[CIR][CIRGen][Builtin][X86] Lower xsave related intrinsics

[RiverDave]

Two things:

1. Added some NYI placeholders
2. Tests for i386(x86) are pending as we haven't dealt with that triple yet as compared to CG.

[github-actions]

⚠️ undef deprecator found issues in your code. ⚠️

You can test this locally with the following command:

git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef[^a-zA-Z0-9_-]|UndefValue::get)' 4820d600ed3362744372983068495f086c9a0659 2fae69746794a169685714e426f9f2c7bf343832 clang/test/CIR/CodeGen/X86/x86_64-xsave.c clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp

The following files introduce new uses of undef:

• clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp

Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields undef. You should use poison values for placeholders instead.

In tests, avoid using undef and having tests that trigger undefined behavior. If you need an operand with some unimportant value, you can add a new argument to the function and use that instead.

For example, this is considered a bad practice:

define void @fn() {
  ...
  br i1 undef, ...
}

Please use the following instead:

define void @fn(i1 %cond) {
  ...
  br i1 %cond, ...
}

Please refer to the Undefined Behavior Manual for more information.

[RiverDave]

⚠️ undef deprecator found issues in your code. ⚠️

You can test this locally with the following command:
The following files introduce new uses of undef:

• clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp

Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields undef. You should use poison values for placeholders instead.

In tests, avoid using undef and having tests that trigger undefined behavior. If you need an operand with some unimportant value, you can add a new argument to the function and use that instead.

For example, this is considered a bad practice:

define void @fn() {
  ...
  br i1 undef, ...
}

Please use the following instead:

define void @fn(i1 %cond) {
  ...
  br i1 %cond, ...
}

Please refer to the Undefined Behavior Manual for more information.

Do we want parity with CG for these undef intrinsics given this deprecation?

[bcardosolopes]

Do we want parity with CG for these undef intrinsics given this deprecation?

Yep, for this specific instance we are better off ignoring the message (the intrinsics are still there in OG).