threads: add global.atomic.rmw.* instructions (#1563)

* threads: add `global.atomic.rmw.*` instructions

This change adds support for the various `global.atomic.rmw.*`
instructions that are now available as a part of the
shared-everything-threads [proposal].

[proposal]: https://github.com/WebAssembly/shared-everything-threads

* Fix operand validation; refactor validation helpers

The `global.atomic.rmw.*` instructions have different validation
constraints for different instructions. `xchg` maches
`global.atomic.get|set` in that it accepts subtypes of `anyref`. But
`cmpxchg` accepts subtypes of `eqref`. All the instructions accept `i32`
and `i64`. To make this more clear (and avoid mistakes like the ones I
made), I moved these "special" cases up a level to be more visible. This
allowed removing some of the other helper functions.

Author: abrown

crates/wasm-encoder/src/core/code.rs

@@ -1020,6 +1020,34 @@ pub enum Instruction<'a> {
         ordering: Ordering,
         global_index: u32,
     },
+    GlobalAtomicRmwAdd {
+        ordering: Ordering,
+        global_index: u32,
+    },
+    GlobalAtomicRmwSub {
+        ordering: Ordering,
+        global_index: u32,
+    },
+    GlobalAtomicRmwAnd {
+        ordering: Ordering,
+        global_index: u32,
+    },
+    GlobalAtomicRmwOr {
+        ordering: Ordering,
+        global_index: u32,
+    },
+    GlobalAtomicRmwXor {
+        ordering: Ordering,
+        global_index: u32,
+    },
+    GlobalAtomicRmwXchg {
+        ordering: Ordering,
+        global_index: u32,
+    },
+    GlobalAtomicRmwCmpxchg {
+        ordering: Ordering,
+        global_index: u32,
+    },
 }
 
 impl Encode for Instruction<'_> {
@@ -3183,6 +3211,69 @@ impl Encode for Instruction<'_> {
                 ordering.encode(sink);
                 global_index.encode(sink);
             }
+            Instruction::GlobalAtomicRmwAdd {
+                ordering,
+                global_index,
+            } => {
+                sink.push(0xFE);
+                sink.push(0x51);
+                ordering.encode(sink);
+                global_index.encode(sink);
+            }
+            Instruction::GlobalAtomicRmwSub {
+                ordering,
+                global_index,
+            } => {
+                sink.push(0xFE);
+                sink.push(0x52);
+                ordering.encode(sink);
+                global_index.encode(sink);
+            }
+            Instruction::GlobalAtomicRmwAnd {
+                ordering,
+                global_index,
+            } => {
+                sink.push(0xFE);
+                sink.push(0x53);
+                ordering.encode(sink);
+                global_index.encode(sink);
+            }
+            Instruction::GlobalAtomicRmwOr {
+                ordering,
+                global_index,
+            } => {
+                sink.push(0xFE);
+                sink.push(0x54);
+                ordering.encode(sink);
+                global_index.encode(sink);
+            }
+            Instruction::GlobalAtomicRmwXor {
+                ordering,
+                global_index,
+            } => {
+                sink.push(0xFE);
+                sink.push(0x55);
+                ordering.encode(sink);
+                global_index.encode(sink);
+            }
+            Instruction::GlobalAtomicRmwXchg {
+                ordering,
+                global_index,
+            } => {
+                sink.push(0xFE);
+                sink.push(0x56);
+                ordering.encode(sink);
+                global_index.encode(sink);
+            }
+            Instruction::GlobalAtomicRmwCmpxchg {
+                ordering,
+                global_index,
+            } => {
+                sink.push(0xFE);
+                sink.push(0x57);
+                ordering.encode(sink);
+                global_index.encode(sink);
+            }
         }
     }
 }

crates/wasmparser/src/binary_reader.rs

@@ -1684,6 +1684,25 @@ impl<'a> BinaryReader<'a> {
             // Decode shared-everything-threads proposal.
             0x4f => visitor.visit_global_atomic_get(self.read_ordering()?, self.read_var_u32()?),
             0x50 => visitor.visit_global_atomic_set(self.read_ordering()?, self.read_var_u32()?),
+            0x51 => {
+                visitor.visit_global_atomic_rmw_add(self.read_ordering()?, self.read_var_u32()?)
+            }
+            0x52 => {
+                visitor.visit_global_atomic_rmw_sub(self.read_ordering()?, self.read_var_u32()?)
+            }
+            0x53 => {
+                visitor.visit_global_atomic_rmw_and(self.read_ordering()?, self.read_var_u32()?)
+            }
+            0x54 => visitor.visit_global_atomic_rmw_or(self.read_ordering()?, self.read_var_u32()?),
+            0x55 => {
+                visitor.visit_global_atomic_rmw_xor(self.read_ordering()?, self.read_var_u32()?)
+            }
+            0x56 => {
+                visitor.visit_global_atomic_rmw_xchg(self.read_ordering()?, self.read_var_u32()?)
+            }
+            0x57 => {
+                visitor.visit_global_atomic_rmw_cmpxchg(self.read_ordering()?, self.read_var_u32()?)
+            }
 
             _ => bail!(pos, "unknown 0xfe subopcode: 0x{code:x}"),
         })

crates/wasmparser/src/lib.rs

@@ -498,6 +498,13 @@ macro_rules! for_each_operator {
             // https://github.com/WebAssembly/shared-everything-threads
             @shared_everything_threads GlobalAtomicGet { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_get
             @shared_everything_threads GlobalAtomicSet { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_set
+            @shared_everything_threads GlobalAtomicRmwAdd { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_rmw_add
+            @shared_everything_threads GlobalAtomicRmwSub { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_rmw_sub
+            @shared_everything_threads GlobalAtomicRmwAnd { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_rmw_and
+            @shared_everything_threads GlobalAtomicRmwOr { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_rmw_or
+            @shared_everything_threads GlobalAtomicRmwXor { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_rmw_xor
+            @shared_everything_threads GlobalAtomicRmwXchg { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_rmw_xchg
+            @shared_everything_threads GlobalAtomicRmwCmpxchg { ordering: $crate::Ordering, global_index: u32 } => visit_global_atomic_rmw_cmpxchg
 
             // 0xFD operators
             // 128-bit SIMD