rexcode/x86: generate the encode-recipe table (drop the @init interim)

Move ENCODE_RECIPES from a startup-built (@init) static table in the library to
a generated, #loaded table like every other one. The tablegen runs
form_to_recipe over every form, serializes to x86.encode_recipes.bin, and the
loader #loads it -- no @init, no allocation; the forms remain the single source
of truth and the recipe is derived from them.

- tablegen/gen.odin: ENCODE_RECIPES added to the BLOBS manifest (which drives
  both the Stage B serializer and the loader's #load); emit the generated-package
  global plus an @init that fills it from ENCODE_FORMS via lib.form_to_recipe.
- encoder_recipe.odin: drop the @init, the static storage, and the ENCODE_RECIPES
  declaration. form_to_recipe stays -- now solely the tablegen-time derivation.
- tables.odin, generated/{encode_tables,writer}.odin: regenerated.
- tables/x86.encode_recipes.bin: the generated blob (28260 bytes = 2355 x 12).

No behavior change: the recipes are identical to the @init ones. gen / builders /
check / test / idempotent green (2282 cases, 22 byte-stable artifacts); encode
perf unchanged.

core/rexcode/isa/x86/encoder_recipe.odin

@@ -18,10 +18,9 @@ package rexcode_x86
 // marked `eligible = false` and falls back to the existing interpreter, which
 // stays the source of truth for correctness.
 //
-// NOTE(interim): ENCODE_RECIPES is currently built at startup from the #loaded
-// ENCODE_FORMS (static storage, no heap). Once the fast path is validated this
-// moves into the table generator -- serialized and #loaded like every other
-// table, with no @init.
+// ENCODE_RECIPES is produced by the tablegen (form_to_recipe over every form)
+// and #loaded from x86.encode_recipes.bin like every other table -- see the note
+// by form_to_recipe below.
 
 Form_Recipe :: struct {
 	prefix:     u8,      // mandatory legacy prefix emitted before REX (0 = none)
@@ -121,23 +120,10 @@ form_to_recipe :: proc "contextless" (enc: ^Encoding) -> (r: Form_Recipe) {
 	return
 }
 
-// -----------------------------------------------------------------------------
-// Interim recipe table: built once at startup from the #loaded forms into static
-// storage (no heap). ENCODE_RECIPES is parallel to ENCODE_FORMS.
-// -----------------------------------------------------------------------------
-
-@(private) ENCODE_RECIPE_CAP :: 4096
-@(private) encode_recipes_storage: [ENCODE_RECIPE_CAP]Form_Recipe
-ENCODE_RECIPES: []Form_Recipe
-
-@(init)
-build_encode_recipes :: proc "contextless" () {
-	n := min(len(ENCODE_FORMS), ENCODE_RECIPE_CAP)
-	for i in 0..<n {
-		encode_recipes_storage[i] = form_to_recipe(&ENCODE_FORMS[i])
-	}
-	ENCODE_RECIPES = encode_recipes_storage[:n]
-}
+// ENCODE_RECIPES (parallel to ENCODE_FORMS) is generated, not built here: the
+// tablegen runs form_to_recipe over every form, serializes the result to
+// x86.encode_recipes.bin, and tables.odin #loads it. So form_to_recipe above is
+// a tablegen-time helper -- it is not called on the encode hot path.
 
 @(private)
 op_is_spl :: #force_inline proc "contextless" (op: ^Operand) -> bool {

core/rexcode/isa/x86/tablegen/gen.odin

@@ -44,8 +44,9 @@ Blob :: struct { global, file, typ: string }
 
 @(rodata)
 BLOBS := [?]Blob{
-	{"ENCODE_FORMS",          "x86.encode_forms.bin", "Encoding"},
-	{"ENCODE_RUNS",           "x86.encode_runs.bin",  "Encode_Run"},
+	{"ENCODE_FORMS",          "x86.encode_forms.bin",   "Encoding"},
+	{"ENCODE_RUNS",           "x86.encode_runs.bin",    "Encode_Run"},
+	{"ENCODE_RECIPES",        "x86.encode_recipes.bin", "Form_Recipe"},
 	{"MODRM_TABLE",           "x86.modrm.bin",        "ModRM_Info"},
 	{"SIB_TABLE",             "x86.sib.bin",          "SIB_Info"},
 	{"LEGACY_DECODE_ENTRIES", "x86.legacy.bin",       "Decode_Entry"},
@@ -123,6 +124,18 @@ emit_encode_tables :: proc() {
 		start += n
 	}
 	strings.write_string(&sb, "}\n")
+
+	// Emit descriptor per form: the flattened recipe the encoder replays, derived
+	// from the forms via the library's form_to_recipe (single source of truth).
+	// Filled here at startup and serialized to x86.encode_recipes.bin; the loader
+	// #loads it, so the library itself needs no @init.
+	strings.write_string(&sb, "\n// Emit descriptor per form (derived from ENCODE_FORMS via lib.form_to_recipe).\n")
+	fmt.sbprintfln(&sb, "ENCODE_RECIPES: [%d]lib.Form_Recipe", total_forms())
+	strings.write_string(&sb, "@(init) _fill_recipes :: proc \"contextless\" () {\n")
+	strings.write_string(&sb, "\tfor i in 0 ..< len(ENCODE_FORMS) {\n")
+	strings.write_string(&sb, "\t\tENCODE_RECIPES[i] = lib.form_to_recipe(&ENCODE_FORMS[i])\n")
+	strings.write_string(&sb, "\t}\n}\n")
+
 	emit_file(DIR_GEN + "encode_tables.odin", &sb)
 }
 

core/rexcode/isa/x86/tablegen/generated/encode_tables.odin

@@ -4720,3 +4720,11 @@ ENCODE_RUNS := [lib.Mnemonic]lib.Encode_Run{
 	.RDRAND           = { 2349,   3},
 	.RDSEED           = { 2352,   3},
 }
+
+// Emit descriptor per form (derived from ENCODE_FORMS via lib.form_to_recipe).
+ENCODE_RECIPES: [2355]lib.Form_Recipe
+@(init) _fill_recipes :: proc "contextless" () {
+	for i in 0 ..< len(ENCODE_FORMS) {
+		ENCODE_RECIPES[i] = lib.form_to_recipe(&ENCODE_FORMS[i])
+	}
+}

core/rexcode/isa/x86/tablegen/generated/writer.odin

@@ -24,6 +24,7 @@ w :: proc(file: string, data: []u8) {
 main :: proc() {
 	w(TABLES + "x86.encode_forms.bin", raw(&ENCODE_FORMS, size_of(ENCODE_FORMS)))
 	w(TABLES + "x86.encode_runs.bin", raw(&ENCODE_RUNS, size_of(ENCODE_RUNS)))
+	w(TABLES + "x86.encode_recipes.bin", raw(&ENCODE_RECIPES, size_of(ENCODE_RECIPES)))
 	w(TABLES + "x86.modrm.bin", raw(&MODRM_TABLE, size_of(MODRM_TABLE)))
 	w(TABLES + "x86.sib.bin", raw(&SIB_TABLE, size_of(SIB_TABLE)))
 	w(TABLES + "x86.legacy.bin", raw(&LEGACY_DECODE_ENTRIES, size_of(LEGACY_DECODE_ENTRIES)))

core/rexcode/isa/x86/tables.odin

@@ -76,23 +76,24 @@ Decode_Index :: struct {
 // Loaded tables (rodata, embedded from tables/*.bin at compile time)
 // -----------------------------------------------------------------------------
 
-@(rodata) ENCODE_FORMS          := #load("tables/x86.encode_forms.bin",  []Encoding)
-@(rodata) ENCODE_RUNS           := #load("tables/x86.encode_runs.bin",   []Encode_Run)
-@(rodata) MODRM_TABLE           := #load("tables/x86.modrm.bin",         []ModRM_Info)
-@(rodata) SIB_TABLE             := #load("tables/x86.sib.bin",           []SIB_Info)
-@(rodata) LEGACY_DECODE_ENTRIES := #load("tables/x86.legacy.bin",        []Decode_Entry)
-@(rodata) VEX_DECODE_ENTRIES    := #load("tables/x86.vex.bin",           []VEX_Decode_Entry)
-@(rodata) EVEX_DECODE_ENTRIES   := #load("tables/x86.evex.bin",          []VEX_Decode_Entry)
-@(rodata) DECODE_INDEX_LEGACY   := #load("tables/x86.idx_legacy.bin",    []Decode_Index)
-@(rodata) DECODE_INDEX_ESC_0F   := #load("tables/x86.idx_0f.bin",        []Decode_Index)
-@(rodata) DECODE_INDEX_ESC_0F38 := #load("tables/x86.idx_0f38.bin",      []Decode_Index)
-@(rodata) DECODE_INDEX_ESC_0F3A := #load("tables/x86.idx_0f3a.bin",      []Decode_Index)
-@(rodata) VEX_INDEX_0F          := #load("tables/x86.vex_idx_0f.bin",    []Decode_Index)
-@(rodata) VEX_INDEX_0F38        := #load("tables/x86.vex_idx_0f38.bin",  []Decode_Index)
-@(rodata) VEX_INDEX_0F3A        := #load("tables/x86.vex_idx_0f3a.bin",  []Decode_Index)
-@(rodata) EVEX_INDEX_0F         := #load("tables/x86.evex_idx_0f.bin",   []Decode_Index)
-@(rodata) EVEX_INDEX_0F38       := #load("tables/x86.evex_idx_0f38.bin", []Decode_Index)
-@(rodata) EVEX_INDEX_0F3A       := #load("tables/x86.evex_idx_0f3a.bin", []Decode_Index)
+@(rodata) ENCODE_FORMS          := #load("tables/x86.encode_forms.bin",   []Encoding)
+@(rodata) ENCODE_RUNS           := #load("tables/x86.encode_runs.bin",    []Encode_Run)
+@(rodata) ENCODE_RECIPES        := #load("tables/x86.encode_recipes.bin", []Form_Recipe)
+@(rodata) MODRM_TABLE           := #load("tables/x86.modrm.bin",          []ModRM_Info)
+@(rodata) SIB_TABLE             := #load("tables/x86.sib.bin",            []SIB_Info)
+@(rodata) LEGACY_DECODE_ENTRIES := #load("tables/x86.legacy.bin",         []Decode_Entry)
+@(rodata) VEX_DECODE_ENTRIES    := #load("tables/x86.vex.bin",            []VEX_Decode_Entry)
+@(rodata) EVEX_DECODE_ENTRIES   := #load("tables/x86.evex.bin",           []VEX_Decode_Entry)
+@(rodata) DECODE_INDEX_LEGACY   := #load("tables/x86.idx_legacy.bin",     []Decode_Index)
+@(rodata) DECODE_INDEX_ESC_0F   := #load("tables/x86.idx_0f.bin",         []Decode_Index)
+@(rodata) DECODE_INDEX_ESC_0F38 := #load("tables/x86.idx_0f38.bin",       []Decode_Index)
+@(rodata) DECODE_INDEX_ESC_0F3A := #load("tables/x86.idx_0f3a.bin",       []Decode_Index)
+@(rodata) VEX_INDEX_0F          := #load("tables/x86.vex_idx_0f.bin",     []Decode_Index)
+@(rodata) VEX_INDEX_0F38        := #load("tables/x86.vex_idx_0f38.bin",   []Decode_Index)
+@(rodata) VEX_INDEX_0F3A        := #load("tables/x86.vex_idx_0f3a.bin",   []Decode_Index)
+@(rodata) EVEX_INDEX_0F         := #load("tables/x86.evex_idx_0f.bin",    []Decode_Index)
+@(rodata) EVEX_INDEX_0F38       := #load("tables/x86.evex_idx_0f38.bin",  []Decode_Index)
+@(rodata) EVEX_INDEX_0F3A       := #load("tables/x86.evex_idx_0f3a.bin",  []Decode_Index)
 
 // -----------------------------------------------------------------------------
 // Accessors