Value::MulHi and constant propagation for OPCODE_MUL_HI. Could maybe be reworked?

src/xenia/cpu/compiler/passes/constant_propagation_pass.cc

@@ -354,6 +354,13 @@ bool ConstantPropagationPass::Run(HIRBuilder* builder) {
             i->Remove();
           }
           break;
+        case OPCODE_MUL_HI:
+          if (i->src1.value->IsConstant() && i->src2.value->IsConstant()) {
+            v->set_from(i->src1.value);
+            v->MulHi(i->src2.value, (i->flags & ARITHMETIC_UNSIGNED) != 0);
+            i->Remove();
+          }
+          break;
         case OPCODE_DIV:
           if (i->src1.value->IsConstant() && i->src2.value->IsConstant()) {
             v->set_from(i->src1.value);

src/xenia/cpu/hir/value.cc

@@ -304,6 +304,29 @@ void Value::Mul(Value* other) {
   }
 }
 
+void Value::MulHi(Value* other, bool is_unsigned) {
+  assert_true(type == other->type);
+  switch (type) {
+    case INT32_TYPE:
+      if (is_unsigned) {
+        constant.i32 = (int32_t)(((uint64_t)((uint32_t)constant.i32) * (uint32_t)other->constant.i32) >> 32);
+      } else {
+        constant.i32 = (int32_t)(((int64_t)constant.i32 * (int64_t)other->constant.i32) >> 32);
+      }
+      break;
+    case INT64_TYPE:
+      if (is_unsigned) {
+        constant.i64 = __umulh(constant.i64, other->constant.i64);
+      } else {
+        constant.i64 = __mulh(constant.i64, other->constant.i64);
+      }
+      break;
+    default:
+      assert_unhandled_case(type);
+      break;
+  }
+}
+
 void Value::Div(Value* other, bool is_unsigned) {
   assert_true(type == other->type);
   switch (type) {

src/xenia/cpu/hir/value.h

@@ -385,6 +385,7 @@ class Value {
   bool Add(Value* other);
   bool Sub(Value* other);
   void Mul(Value* other);
+  void MulHi(Value* other, bool is_unsigned);
   void Div(Value* other, bool is_unsigned);
   static void MulAdd(Value* dest, Value* value1, Value* value2, Value* value3);
   static void MulSub(Value* dest, Value* value1, Value* value2, Value* value3);