[llvm] Introduce DIExpressionOptimizer (PR #69769)

[Adrian Prantl via llvm-commits]

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@@ -1734,6 +1734,143 @@ const DIExpression *DIExpression::extractAddressClass(const DIExpression *Expr,
   return Expr;
 }
 
+SmallVector<uint64_t>
+DIExpressionOptimizer::getOperatorLocations(ArrayRef<uint64_t> Ops) {
+  SmallVector<uint64_t> OpLocs;
+  uint64_t Loc = 0;
+  DIExpressionCursor Cursor(Ops);
+
+  while (Cursor.peek()) {
+    OpLocs.push_back(Loc);
+    auto Size = Cursor.peek()->getSize();
+    Loc += Size;
+    Cursor.consume(1);
+  }
+
+  return OpLocs;
+}
+
+bool DIExpressionOptimizer::operatorIsCommutative(uint64_t Operator) {
+  return Operator == dwarf::DW_OP_mul || Operator == dwarf::DW_OP_plus;
+}
+
+bool DIExpressionOptimizer::operatorCanBeOptimized(uint64_t Operator) {
+  switch (Operator) {
+  case dwarf::DW_OP_plus:
+  case dwarf::DW_OP_plus_uconst:
+  case dwarf::DW_OP_minus:
+  case dwarf::DW_OP_mul:
+  case dwarf::DW_OP_div:
+  case dwarf::DW_OP_shl:
+  case dwarf::DW_OP_shr:
+    return true;
+  default:
+    return false;
+  }
+}
+
+void DIExpressionOptimizer::reset() {
+  NewMathOperator = 0;
+  CurrMathOperator = 0;
+  OperatorLeft = 0;
+  OperatorRight = 0;
+}
+
+void DIExpressionOptimizer::optimize(SmallVectorImpl<uint64_t> &NewOps,
+                                     ArrayRef<uint64_t> Ops) {
+
+  if (Ops.size() == 2 && Ops[0] == dwarf::DW_OP_plus_uconst) {
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adrian-prantl wrote:

Why == 2 and not >= 2?

https://github.com/llvm/llvm-project/pull/69769