println, widenconst, argextype, singleton_type,
     fieldcount_noerror, try_compute_field, try_compute_fieldidx, hasintersect, ⊑,
     intrinsic_nothrow, array_builtin_common_typecheck, arrayset_typecheck,
-    setfield!_nothrow, alloc_array_ndims, stmt_effect_free, check_effect_free!
+    setfield!_nothrow, alloc_array_ndims, check_effect_free!
 
 include(x) = _TOP_MOD.include(@__MODULE__, x)
 if _TOP_MOD === Core.Compiler
@@ -1333,7 +1333,7 @@ function escape_call!(astate::AnalysisState, pc::Int, args::Vector{Any})
         return # ThrownEscape is already checked
     else
         # we escape statements with the `ThrownEscape` property using the effect-freeness
-        # computed by `stmt_effect_free` invoked within inlining
+        # computed by `stmt_effect_flags` invoked within inlining
         # TODO throwness ≠ "effect-free-ness"
         if is_effect_free(astate.ir, pc)
             add_liveness_changes!(astate, pc, args, 2)
diff --git a/base/compiler/ssair/inlining.jl b/base/compiler/ssair/inlining.jl
@@ -935,7 +935,9 @@ function handle_single_case!(
         stmt.head = :invoke
         pushfirst!(stmt.args, case.invoke)
         if is_removable_if_unused(case.effects)
-            ir[SSAValue(idx)][:flag] |= IR_FLAG_EFFECT_FREE
+            ir[SSAValue(idx)][:flag] |= IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW
+        elseif is_nothrow(case.effects)
+            ir[SSAValue(idx)][:flag] |= IR_FLAG_NOTHROW
         end
     elseif case === nothing
         # Do, well, nothing
@@ -1138,11 +1140,13 @@ end
 # For primitives, we do that right here. For proper calls, we will
 # discover this when we consult the caches.
 function check_effect_free!(ir::IRCode, idx::Int, @nospecialize(stmt), @nospecialize(rt))
-    if stmt_effect_free(stmt, rt, ir)
-        ir.stmts[idx][:flag] |= IR_FLAG_EFFECT_FREE
-        return true
+    (total, nothrow) = stmt_effect_flags(stmt, rt, ir)
+    if total
+        ir.stmts[idx][:flag] |= IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW
+    elseif nothrow
+        ir.stmts[idx][:flag] |= IR_FLAG_NOTHROW
     end
-    return false
+    return total
 end
 
 # Handles all analysis and inlining of intrinsics and builtins. In particular,
diff --git a/base/compiler/ssair/ir.jl b/base/compiler/ssair/ir.jl
@@ -250,7 +250,7 @@ function setindex!(is::InstructionStream, newval::Instruction, idx::Int)
     is.flag[idx] = newval[:flag]
     return is
 end
-function setindex!(is::InstructionStream, newval::AnySSAValue, idx::Int)
+function setindex!(is::InstructionStream, newval::Union{AnySSAValue, Nothing}, idx::Int)
     is.inst[idx] = newval
     return is
 end
@@ -343,7 +343,7 @@ function getindex(x::IRCode, s::SSAValue)
     end
 end
 
-function setindex!(x::IRCode, repl::Union{Instruction, AnySSAValue}, s::SSAValue)
+function setindex!(x::IRCode, repl::Union{Instruction, Nothing, AnySSAValue}, s::SSAValue)
     if s.id <= length(x.stmts)
         x.stmts[s.id] = repl
     else
@@ -509,8 +509,11 @@ function insert_node!(ir::IRCode, pos::Int, inst::NewInstruction, attach_after::
     node[:line] = something(inst.line, ir.stmts[pos][:line])
     flag = inst.flag
     if !inst.effect_free_computed
-        if stmt_effect_free(inst.stmt, inst.type, ir)
-            flag |= IR_FLAG_EFFECT_FREE
+        (effect_free_and_nothrow, nothrow) = stmt_effect_flags(inst.stmt, inst.type, ir)
+        if effect_free_and_nothrow
+            flag |= IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW
+        elseif nothrow
+            flag |= IR_FLAG_NOTHROW
         end
     end
     node[:inst], node[:type], node[:flag] = inst.stmt, inst.type, flag
@@ -830,8 +833,13 @@ function insert_node_here!(compact::IncrementalCompact, inst::NewInstruction, re
         resize!(compact, result_idx)
     end
     flag = inst.flag
-    if !inst.effect_free_computed && stmt_effect_free(inst.stmt, inst.type, compact)
-        flag |= IR_FLAG_EFFECT_FREE
+    if !inst.effect_free_computed
+        (effect_free_and_nothrow, nothrow) = stmt_effect_flags(inst.stmt, inst.type, compact)
+        if effect_free_and_nothrow
+            flag |= IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW
+        elseif nothrow
+            flag |= IR_FLAG_NOTHROW
+        end
     end
     node = compact.result[result_idx]
     node[:inst], node[:type], node[:line], node[:flag] = inst.stmt, inst.type, inst.line, flag
diff --git a/base/compiler/tfuncs.jl b/base/compiler/tfuncs.jl
@@ -1758,6 +1758,10 @@ function _builtin_nothrow(@nospecialize(f), argtypes::Array{Any,1}, @nospecializ
         return argtypes[1] ⊑ Module && argtypes[2] ⊑ Symbol
     elseif f === donotdelete
         return true
+    elseif f === Core.finalizer
+        2 <= length(argtypes) <= 4 || return false
+        # Core.finalizer does no error checking - that's done in Base.finalizer
+        return true
     end
     return false
 end
