inference: don't allocate TryCatchFrame for compute_trycatch(::IRCode) (#56835)

`TryCatchFrame` is only required for the abstract interpretation and is
not necessary in `compute_trycatch` within slot2ssa.jl.

@nanosoldier `runbenchmarks("inference", vs=":master")`

Author: aviatesk

Compiler/src/inferencestate.jl

@@ -219,16 +219,29 @@ const CACHE_MODE_GLOBAL   = 0x01 << 0 # cached globally, optimization required
 const CACHE_MODE_LOCAL    = 0x01 << 1 # cached locally, optimization required
 const CACHE_MODE_VOLATILE = 0x01 << 2 # not cached, optimization required
 
-mutable struct TryCatchFrame
+abstract type Handler end
+get_enter_idx(handler::Handler) = get_enter_idx_impl(handler)::Int
+
+mutable struct TryCatchFrame <: Handler
     exct
     scopet
     const enter_idx::Int
     scope_uses::Vector{Int}
-    TryCatchFrame(@nospecialize(exct), @nospecialize(scopet), enter_idx::Int) = new(exct, scopet, enter_idx)
+    TryCatchFrame(@nospecialize(exct), @nospecialize(scopet), enter_idx::Int) =
+        new(exct, scopet, enter_idx)
+end
+TryCatchFrame(stmt::EnterNode, pc::Int) =
+    TryCatchFrame(Bottom, isdefined(stmt, :scope) ? Bottom : nothing, pc)
+get_enter_idx_impl((; enter_idx)::TryCatchFrame) = enter_idx
+
+struct SimpleHandler <: Handler
+    enter_idx::Int
 end
+SimpleHandler(::EnterNode, pc::Int) = SimpleHandler(pc)
+get_enter_idx_impl((; enter_idx)::SimpleHandler) = enter_idx
 
-struct HandlerInfo
-    handlers::Vector{TryCatchFrame}
+struct HandlerInfo{T<:Handler}
+    handlers::Vector{T}
     handler_at::Vector{Tuple{Int,Int}} # tuple of current (handler, exception stack) value at the pc
 end
 
@@ -261,7 +274,7 @@ mutable struct InferenceState
     currbb::Int
     currpc::Int
     ip::BitSet#=TODO BoundedMinPrioritySet=# # current active instruction pointers
-    handler_info::Union{Nothing,HandlerInfo}
+    handler_info::Union{Nothing,HandlerInfo{TryCatchFrame}}
     ssavalue_uses::Vector{BitSet} # ssavalue sparsity and restart info
     # TODO: Could keep this sparsely by doing structural liveness analysis ahead of time.
     bb_vartables::Vector{Union{Nothing,VarTable}} # nothing if not analyzed yet
@@ -318,7 +331,7 @@ mutable struct InferenceState
 
         currbb = currpc = 1
         ip = BitSet(1) # TODO BitSetBoundedMinPrioritySet(1)
-        handler_info = compute_trycatch(code)
+        handler_info = ComputeTryCatch{TryCatchFrame}()(code)
         nssavalues = src.ssavaluetypes::Int
         ssavalue_uses = find_ssavalue_uses(code, nssavalues)
         nstmts = length(code)
@@ -421,10 +434,16 @@ is_inferred(result::InferenceResult) = result.result !== nothing
 
 was_reached(sv::InferenceState, pc::Int) = sv.ssavaluetypes[pc] !== NOT_FOUND
 
-compute_trycatch(ir::IRCode) = compute_trycatch(ir.stmts.stmt, ir.cfg.blocks)
+struct ComputeTryCatch{T<:Handler} end
+
+const compute_trycatch = ComputeTryCatch{SimpleHandler}()
+
+(compute_trycatch::ComputeTryCatch{SimpleHandler})(ir::IRCode) =
+    compute_trycatch(ir.stmts.stmt, ir.cfg.blocks)
 
 """
-    compute_trycatch(code, [, bbs]) -> handler_info::Union{Nothing,HandlerInfo}
+    (::ComputeTryCatch{Handler})(code, [, bbs]) -> handler_info::Union{Nothing,HandlerInfo{Handler}}
+    const compute_trycatch = ComputeTryCatch{SimpleHandler}()
 
 Given the code of a function, compute, at every statement, the current
 try/catch handler, and the current exception stack top. This function returns
@@ -433,9 +452,9 @@ a tuple of:
     1. `handler_info.handler_at`: A statement length vector of tuples
        `(catch_handler, exception_stack)`, which are indices into `handlers`
 
-    2. `handler_info.handlers`: A `TryCatchFrame` vector of handlers
+    2. `handler_info.handlers`: A `Handler` vector of handlers
 """
-function compute_trycatch(code::Vector{Any}, bbs::Union{Vector{BasicBlock},Nothing}=nothing)
+function (::ComputeTryCatch{Handler})(code::Vector{Any}, bbs::Union{Vector{BasicBlock},Nothing}=nothing) where Handler
     # The goal initially is to record the frame like this for the state at exit:
     # 1: (enter 3) # == 0
     # 3: (expr)    # == 1
@@ -454,10 +473,10 @@ function compute_trycatch(code::Vector{Any}, bbs::Union{Vector{BasicBlock},Nothi
         stmt = code[pc]
         if isa(stmt, EnterNode)
             (;handlers, handler_at) = handler_info =
-                (handler_info === nothing ? HandlerInfo(TryCatchFrame[], fill((0, 0), n)) : handler_info)
+                (handler_info === nothing ? HandlerInfo{Handler}(Handler[], fill((0, 0), n)) : handler_info)
             l = stmt.catch_dest
             (bbs !== nothing) && (l = first(bbs[l].stmts))
-            push!(handlers, TryCatchFrame(Bottom, isdefined(stmt, :scope) ? Bottom : nothing, pc))
+            push!(handlers, Handler(stmt, pc))
             handler_id = length(handlers)
             handler_at[pc + 1] = (handler_id, 0)
             push!(ip, pc + 1)
@@ -526,7 +545,7 @@ function compute_trycatch(code::Vector{Any}, bbs::Union{Vector{BasicBlock},Nothi
                     end
                     cur_hand = cur_stacks[1]
                     for i = 1:l
-                        cur_hand = handler_at[handlers[cur_hand].enter_idx][1]
+                        cur_hand = handler_at[get_enter_idx(handlers[cur_hand])][1]
                     end
                     cur_stacks = (cur_hand, cur_stacks[2])
                     cur_stacks == (0, 0) && break

Compiler/src/ssair/slot2ssa.jl

@@ -801,9 +801,11 @@ function construct_ssa!(ci::CodeInfo, ir::IRCode, sv::OptimizationState,
                         has_pinode[id] = false
                         enter_idx = idx
                         while (handler = gethandler(handler_info, enter_idx)) !== nothing
-                            (; enter_idx) = handler
-                            leave_block = block_for_inst(cfg, (code[enter_idx]::EnterNode).catch_dest)
-                            cidx = findfirst((; slot)::NewPhiCNode2->slot_id(slot)==id, new_phic_nodes[leave_block])
+                            enter_idx = get_enter_idx(handler)
+                            enter_node = code[enter_idx]::EnterNode
+                            leave_block = block_for_inst(cfg, enter_node.catch_dest)
+                            cidx = findfirst((; slot)::NewPhiCNode2->slot_id(slot)==id,
+                                new_phic_nodes[leave_block])
                             if cidx !== nothing
                                 node = thisdef ? UpsilonNode(thisval) : UpsilonNode()
                                 if incoming_vals[id] === UNDEF_TOKEN

Compiler/test/inference.jl

@@ -4436,7 +4436,7 @@ let x = Tuple{Int,Any}[
         #=20=# (0, Core.ReturnNode(Core.SlotNumber(3)))
     ]
     (;handler_at, handlers) = Compiler.compute_trycatch(last.(x))
-    @test map(x->x[1] == 0 ? 0 : handlers[x[1]].enter_idx, handler_at) == first.(x)
+    @test map(x->x[1] == 0 ? 0 : Compiler.get_enter_idx(handlers[x[1]]), handler_at) == first.(x)
 end
 
 @test only(Base.return_types((Bool,)) do y