void ReturnByRef::returnByRefCollectCalls(RefMap& calls, FnSet& fns)
{
RefMap::iterator iter;
forv_Vec(CallExpr, call, gCallExprs)
{
// Only transform calls that are still in the AST tree
// (defer statement bodies have been removed at this point
// in this pass)
if (call->inTree()) {
// Only transform calls to transformable functions
// The common case is a user-level call to a resolved function
// Also handle the PRIMOP for a virtual method call
if (FnSymbol* fn = call->resolvedOrVirtualFunction()) {
TransformationKind tfKind = transformableFunctionKind(fn);
if (tfKind == TF_FULL)
{
RefMap::iterator iter = calls.find(fn->id);
ReturnByRef* info = NULL;
if (iter == calls.end())
{
info = new ReturnByRef(fn);
calls[fn->id] = info;
}
else
{
info = iter->second;
}
info->addCall(call);
}
else if (tfKind == TF_ASGN)
{
fns.insert(fn);
}
}
}
}
}
// The argument is assumed to be an assignment function.
// It is deemed to be simple if it contains only 'move', 'addr of', '=',
// 'return' primitives and calls only simple assignments (recursively).
// We also require that it return void (for now).
// The FLAG_TRIVIAL_ASSIGNMENT is used to ensure that we visit each such
// function only once.
static bool isTrivial(FnSymbol* fn, FnSet& visited)
{
// Visit each function only once.
if (visited.find(fn) != visited.end())
{
// Found it.
if (fn->hasFlag(FLAG_TRIVIAL_ASSIGNMENT))
return true;
else
return false;
}
visited.insert(fn);
// We assume that compiler-generated assignments are field-by-field copies.
// Note that this overloads the meaning of this flag with:
// "Assignment operations flagged as 'compiler generated' shall contain only
// field assignments and assignment primitives."
// We can then assume that all nested calls are field extractions or
// assignments, and we only have to check the latter.
if (! fn->hasFlag(FLAG_COMPILER_GENERATED))
return false;
// After all compiler-supplied assignments use the new signature, this can
// become an assert.
if (fn->retType != dtVoid)
return false;
// The base argument types must match.
ArgSymbol* lhs = fn->getFormal(1);
ArgSymbol* rhs = fn->getFormal(2);
if (lhs->type->getValType() != rhs->type->getValType())
return false;
// Assume this is a field-by-field copy.
// If none of the fields of this record (or tuple) has a user-defined
// assignment (recursively), then it can be replaced by a bulk copy.
// Traverse the call expressions in the body of the function.
// These should all be one of the allowed primitives or calls to simple
// assignments. If anything else, the assignment is "interesting", and
// cannot be replaced.
std::vector<BaseAST*> asts;
collect_asts_STL(fn->body, asts);
for_vector(BaseAST, ast, asts)
{
if (CallExpr* call = toCallExpr(ast))
{
if (FnSymbol* fieldAsgn = call->isResolved())
{
if (isAssignment(fieldAsgn))
if (! isTrivial(fieldAsgn, visited))
return false;
}
else
{
// This is a primitive.
switch(call->primitive->tag)
{
default:
return false;
// These are the allowable primitives.
case PRIM_MOVE:
case PRIM_ASSIGN:
case PRIM_ADDR_OF:
case PRIM_DEREF:
case PRIM_GET_MEMBER:
case PRIM_GET_MEMBER_VALUE:
case PRIM_SET_MEMBER:
case PRIM_RETURN: // We expect return _void.
break;
}
}
}
}
fn->addFlag(FLAG_TRIVIAL_ASSIGNMENT);
return true;
}