Refactoring: Introduce ArgTypesRewrite

gen/abi.cpp

@@ -12,6 +12,7 @@
 #include "dmd/expression.h"
 #include "dmd/id.h"
 #include "dmd/identifier.h"
+#include "dmd/target.h"
 #include "gen/abi-aarch64.h"
 #include "gen/abi-arm.h"
 #include "gen/abi-generic.h"
@@ -67,6 +68,40 @@ bool TargetABI::isHFVA(Type *t, int maxNumElements, LLType **hfvaType) {
   return false;
 }
 
+//////////////////////////////////////////////////////////////////////////////
+
+TypeTuple *TargetABI::getArgTypes(Type *t) {
+  // try to reuse cached argTypes of StructDeclarations
+  if (auto ts = t->toBasetype()->isTypeStruct()) {
+    auto sd = ts->sym;
+    if (sd->sizeok == SIZEOKdone)
+      return sd->argTypes;
+  }
+
+  return target.toArgTypes(t);
+}
+
+LLType *TargetABI::getRewrittenArgType(Type *t, TypeTuple *argTypes) {
+  if (!argTypes || argTypes->arguments->empty() ||
+      (argTypes->arguments->length == 1 &&
+       argTypes->arguments->front()->type == t)) {
+    return nullptr; // don't rewrite
+  }
+
+  auto &args = *argTypes->arguments;
+  assert(args.length <= 2);
+  return args.length == 1
+             ? DtoType(args[0]->type)
+             : LLStructType::get(gIR->context(), {DtoType(args[0]->type),
+                                                  DtoType(args[1]->type)});
+}
+
+LLType *TargetABI::getRewrittenArgType(Type *t) {
+  return getRewrittenArgType(t, getArgTypes(t));
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
 bool TargetABI::isAggregate(Type *t) {
   TY ty = t->toBasetype()->ty;
   // FIXME: dynamic arrays can currently not be rewritten as they are used