optimizer: collapse mov loops

Author: ckrause

CHANGELOG.md

@@ -2,9 +2,11 @@ To install or update LODA, please follow the [installation instructions](https:/
 
 ## [Unreleased]
 
+## v24.9.7
+
 ### Bugfixes
 
-* Fix optimizer `prg`-handling
+* Fix optimizer `prg` handling
 * Fix max memory option `-m`
 * Fix program folding
 
@@ -13,6 +15,7 @@ To install or update LODA, please follow the [installation instructions](https:/
 * Support `prg` in `unfold` command
 * Internal `replace` command
 * Remove deprecated dot export
+* Collapse `mov` loops in optimizer
 
 ## v24.9.2
 

src/lang/optimizer.cpp

@@ -52,7 +52,10 @@ bool Optimizer::optimize(Program &p) const {
     if (mergeLoops(p)) {
       changed = true;
     }
-    if (collapseLoops(p)) {
+    if (collapseMovLoops(p)) {
+      changed = true;
+    }
+    if (collapseArithmeticLoops(p)) {
       changed = true;
     }
     if (pullUpMov(p)) {
@@ -768,7 +771,42 @@ bool Optimizer::mergeLoops(Program &p) const {
   return false;
 }
 
-bool Optimizer::collapseLoops(Program &p) const {
+bool Optimizer::collapseMovLoops(Program &p) const {
+  bool changed = false;
+  for (size_t i = 0; i + 2 < p.ops.size(); i++) {
+    if (p.ops[i].type != Operation::Type::LPB ||
+        p.ops[i + 1].type != Operation::Type::MOV ||
+        p.ops[i + 2].type != Operation::Type::LPE) {
+      continue;
+    }
+    const auto &lpb = p.ops[i];
+    const auto &mov = p.ops[i + 1];
+    if (lpb.source != Operand(Operand::Type::CONSTANT, 1) ||
+        lpb.target.type != Operand::Type::DIRECT ||
+        mov.source.type != Operand::Type::CONSTANT ||
+        mov.target != lpb.target) {
+      continue;
+    }
+    auto val = mov.source.value;
+    if (val < Number::ZERO) {
+      p.ops.erase(p.ops.begin() + i, p.ops.begin() + i + 3);
+      changed = true;
+    } else if (val == Number::ZERO) {
+      p.ops.erase(p.ops.begin() + i + 1, p.ops.begin() + i + 3);
+      p.ops[i] = Operation(Operation::Type::MOV, lpb.target,
+                           Operand(Operand::Type::CONSTANT, 0));
+      changed = true;
+    } else {
+      p.ops.erase(p.ops.begin() + i + 1, p.ops.begin() + i + 3);
+      p.ops[i] = Operation(Operation::Type::MIN, lpb.target,
+                           Operand(Operand::Type::CONSTANT, val));
+      changed = true;
+    }
+  }
+  return changed;
+}
+
+bool Optimizer::collapseArithmeticLoops(Program &p) const {
   if (ProgramUtil::hasIndirectOperand(p)) {
     return false;
   }

src/lang/optimizer.hpp

@@ -31,7 +31,9 @@ class Optimizer {
 
   bool mergeLoops(Program &p) const;
 
-  bool collapseLoops(Program &p) const;
+  bool collapseMovLoops(Program &p) const;
+
+  bool collapseArithmeticLoops(Program &p) const;
 
   bool pullUpMov(Program &p) const;
 

src/lang/program_util.cpp

@@ -217,11 +217,12 @@ bool ProgramUtil::getUsedMemoryCells(const Program &p,
   for (const auto &op : p.ops) {
     int64_t region_length = 1;
     if (op.source.type == Operand::Type::INDIRECT ||
-        op.target.type == Operand::Type::INDIRECT) {
+        op.target.type == Operand::Type::INDIRECT ||
+        op.type == Operation::Type::PRG) {
       return false;
     }
-    if (op.type == Operation::Type::LPB ||
-        ProgramUtil::isWritingRegion(op.type)) {
+    if (op.type == Operation::Type::LPB || op.type == Operation::Type::CLR ||
+        op.type == Operation::Type::SRT) {
       if (op.source.type == Operand::Type::CONSTANT) {
         region_length = op.source.value.asInt();
       } else {

tests/optimizer/E046.asm

@@ -0,0 +1,10 @@
+; in
+add $0,3
+lpb $0
+  mov $0,120
+lpe
+div $0,2
+; out
+add $0,3
+min $0,120
+div $0,2

tests/optimizer/E047.asm

@@ -0,0 +1,8 @@
+; in
+add $0,3
+lpb $0
+  mov $0,0
+lpe
+add $0,7
+; out
+mov $0,7

tests/optimizer/E048.asm

@@ -0,0 +1,8 @@
+; in
+add $0,3
+lpb $0
+  mov $0,-3
+lpe
+add $0,7
+; out
+add $0,10