add rule to flip lt/gt ops

vyper/venom/basicblock.py

@@ -84,6 +84,8 @@
 
 COMMUTATIVE_INSTRUCTIONS = frozenset(["add", "mul", "smul", "or", "xor", "and", "eq"])
 
+FLIPPABLE_INSTRUCTIONS = ("gt", "lt", "sgt", "slt")
+
 if TYPE_CHECKING:
     from vyper.venom.function import IRFunction
 
@@ -230,6 +232,10 @@ def is_volatile(self) -> bool:
     def is_commutative(self) -> bool:
         return self.opcode in COMMUTATIVE_INSTRUCTIONS
 
+    @property
+    def is_flippable(self) -> bool:
+        return self.opcode in FLIPPABLE_INSTRUCTIONS
+
     @property
     def is_bb_terminator(self) -> bool:
         return self.opcode in BB_TERMINATORS
@@ -282,6 +288,14 @@ def get_outputs(self) -> list[IROperand]:
         """
         return [self.output] if self.output else []
 
+    def flip_operands(self):
+        assert self.is_flippable
+        if self.opcode in ("gt", "sgt"):
+            self.opcode = self.opcode.replace("g", "l")
+        else:
+            self.opcode = self.opcode.replace("l", "g")
+        self.operands.reverse()
+
     def replace_operands(self, replacements: dict) -> None:
         """
         Update operands with replacements.

vyper/venom/passes/dft.py

@@ -23,7 +23,6 @@ def run_pass(self) -> None:
         self.visited_instructions: OrderedSet[IRInstruction] = OrderedSet()
 
         self.dfg = self.analyses_cache.request_analysis(DFGAnalysis)
-        basic_blocks = list(self.function.get_basic_blocks())
 
         for bb in self.function.get_basic_blocks():
             self._process_basic_block(bb)
@@ -66,7 +65,7 @@ def _process_instruction_r(self, instructions: list[IRInstruction], inst: IRInst
 
         def key(x):
             cost = 0
-            if x.output in inst.operands and not inst.is_commutative:
+            if x.output in inst.operands and not inst.is_commutative and not inst.is_flippable:
                 cost = inst.operands.index(x.output)
             return cost - len(self.inst_offspring[x]) * 0.5
 
@@ -76,6 +75,9 @@ def key(x):
         if inst.is_commutative and children != list(self.ida[inst]):
             inst.operands.reverse()
 
+        if inst.is_flippable and children != list(self.ida[inst]):
+            inst.flip_operands()
+
         for dep_inst in children:
             self._process_instruction_r(instructions, dep_inst)