[Tolk] Peephole optimization: SDSKIPFIRST to LDU+NIP

It's a bit better for gas usage, always

Author: tolk-vm

tolk-tester/tests/cells-slices.tolk

@@ -401,8 +401,8 @@ We test that consequtive storeInt/storeUint with constants are joined into a sin
 @fif_codegen
 """
   test21() PROC:<{
-    14 PUSHINT
-    SDSKIPFIRST
+    14 LDU
+    NIP
   }>
 """
 

tolk-tester/tests/lazy-load-tests.tolk

@@ -1741,8 +1741,8 @@ fun main() {
 """
   demo103() PROC:<{             //
     x{0102} PUSHSLICE           //  lazyS
-    8 PUSHINT
-    SDSKIPFIRST                 //  lazyS
+    8 LDU
+    NIP                         //  lazyS
     8 LDI                       //  '10 lazyS
     DROP                        //  p.y
 """
@@ -1753,17 +1753,17 @@ fun main() {
                                 //  lazyS
     PUSHNULL                    //  lazyS x
     SWAP                        //  x lazyS
-    8 PUSHINT
-    SDSKIPFIRST                 //  x lazyS
+    8 LDU
+    NIP                         //  x lazyS
     1 LDU                       //  x '18 lazyS
 """
 
 @fif_codegen
 """
   demo109() PROC:<{             //
     x{8000003d800000e4000000000000000000000000000000000000000000000000000000000000000020_} PUSHSLICE    //  lazyS
-    65 PUSHINT
-    SDSKIPFIRST                 //  lazyS
+    65 LDU
+    NIP                         //  lazyS
     256 LDU                     //  '13 lazyS
     DROP                        //  st.publicKey
   }>
@@ -1821,8 +1821,8 @@ fun main() {
       DROP
       -1 PUSHINT
     }>
-    8 PUSHINT
-    SDSKIPFIRST
+    8 LDU
+    NIP
     8 LDI
     DROP
   }>
@@ -1962,8 +1962,8 @@ fun main() {
           THROWANY
         }>
         32 LDU
-        8 PUSHINT
-        SDSKIPFIRST
+        8 LDU
+        NIP
         8 LDI
         DROP
         OVER

tolk-tester/tests/pack-unpack-1.tolk

@@ -112,8 +112,8 @@ fun main(c: cell) {
     64 STI                      //  b
     ENDC                        //  c
     CTOS                        //  s
-    64 PUSHINT
-    SDSKIPFIRST                 //  s
+    64 LDU
+    NIP                         //  s
     SBITS                       //  '17
   }>
 """

tolk/optimize.cpp

@@ -231,8 +231,13 @@ bool Optimizer::detect_rewrite_MY_skip_bits() {
 
   p_ = n_merged;
   q_ = 2;
-  oq_[0] = std::make_unique<AsmOp>(AsmOp::IntConst(op_[0]->loc, td::make_refint(total_skip_bits)));
-  oq_[1] = std::make_unique<AsmOp>(AsmOp::Custom(op_[0]->loc, "SDSKIPFIRST"));
+  if (total_skip_bits <= 256) {
+    oq_[0] = std::make_unique<AsmOp>(AsmOp::Custom(op_[0]->loc, std::to_string(total_skip_bits) + " LDU"));
+    oq_[1] = std::make_unique<AsmOp>(AsmOp::Pop(op_[0]->loc, 1));
+  } else {
+    oq_[0] = std::make_unique<AsmOp>(AsmOp::IntConst(op_[0]->loc, td::make_refint(total_skip_bits)));
+    oq_[1] = std::make_unique<AsmOp>(AsmOp::Custom(op_[0]->loc, "SDSKIPFIRST"));
+  }
   return true;
 }