tools: Expand / clean-up the template WGSL type helpers

Fix `IsAbstract()` so that it doesn't consider most-nested element types.
Add `ElementType()` and `DeepestElementType()` helpers.
Add `OverloadUsesF16` as a helper for https://dawn-review.googlesource.com/c/dawn/+/96722.

Simplifies template code.

Change-Id: Iff5a9a7258caea06e00ee37c29e5298d9c35b799
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/97361
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>

tools/src/cmd/gen/main.go

@@ -302,8 +302,11 @@ func (g *generator) bindAndParse(t *template.Template, text string) error {
 		"IsTemplateNumberParam": is(sem.TemplateNumberParam{}),
 		"IsTemplateTypeParam":   is(sem.TemplateTypeParam{}),
 		"IsType":                is(sem.Type{}),
+		"ElementType":           gen.ElementType,
+		"DeepestElementType":    gen.DeepestElementType,
 		"IsAbstract":            gen.IsAbstract,
 		"IsDeclarable":          gen.IsDeclarable,
+		"OverloadUsesF16":       gen.OverloadUsesF16,
 		"IsFirstIn":             isFirstIn,
 		"IsLastIn":              isLastIn,
 		"Sem":                   g.cache.sem,

tools/src/tint/intrinsic/gen/gen.go

@@ -444,16 +444,40 @@ func SplitDisplayName(displayName string) []string {
 	return parts
 }
 
-// IsAbstract returns true if the FullyQualifiedName refers to an abstract
-// numeric type
+// ElementType returns the nested type for type represented by the fully qualified name.
+// If the type is not a composite type, then the fully qualified name is returned
+func ElementType(fqn sem.FullyQualifiedName) sem.FullyQualifiedName {
+	switch fqn.Target.GetName() {
+	case "vec":
+		return fqn.TemplateArguments[1].(sem.FullyQualifiedName)
+	case "mat":
+		return fqn.TemplateArguments[2].(sem.FullyQualifiedName)
+	case "array":
+		return fqn.TemplateArguments[0].(sem.FullyQualifiedName)
+	}
+	return fqn
+}
+
+// DeepestElementType returns the inner most nested type for type represented by the
+// fully qualified name.
+func DeepestElementType(fqn sem.FullyQualifiedName) sem.FullyQualifiedName {
+	switch fqn.Target.GetName() {
+	case "vec":
+		return fqn.TemplateArguments[1].(sem.FullyQualifiedName)
+	case "mat":
+		return DeepestElementType(fqn.TemplateArguments[2].(sem.FullyQualifiedName))
+	case "array":
+		return DeepestElementType(fqn.TemplateArguments[0].(sem.FullyQualifiedName))
+	}
+	return fqn
+}
+
+// IsAbstract returns true if the FullyQualifiedName refers to an abstract numeric type float.
+// Use DeepestElementType if you want to include vector, matrices and arrays of abstract types.
 func IsAbstract(fqn sem.FullyQualifiedName) bool {
 	switch fqn.Target.GetName() {
 	case "ia", "fa":
 		return true
-	case "vec":
-		return IsAbstract(fqn.TemplateArguments[1].(sem.FullyQualifiedName))
-	case "mat":
-		return IsAbstract(fqn.TemplateArguments[2].(sem.FullyQualifiedName))
 	}
 	return false
 }
@@ -461,5 +485,20 @@ func IsAbstract(fqn sem.FullyQualifiedName) bool {
 // IsDeclarable returns false if the FullyQualifiedName refers to an abstract
 // numeric type, or if it starts with a leading underscore.
 func IsDeclarable(fqn sem.FullyQualifiedName) bool {
-	return !IsAbstract(fqn) && !strings.HasPrefix(fqn.Target.GetName(), "_")
+	return !IsAbstract(DeepestElementType(fqn)) && !strings.HasPrefix(fqn.Target.GetName(), "_")
+}
+
+// OverloadUsesF16 returns true if the overload uses the f16 type anywhere in the signature.
+func OverloadUsesF16(overload *sem.Overload, typename string) bool {
+	for _, param := range overload.Parameters {
+		if DeepestElementType(param.Type).Target.GetName() == "f16" {
+			return true
+		}
+	}
+	if ret := overload.ReturnType; ret != nil {
+		if DeepestElementType(*overload.ReturnType).Target.GetName() == "f16" {
+			return true
+		}
+	}
+	return false
 }

tools/src/tint/intrinsic/gen/permutate.go

@@ -336,8 +336,8 @@ func validate(fqn sem.FullyQualifiedName, uses *sem.StageUses) bool {
 			strings.Contains(elTyName, "sampler"),
 			strings.Contains(elTyName, "texture"):
 			return false // Not storable
-		case IsAbstract(elTy):
-			return false // Abstract types are not typeable nor supported by arrays
+		case IsAbstract(DeepestElementType(elTy)):
+			return false // Abstract types are not typeable
 		}
 	case "ptr":
 		// https://gpuweb.github.io/gpuweb/wgsl/#storage-class