Initial `Atomic<T>` type implementation. (#5125)

* Initial Atomic<T> type implementation.

* Update design doc.

* Fix.

* Add test.

* Fixes and add tests.

* Fix WGSL.

* Fix glsl.

* Fix metal.

* experiemnt with github metal.

* experiment github metal 2

* github metal experiment 3

* experiment with github metal 4.

* experiment with metal 5.

* experiment 7.

* metal experiment 8.

* Fix metal tests.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 58 insertions, 28 deletions

diff --git a/docs/proposals/003-atomic-t.md b/docs/proposals/003-atomic-t.md
index 03df9bb5e..d05067714 100644
--- a/docs/proposals/003-atomic-t.md
+++ b/docs/proposals/003-atomic-t.md
@@ -7,11 +7,11 @@ Status
 
 Author: Yong He
 
-Status: Design Discussion.
+Status: Implementation in review.
 
-Implementation: N/A
+Implementation: [PR 5125](https://github.com/shader-slang/slang/pull/5125)
 
-Reviewed by: N/A
+Reviewed by: Theresa Foley, Jay Kwak
 
 Background
 ----------
@@ -31,42 +31,72 @@ Proposed Approach
 -----------------
 
 We define an `Atomic<T>` type that functions as a wrapper of `T` and provides atomic operations:
-```
-[sealed] interface IAtomicable {}
-[sealed] interface IArithmeticAtomicable : IAtomicable {}
-[sealed] interface IBitAtomicable : IArithmeticAtomicable {}
+```csharp
+enum MemoryOrder
+{
+    Relaxed = 0,
+    Acquire = 1,
+    Release = 2,
+    AcquireRelease = 3,
+    SeqCst = 4,
+}
 
-extension int : IArithmeticAtomicable {}
-extension uint : IArithmeticAtomicable {}
-extension int64_t : IBitAtomicable {}
-extension uint64_t : IBitAtomicable {}
-extension float : IArithmeticAtomicable {}
-extension half : IArithmeticAtomicable {}
+[sealed] interface IAtomicable {}
+[sealed] interface IArithmeticAtomicable : IAtomicable, IArithmetic {}
+[sealed] interface IBitAtomicable : IArithmeticAtomicable, IInteger {}
 
+[require(cuda_glsl_hlsl_metal_spirv_wgsl)]
 struct Atomic<T : IAtomicable>
 {
-    T load();
-    [ref] void store(T newValue); // Question: do we really need this?
-    [ref] T exchange(T newValue); // returns old value
-    [ref] T compareExchange(T compareValue, T newValue); // returns old value.
+    T load(MemoryOrder order = MemoryOrder.Relaxed);
+
+    [__ref] void store(T newValue, MemoryOrder order = MemoryOrder.Relaxed);
+
+    [__ref] T exchange(T newValue, MemoryOrder order = MemoryOrder.Relaxed); // returns old value
+
+    [__ref] T compareExchange(
+        T compareValue,
+        T newValue,
+        MemoryOrder successOrder = MemoryOrder.Relaxed,
+        MemoryOrder failOrder = MemoryOrder.Relaxed);
 }
 
-extension<T:IArithmeticAtomicable> Atomic<T>
+extension<T : IArithmeticAtomicable> Atomic<T>
 {
-    [ref] T atomicAdd(T value); // returns original value
-    [ref] T atomicSub(T value); // returns original value
-    [ref] T atomicMax(T value); // returns original value
-    [ref] T atomicMin(T value); // returns original value
-    [ref] T atomicIncrement();
-    [ref] T atomicDecrement();
+    [__ref] T add(T value, MemoryOrder order = MemoryOrder.Relaxed); // returns original value
+    [__ref] T sub(T value, MemoryOrder order = MemoryOrder.Relaxed); // returns original value
+    [__ref] T max(T value, MemoryOrder order = MemoryOrder.Relaxed); // returns original value
+    [__ref] T min(T value, MemoryOrder order = MemoryOrder.Relaxed); // returns original value
 }
 
-extension<T:IBitAtomicable> Atomic<T>
+extension<T : IBitAtomicable> Atomic<T>
 {
-    [ref] T atomicAnd(T value); // returns original value
-    [ref] T atomicOr(T value); // returns original value
-    [ref] T atomicXor(T value); // returns original value
+    [__ref] T and(T value, MemoryOrder order = MemoryOrder.Relaxed); // returns original value
+    [__ref] T or(T value, MemoryOrder order = MemoryOrder.Relaxed);  // returns original value
+    [__ref] T xor(T value, MemoryOrder order = MemoryOrder.Relaxed); // returns original value
+    [__ref] T increment(MemoryOrder order = MemoryOrder.Relaxed); // returns original value
+    [__ref] T decrement(MemoryOrder order = MemoryOrder.Relaxed); // returns original value
 }
+
+extension int : IArithmeticAtomicable {}
+extension uint : IArithmeticAtomicable {}
+extension int64_t : IBitAtomicable {}
+extension uint64_t : IBitAtomicable {}
+extension double : IArithmeticAtomicable {}
+extension float : IArithmeticAtomicable {}
+extension half : IArithmeticAtomicable {}
+
+// Operator overloads:
+// All operator overloads are using MemoryOrder.Relaxed semantics.
+__prefix T operator++<T>(__ref Atomic<T> v); // returns new value.
+__postfix T operator++<T>(__ref Atomic<T> v); // returns original value.
+__prefix T operator--<T>(__ref Atomic<T> v); // returns new value.
+__postfix T operator--<T>(__ref Atomic<T> v); // returns original value.
+T operator+=(__ref Atomic<T> v, T operand); // returns new value.
+T operator-=(__ref Atomic<T> v, T operand); // returns new value.
+T operator|=(__ref Atomic<T> v, T operand); // returns new value.
+T operator&=(__ref Atomic<T> v, T operand); // returns new value.
+T operator^=(__ref Atomic<T> v, T operand); // returns new value.
 ```
 
 We allow `Atomic<T>` to be defined anywhere: as struct fields, as array elements, as elements of `RWStructuredBuffer` types,