> wasm-opt --version
wasm-opt version 117 (version_117)
The input code is:
(import "module" "fn" (func $use_array (param (ref $array_i32))))
(data $data
"\01\00\00\00\02\00\00\00\03\00\00\00\04\00\00\00\05\00\00\00 ")
(type $array_i32 (array (mut i32)))
(memory $memory 1)
(func $*init*
(local $x (ref $array_i32))
(array.copy $array_i32 $array_i32
(local.tee $x
(array.new_data $array_i32 $data (i32.const 0) (i32.const 5)))
(i32.const 1)
(local.get $x)
(i32.const 0)
(i32.const 4)
)
(call $use_array (local.get $x))
(call $use_array
(array.new_data $array_i32 $data (i32.const 0) (i32.const 5)))
)
(export "_start" (func $*init*))
The code creates a wasm-gc array with array.new_data, and performs a self copy on that array. Then it allocates another array with the same initial value via array.new_data. The import $use_array is used for preventing DCE.
After optimizing the above file with the following command line:
wasm-opt \
--enable-gc --enable-bulk-memory --enable-reference-types\
-O array_copy.wat -o array_copy.opt.wat\
-S --new-wat-parser
the generated code is:
(module
(type $array_i32 (array (mut i32)))
(type $1 (func (param (ref $array_i32))))
(type $2 (func))
(import "module" "fn" (func $use_array (type $1) (param (ref $array_i32))))
(data $data "\01\00\00\00\02\00\00\00\03\00\00\00\04\00\00\00\05\00\00\00 ")
(export "_start" (func $*init*))
(func $*init* (type $2) (; has Stack IR ;)
(local $0 (ref $array_i32))
(array.copy $array_i32 $array_i32
(local.tee $0
(array.new_data $array_i32 $data
(i32.const 0)
(i32.const 5)
)
)
(i32.const 1)
(local.get $0)
(i32.const 0)
(i32.const 4)
)
(call $use_array
(local.get $0)
)
(call $use_array
(local.get $0)
)
)
)
Note that the second array is replaced with local.get $0, i.e. the first array. But this is incorrect because the first array is already modified by array.copy.
The input code is:
The code creates a wasm-gc array with
array.new_data, and performs a self copy on that array. Then it allocates another array with the same initial value viaarray.new_data. The import$use_arrayis used for preventing DCE.After optimizing the above file with the following command line:
the generated code is:
Note that the second array is replaced with
local.get $0, i.e. the first array. But this is incorrect because the first array is already modified byarray.copy.