wasm: Implement `@wasmMemoryGrow` builtin

Similarly to the other wasm builtin, this implements the grow variation where the memory
index is a comptime known value. The operand as well as the result are runtime values.
This also verifies during semantic analysis the target we're building for is wasm, or else
emits a compilation error. This means that other backends do not have to handle this AIR instruction,
other than the wasm and LLVM backends.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/arch/wasm/CodeGen.zig b/src/arch/wasm/CodeGen.zig
index 0ea0418d7f..b4917738dd 100644
--- a/src/arch/wasm/CodeGen.zig
+++ b/src/arch/wasm/CodeGen.zig
@@ -1672,6 +1672,7 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
         .wrap_errunion_err => self.airWrapErrUnionErr(inst),
 
         .wasm_memory_size => self.airWasmMemorySize(inst),
+        .wasm_memory_grow => self.airWasmMemoryGrow(inst),
 
         .add_sat,
         .sub_sat,
@@ -3438,6 +3439,18 @@ fn airWasmMemorySize(self: *Self, inst: Air.Inst.Index) !WValue {
     return result;
 }
 
+fn airWasmMemoryGrow(self: *Self, inst: Air.Inst.Index) !WValue {
+    const pl_op = self.air.instructions.items(.data)[inst].pl_op;
+    const extra = self.air.extraData(Air.WasmMemoryIndex, pl_op.payload).data;
+    const operand = try self.resolveInst(pl_op.operand);
+
+    const result = try self.allocLocal(Type.usize);
+    try self.emitWValue(operand);
+    try self.addLabel(.memory_grow, extra.index);
+    try self.addLabel(.local_set, result.local);
+    return result;
+}
+
 fn cmpOptionals(self: *Self, lhs: WValue, rhs: WValue, operand_ty: Type, op: std.math.CompareOperator) InnerError!WValue {
     assert(operand_ty.hasRuntimeBits());
     assert(op == .eq or op == .neq);