Commit `2c2bc9c8df`

Luuk de Gram <luuk@degram.dev>

2023-11-01 19:43:03

wasm: fix bitcasting to -and from arrays

Arrays are currently always passed by reference, this means that we always keep the value in linear memory and never load it to Wasm's stack. Scalar values however do get lowered to Wasm's stack. This means when bitcasting from an array to a scalar value, we must load the memory of the array as such scalar type. To bitcast a scalar type to an array, we allocate a new temporary in the linear data segment, and then store the scalar value there.

master

1 parent 7c5d01b

Changed files (1)

src

arch

wasm

CodeGen.zig

@@ -3814,6 +3814,16 @@ fn airBitcast(func: *CodeGen, inst: Air.Inst.Index) InnerError!void {
             const bitcast_result = try func.bitcast(wanted_ty, given_ty, operand);
             break :result try bitcast_result.toLocal(func, wanted_ty);
         }
+        const mod = func.bin_file.base.options.module.?;
+        if (isByRef(given_ty, mod) and !isByRef(wanted_ty, mod)) {
+            const loaded_memory = try func.load(operand, wanted_ty, 0);
+            break :result try loaded_memory.toLocal(func, wanted_ty);
+        }
+        if (!isByRef(given_ty, mod) and isByRef(wanted_ty, mod)) {
+            const stack_memory = try func.allocStack(wanted_ty);
+            try func.store(stack_memory, operand, given_ty, 0);
+            break :result stack_memory;
+        }
         break :result func.reuseOperand(ty_op.operand, operand);
     };
     func.finishAir(inst, result, &.{ty_op.operand});

Commit 2c2bc9c8df

Commit `2c2bc9c8df`