Add fwidth_coarse and fwidth_fine functions (#6941)

Fixes #6940.

Add new Slang fwidth_coarse and fwidth_fine functions, similar to GLSL's fwidthCoarse and fwidthFine.
Move the implementation of the GLSL functions from glsl.meta.slang to hlsl.meta.slang.

Update the existing spirv/fwidth.slang test with the new functions, and add a new hlsl-intrinsic/fragment-derivative.slang test to test HLSL, SPIR-V, and GLSL targets for the new functions.

2 files changed, 128 insertions, 68 deletions

diff --git a/source/slang/glsl.meta.slang b/source/slang/glsl.meta.slang
index 85c8b174c..0ea7d1c89 100644
--- a/source/slang/glsl.meta.slang
+++ b/source/slang/glsl.meta.slang
@@ -8898,23 +8898,7 @@ public vector<float, N> dFdyCoarse(vector<float, N> p)
 [require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
 public float fwidthFine(float p)
 {
-    __requireComputeDerivative();
-    __target_switch
-    {
-    case hlsl:
-    {
-        return abs(ddx_fine(p)) + abs(ddy_fine(p));
-    }
-    case glsl: __intrinsic_asm "fwidthFine($0)";
-    case spirv:
-    {
-        return spirv_asm
-        {
-            OpCapability DerivativeControl;
-            OpFwidthFine $$float result $p;
-        };
-    }
-    }
+    return fwidth_fine(p);
 }
 __generic<let N : int>
 [__NoSideEffect]
@@ -8922,23 +8906,7 @@ __generic<let N : int>
 [require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
 public vector<float, N> fwidthFine(vector<float, N> p)
 {
-    __requireComputeDerivative();
-    __target_switch
-    {
-    case hlsl:
-    {
-        return abs(ddx_fine(p)) + abs(ddy_fine(p));
-    }
-    case glsl: __intrinsic_asm "fwidthFine($0)";
-    case spirv:
-    {
-        return spirv_asm
-        {
-            OpCapability DerivativeControl;
-            OpFwidthFine $$vector<float, N> result $p;
-        };
-    }
-    }
+    return fwidth_fine(p);
 }
 
 [__NoSideEffect]
@@ -8946,23 +8914,7 @@ public vector<float, N> fwidthFine(vector<float, N> p)
 [require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
 public float fwidthCoarse(float p)
 {
-    __requireComputeDerivative();
-    __target_switch
-    {
-    case hlsl:
-    {
-        return abs(ddx_coarse(p)) + abs(ddy_coarse(p));
-    }
-    case glsl: __intrinsic_asm "fwidthCoarse($0)";
-    case spirv:
-    {
-        return spirv_asm
-        {
-            OpCapability DerivativeControl;
-            OpFwidthCoarse $$float result $p;
-        };
-    }
-    }
+    return fwidth_coarse(p);
 }
 __generic<let N : int>
 [__NoSideEffect]
@@ -8970,23 +8922,7 @@ __generic<let N : int>
 [require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
 public vector<float, N> fwidthCoarse(vector<float, N> p)
 {
-    __requireComputeDerivative();
-    __target_switch
-    {
-    case hlsl:
-    {
-        return abs(ddx_coarse(p)) + abs(ddy_coarse(p));
-    }
-    case glsl: __intrinsic_asm "fwidthCoarse($0)";
-    case spirv:
-    {
-        return spirv_asm
-        {
-            OpCapability DerivativeControl;
-            OpFwidthCoarse $$vector<float, N> result $p;
-        };
-    }
-    }
+    return fwidth_coarse(p);
 }
 
 [__NoSideEffect]
diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index 3d83e33c1..0f04006e5 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -9940,6 +9940,130 @@ matrix<T, N, M> fwidth(matrix<T, N, M> x)
     }
 }
 
+/// Texture filter width (coarse).
+/// Calculates the sum abs(ddx_coarse(`p`)) + abs(ddy_coarse(`p`)).
+/// @param p The value to sum x and y partial derivative magnitudes for.
+/// @return The sum of abs(ddx_coarse(`p`)) and abs(ddy_coarse(`p`)).
+/// @remarks For SPIR-V, this function maps to `OpFwidthCoarse`.
+/// @category derivative
+__generic<T : __BuiltinFloatingPointType>
+[__readNone]
+[require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
+T fwidth_coarse(T p)
+{
+    __requireComputeDerivative();
+    __target_switch
+    {
+    case hlsl:
+        __intrinsic_asm "abs(ddx_coarse($0)) + abs(ddy_coarse($0))";
+    case glsl:
+        __intrinsic_asm "fwidthCoarse($0)";
+    case spirv:
+        return spirv_asm
+        {
+            OpCapability DerivativeControl;
+            OpFwidthCoarse $$T result $p;
+        };
+    }
+}
+
+__generic<T : __BuiltinFloatingPointType, let N : int>
+[__readNone]
+[require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
+vector<T, N> fwidth_coarse(vector<T, N> x)
+{
+    __requireComputeDerivative();
+    __target_switch
+    {
+    case hlsl:
+        __intrinsic_asm "abs(ddx_coarse($0)) + abs(ddy_coarse($0))";
+    case glsl:
+        __intrinsic_asm "fwidthCoarse($0)";
+    case spirv:
+        return spirv_asm
+        {
+            OpCapability DerivativeControl;
+            OpFwidthCoarse $$vector<T, N> result $x;
+        };
+    }
+}
+
+__generic<T : __BuiltinFloatingPointType, let N : int, let M : int>
+[__readNone]
+[require(glsl_hlsl_spirv, fragmentprocessing)]
+matrix<T, N, M> fwidth_coarse(matrix<T, N, M> x)
+{
+    __target_switch
+    {
+    case hlsl:
+        __intrinsic_asm "abs(ddx_coarse($0)) + abs(ddy_coarse($0))";
+    default:
+        MATRIX_MAP_UNARY(T, N, M, fwidth_coarse, x);
+    }
+}
+
+/// Texture filter width (fine).
+/// Calculates the sum abs(ddx_fine(`p`)) + abs(ddy_fine(`p`)).
+/// @param p The value to sum x and y partial derivative magnitudes for.
+/// @return The sum of abs(ddx_fine(`p`)) and abs(ddy_fine(`p`)).
+/// @remarks For SPIR-V, this function maps to `OpFwidthFine`.
+/// @category derivative
+__generic<T : __BuiltinFloatingPointType>
+[__readNone]
+[require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
+T fwidth_fine(T p)
+{
+    __requireComputeDerivative();
+    __target_switch
+    {
+    case hlsl:
+        __intrinsic_asm "abs(ddx_fine($0)) + abs(ddy_fine($0))";
+    case glsl:
+        __intrinsic_asm "fwidthFine($0)";
+    case spirv:
+        return spirv_asm
+        {
+            OpCapability DerivativeControl;
+            OpFwidthFine $$T result $p;
+        };
+    }
+}
+
+__generic<T : __BuiltinFloatingPointType, let N : int>
+[__readNone]
+[require(glsl_hlsl_spirv, fragmentprocessing_derivativecontrol)]
+vector<T, N> fwidth_fine(vector<T, N> x)
+{
+    __requireComputeDerivative();
+    __target_switch
+    {
+    case hlsl:
+        __intrinsic_asm "abs(ddx_fine($0)) + abs(ddy_fine($0))";
+    case glsl:
+        __intrinsic_asm "fwidthFine($0)";
+    case spirv:
+        return spirv_asm
+        {
+            OpCapability DerivativeControl;
+            OpFwidthFine $$vector<T, N> result $x;
+        };
+    }
+}
+
+__generic<T : __BuiltinFloatingPointType, let N : int, let M : int>
+[__readNone]
+[require(glsl_hlsl_spirv, fragmentprocessing)]
+matrix<T, N, M> fwidth_fine(matrix<T, N, M> x)
+{
+    __target_switch
+    {
+    case hlsl:
+        __intrinsic_asm "abs(ddx_fine($0)) + abs(ddy_fine($0))";
+    default:
+        MATRIX_MAP_UNARY(T, N, M, fwidth_fine, x);
+    }
+}
+
 __intrinsic_op($(kIROp_ResolveVaryingInputRef))
 Ref<T> __ResolveVaryingInputRef<T>(__constref T attribute);