[WGSL] Bitcast needs to concretize abstract floats

https://bugs.webkit.org/show_bug.cgi?id=268380
rdar://121527210

Reviewed by Mike Wyrzykowski.

Bitcast doesn't concretize its arguments by default, since there's a special case
for conversions from abstract int to u32, so we need to explicitly concretize
abstract floats.

* Source/WebGPU/WGSL/ConstantFunctions.h:
(WGSL::CONSTANT_FUNCTION):
* Source/WebGPU/WGSL/tests/valid/overload.wgsl:

Canonical link: https://commits.webkit.org/273764@main

Source/WebGPU/WGSL/ConstantFunctions.h

@@ -1718,6 +1718,14 @@ CONSTANT_FUNCTION(Bitcast)
             return makeUnexpected(makeString("value ", String::number(*abstractInt), " cannot be represented as 'i32'"));
         return { convertValue<BitwiseCast>(resultType, *result) };
     }
+
+    if (auto* abstractFloat = std::get_if<double>(&argument)) {
+        auto result = convertFloat<float>(*abstractFloat);
+        if (!result.has_value())
+            return makeUnexpected(makeString("value ", String::number(*abstractFloat), " cannot be represented as 'f32'"));
+        return { convertValue<BitwiseCast>(resultType, *result) };
+    }
+
     return { convertValue<BitwiseCast>(resultType, argument) };
 }
 

Source/WebGPU/WGSL/tests/valid/overload.wgsl

@@ -1355,6 +1355,8 @@ fn testBitcast()
     let f = 0f;
     let h = 0h;
 
+    { const x =bitcast<vec2<i32>>(vec2(.659341217228384203)); }
+
     // @const @must_use fn bitcast<T>(e : T) -> T
     { const x: u32 = bitcast<u32>(5u); }
     { const x: i32 = bitcast<i32>(5i); }