feat: optimize fallback and text receivers opcode parsing

dev-docs/CHANGELOG.md

@@ -11,6 +11,7 @@ The documentation changelog is kept separately: [CHANGELOG-DOCS](./CHANGELOG-DOC
 
 ### Code generation
 
+- Optimized opcode parsing for fallback and text receivers: PR [#3331](https://github.com/tact-lang/tact/pull/3331)
 - Reordered arguments of the `__tact_store_address_opt` function to optimize gas consumption: PR [#3333](https://github.com/tact-lang/tact/pull/3333)
 
 ## [1.6.13] - 2025-05-29

src/benchmarks/nft/gas.json

@@ -199,6 +199,16 @@
         "deploy nft": "10299",
         "batch deploy nft": "650666"
       }
+    },
+    {
+      "label": "1.6.13 with optimized opcode parsing for fallback and text receivers",
+      "pr": "https://github.com/tact-lang/tact/pull/3331",
+      "gas": {
+        "transfer": "6907",
+        "get static data": "4388",
+        "deploy nft": "10263",
+        "batch deploy nft": "648848"
+      }
     }
   ]
 }

src/benchmarks/nft/size.json

@@ -209,6 +209,16 @@
         "item cells": "10",
         "item bits": "5185"
       }
+    },
+    {
+      "label": "1.6.13 with optimized opcode parsing for fallback and text receivers",
+      "pr": "https://github.com/tact-lang/tact/pull/3331",
+      "size": {
+        "collection cells": "39",
+        "collection bits": "19564",
+        "item cells": "10",
+        "item bits": "5185"
+      }
     }
   ]
 }

src/benchmarks/sbt/gas.json

@@ -181,6 +181,19 @@
         "revoke": "3778",
         "take excess": "5577"
       }
+    },
+    {
+      "label": "1.6.13 with optimized opcode parsing for fallback and text receivers",
+      "pr": "https://github.com/tact-lang/tact/pull/3331",
+      "gas": {
+        "deploy": "3940",
+        "request owner": "4848",
+        "prove ownership": "5026",
+        "get static data": "4678",
+        "destroy": "6125",
+        "revoke": "3742",
+        "take excess": "5541"
+      }
     }
   ]
 }

src/generator/writers/writeRouter.ts

@@ -130,15 +130,15 @@ export function writeNonBouncedRouter(
         receivers.comment.length > 0 ||
         typeof receivers.commentFallback !== "undefined";
 
-    wCtx.append("int op = 0;");
     wCtx.append("int in_msg_length = slice_bits(in_msg);");
-    wCtx.inBlock("if (in_msg_length >= 32)", () => {
-        wCtx.append(`op = in_msg${opcodeReader}(32);`);
-
-        if (doesHaveTextReceivers) {
+    wCtx.append(
+        `int op = (in_msg_length >= 32) ? in_msg${opcodeReader}(32) : 0;`,
+    );
+    if (doesHaveTextReceivers) {
+        wCtx.inBlock("if (in_msg_length >= 32)", () => {
             writeBinaryReceivers(opcodeReader === "~load_uint");
-        }
-    });
+        });
+    }
 
     // NOTE: It should be more efficient to write all binary receivers inside
     //       `in_msg_length` length if-check regardless of text receivers,

src/test/codegen-check/__snapshots__/codegen.test.ts.snap

@@ -577,10 +577,9 @@ _ %asSlice() method_id(68231) {
 
     ;; Handle bounced messages
     if (msg_bounced) { return (); }
-    int op = 0;
     int in_msg_length = slice_bits(in_msg);
+    int op = (in_msg_length >= 32) ? in_msg~load_uint(32) : 0;
     if (in_msg_length >= 32) {
-        op = in_msg~load_uint(32);
         ;; Receive Bin message
         if (op == 0x2) {
             var $m = empty_tuple();

src/test/e2e-emulated/debug/__snapshots__/dump.spec.ts.snap

@@ -3,7 +3,7 @@
 exports[`dump should dump values correctly in a receiver 1`] = `
 "#DEBUG#: File src/test/e2e-emulated/debug/dump.tact:2:5:
 #DEBUG#: dumpStack()
-#DEBUG#: stack(1 values) : 10999604800 
+#DEBUG#: stack(1 values) : 10999556400 
 #DEBUG#: File src/test/e2e-emulated/debug/dump.tact:3:5:
 #DEBUG#: dump("Hello world!")
 #DEBUG#: Hello world!
@@ -21,13 +21,13 @@ exports[`dump should dump values correctly in a receiver 1`] = `
 #DEBUG#: null
 #DEBUG#: File src/test/e2e-emulated/debug/dump.tact:8:5:
 #DEBUG#: dump(myAddress())
-#DEBUG#: EQBW6PMGWgu6Gmg_pFckrGpQxm2ImeVELrquQXN0FaneV9fj
+#DEBUG#: EQAOdLgPqDU7Iakg-03LKk-3VfNPuNtiCnNLn9bpfYYCG-Tl
 #DEBUG#: File src/test/e2e-emulated/debug/dump.tact:10:5:
 #DEBUG#: dump(address)
 #DEBUG#: EQCD39VS5jcptHL8vMjEXrzGaRcCVYto7HUn4bpAOg8xqB2N
 #DEBUG#: File src/test/e2e-emulated/debug/dump.tact:11:5:
 #DEBUG#: dump(myBalance())
-#DEBUG#: 10999604800
+#DEBUG#: 10999556400
 #DEBUG#: File src/test/e2e-emulated/debug/dump.tact:15:5:
 #DEBUG#: dump(maybeBool1)
 #DEBUG#: null

src/test/gas-consumption/__snapshots__/gas.spec.ts.snap

@@ -38,23 +38,23 @@ exports[`benchmarks benchmark readFwdFee: code size 1`] = `116`;
 
 exports[`benchmarks benchmark readFwdFee: gas used 1`] = `1968`;
 
-exports[`benchmarks benchmark sha256: gas hash string big 1`] = `2154`;
+exports[`benchmarks benchmark sha256: gas hash string big 1`] = `2126`;
 
-exports[`benchmarks benchmark sha256: gas hash string big repeated 1`] = `2155`;
+exports[`benchmarks benchmark sha256: gas hash string big repeated 1`] = `2127`;
 
-exports[`benchmarks benchmark sha256: gas hash string big repeated more 1`] = `2157`;
+exports[`benchmarks benchmark sha256: gas hash string big repeated more 1`] = `2129`;
 
-exports[`benchmarks benchmark sha256: gas hash string slice 1`] = `2154`;
+exports[`benchmarks benchmark sha256: gas hash string slice 1`] = `2126`;
 
-exports[`benchmarks benchmark sha256: gas hash string slice repeated 1`] = `2155`;
+exports[`benchmarks benchmark sha256: gas hash string slice repeated 1`] = `2127`;
 
-exports[`benchmarks benchmark sha256: gas hash string slice repeated more 1`] = `2157`;
+exports[`benchmarks benchmark sha256: gas hash string slice repeated more 1`] = `2129`;
 
-exports[`benchmarks benchmark sha256: gas hash string small 1`] = `1975`;
+exports[`benchmarks benchmark sha256: gas hash string small 1`] = `1947`;
 
-exports[`benchmarks benchmark sha256: gas hash string small repeated 1`] = `1975`;
+exports[`benchmarks benchmark sha256: gas hash string small repeated 1`] = `1947`;
 
-exports[`benchmarks benchmark sha256: gas hash string small repeated more 1`] = `1975`;
+exports[`benchmarks benchmark sha256: gas hash string small repeated more 1`] = `1947`;
 
 exports[`benchmarks benchmark sqrt via geom mean: code size 1`] = `265`;