[docs][WebAssembly] WebAssembly-specific release notes for 10.0.

Author: sunfishcode

clang/docs/ReleaseNotes.rst

@@ -119,6 +119,9 @@ Non-comprehensive list of changes in this release
 * Improved support for ``octeon`` MIPS-family CPU. Added ``octeon+`` to
   the list of of CPUs accepted by the driver.
 
+* For the WebAssembly target, the ``wasm-opt`` tool will now be run if it is
+  found in the PATH, which can reduce code size.
+
 New Compiler Flags
 ------------------
 

lld/docs/ReleaseNotes.rst

@@ -86,3 +86,4 @@ WebAssembly Improvements
   as it's best to keep them internal when possible. They can be
   explicitly exported with `--export=__data_end` and
   `--export=__heap_base`, respectively.
+* wasm-ld now elides .bss sections when the memory is not imported

llvm/docs/ReleaseNotes.rst

@@ -234,7 +234,12 @@ Changes to the AVR Target
 Changes to the WebAssembly Target
 ---------------------------------
 
- During this release ...
+* __attribute__((used)) no longer implies that a symbol is exported, for
+  consistency with other targets.
+* Multivalue function signatures are now supported in WebAssembly object files
+* The new `atomic.fence` instruction is now supported
+* Thread-Local Storage (TLS) is now supported.
+* SIMD support is significantly expanded.
 
 Changes to the Windows Target
 -----------------------------