Hi,
I'm porting some existing code of mine to CVS HEAD, and don't understand
something about new RegisterClass TableGen definition:
class RegisterClass<string namespace, list<ValueType> regTypes,........
{
.....
string Namespace = namespace;
What is this "namespace" thing? It looks like it should contain the name of
backend, right?
// RegType - Specify the ValueType of the registers in this register
// class. Note that all registers in a register class must have the same
// ValueType.
list<ValueType> RegTypes = regTypes;
The comment seems out of date -- it says that only one type is allowed,
while list is used. Can somebody explain what would it mean for a register
class to have several allowed ValueTypes?
Thanks,
Volodya
I'm porting some existing code of mine to CVS HEAD, and don't understand
something about new RegisterClass TableGen definition:
class RegisterClass<string namespace, list<ValueType> regTypes,........
{
.....
string Namespace = namespace;
What is this "namespace" thing? It looks like it should contain the name of
backend, right?
Right. This is "X86" "Alpha" "PPC" etc, which is used to prefix register names and other things (PPC::R1 for example). Something short but unique is good.
// RegType - Specify the ValueType of the registers in this register
// class. Note that all registers in a register class must have the same
// ValueType.
list<ValueType> RegTypes = regTypes;
The comment seems out of date -- it says that only one type is allowed,
while list is used.
Thanks, fixed!
Can somebody explain what would it mean for a register
class to have several allowed ValueTypes?
This is useful for targets where multiple types of the same size can be held in the same registers. For example, if the target has a unified register file for Int/FP, it could have [i64, f64]. In practice, this is most useful for vector types, the X86 backend has [v16i8, v8i16, v4i32, v2i64, v4f32, v2f64].
-Chris
Chris Lattner wrote:
// RegType - Specify the ValueType of the registers in this register
// class. Note that all registers in a register class must have the same
// ValueType.
list<ValueType> RegTypes = regTypes;
The comment seems out of date -- it says that only one type is allowed,
while list is used.
Thanks, fixed!
Can somebody explain what would it mean for a register
class to have several allowed ValueTypes?
This is useful for targets where multiple types of the same size can be
held in the same registers. For example, if the target has a unified
register file for Int/FP, it could have [i64, f64]. In practice, this is
most useful for vector types, the X86 backend has [v16i8, v8i16, v4i32,
v2i64, v4f32, v2f64].
Understood. How about the attached patch to clarify this in comment?
- Volodya
Target_regclass.diff (793 Bytes)