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compiler: do not emit code for unnamed unused variables

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If variable is unnamed and does not contain function call then it's
treated as unused and code generation may be omitted for it
initialization/declaration.
This commit is contained in:
Anna Shaleva 2022-08-19 14:54:42 +03:00
parent 1dcbdb011a
commit 91b36657d6
8 changed files with 151 additions and 18 deletions
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45
pkg/compiler/vardecl_test.go
View file

@ -3,6 +3,8 @@ package compiler_test
import (
"math/big"
"testing"
"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
)
func TestGenDeclWithMultiRet(t *testing.T) {
@ -29,3 +31,46 @@ func TestGenDeclWithMultiRet(t *testing.T) {
eval(t, src, big.NewInt(3))
})
}
func TestUnderscoreLocalVarDontEmitCode(t *testing.T) {
src := `package foo
type Foo struct { Int int }
func Main() int {
var _ int
var _ = 1
var (
A = 2
_ = A + 3
_, B, _ = 4, 5, 6
_, _, _ = f(A, B) // unused, but has function call, so the code is expected
_, C, _ = f(A, B)
)
var D = 7 // unused but named, so the code is expected
_ = D
var _ = Foo{ Int: 5 }
var fo = Foo{ Int: 3 }
var _ = 1 + A + fo.Int
var _ = fo.GetInt() // unused, but has method call, so the code is expected
return C
}
func f(a, b int) (int, int, int) {
return 8, 9, 10
}
func (fo Foo) GetInt() int {
return fo.Int
}`
eval(t, src, big.NewInt(9), []interface{}{opcode.INITSLOT, []byte{5, 0}}, // local slot for A, B, C, D, fo
opcode.PUSH2, opcode.STLOC0, // store A
opcode.PUSH5, opcode.STLOC1, // store B
opcode.LDLOC0, opcode.LDLOC1, opcode.SWAP, []interface{}{opcode.CALL, []byte{27}}, // evaluate f() first time
opcode.DROP, opcode.DROP, opcode.DROP, // drop all values from f
opcode.LDLOC0, opcode.LDLOC1, opcode.SWAP, []interface{}{opcode.CALL, []byte{19}}, // evaluate f() second time
opcode.DROP, opcode.STLOC2, opcode.DROP, // store C
opcode.PUSH7, opcode.STLOC3, // store D
opcode.LDLOC3, opcode.DROP, // empty assignment
opcode.PUSH3, opcode.PUSH1, opcode.PACKSTRUCT, opcode.STLOC4, // fo decl
opcode.LDLOC4, []interface{}{opcode.CALL, []byte{12}}, opcode.DROP, // fo.GetInt()
opcode.LDLOC2, opcode.RET, // return C
[]interface{}{opcode.INITSLOT, []byte{0, 2}}, opcode.PUSH10, opcode.PUSH9, opcode.PUSH8, opcode.RET, // f
[]interface{}{opcode.INITSLOT, []byte{0, 1}}, opcode.LDARG0, opcode.PUSH0, opcode.PICKITEM, opcode.RET) // (fo Foo) GetInt() int
}