Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC

Commits:

• eaa8093b
  by Cheng Shao at 2025-05-11T03:25:28-04:00

  wasm: mark freeJSVal as INLINE
  
  This patch marks `freeJSVal` as `INLINE` for the wasm backend. I
  noticed that the `freeJSVal` invocations are not inlined when
  inspecting STG/Cmm dumps of downstream libraries that use release
  build of the wasm backend. The performance benefit of inlining here is
  very modest, but so is the cost anyway; if you are using `freeJSVal`
  at all then you care about every potential chance to improve
  performance :)
  

• eac196df
  by Cheng Shao at 2025-05-11T03:25:28-04:00

  wasm: add zero length fast path for fromJSString
  
  This patch adds a zero length fast path for `fromJSString`; when
  marshaling a zero-length `JSString` we don't need to allocate an empty
  `ByteArray#` at all.
  

1 changed file:

• libraries/ghc-internal/src/GHC/Internal/Wasm/Prim/Types.hs

Changes:

 -- the same 'JSVal', subsequent invocations are no-ops. You are

 -- strongly recommended to call 'freeJSVal' on short-lived

 -- intermediate 'JSVal' values for timely release of resources!

+{-# INLINE freeJSVal #-}

 freeJSVal :: JSVal -> IO ()

 freeJSVal v@(JSVal p) = do

   js_callback_unregister v

 -- eagerly once the resulting 'String' is forced, and the argument

 -- 'JSString' may be explicitly freed if no longer used.

 fromJSString :: JSString -> String

-fromJSString s = unsafeDupablePerformIO $ do

-  l <- js_stringLength s

-  fp <- mallocPlainForeignPtrBytes $ l * 3

-  withForeignPtr fp $ \buf -> do

-    l' <- js_encodeInto s buf $ l * 3

-    peekCStringLen utf8 (buf, l')

+fromJSString s = case js_stringLength s * 3 of

+  0 -> ""

+  max_len -> unsafePerformIO $ do

+    fptr <- mallocPlainForeignPtrBytes max_len

+    withForeignPtr fptr $ \ptr -> do

+      len <- js_encodeInto s ptr max_len

+      peekCStringLen utf8 (ptr, len)

 foreign import javascript unsafe "$1.length"

-  js_stringLength :: JSString -> IO Int

+  js_stringLength :: JSString -> Int

 foreign import javascript unsafe "(new TextEncoder()).encodeInto($1, new Uint8Array(__exports.memory.buffer, $2, $3)).written"

   js_encodeInto :: JSString -> Ptr a -> Int -> IO Int