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package compile
import (
"bytes"
"fmt"
"testing"
"go.starlark.net/resolve"
"go.starlark.net/syntax"
)
// TestPlusFolding ensures that the compiler generates optimized code for
// n-ary addition of strings, lists, and tuples.
func TestPlusFolding(t *testing.T) {
isPredeclared := func(name string) bool { return name == "x" }
isUniversal := func(name string) bool { return false }
for i, test := range []struct {
src string // source expression
want string // disassembled code
}{
{
// string folding
`"a" + "b" + "c" + "d"`,
`constant "abcd"; return`,
},
{
// string folding with variable:
`"a" + "b" + x + "c" + "d"`,
`constant "ab"; predeclared x; plus; constant "cd"; plus; return`,
},
{
// list folding
`[1] + [2] + [3]`,
`constant 1; constant 2; constant 3; makelist<3>; return`,
},
{
// list folding with variable
`[1] + [2] + x + [3]`,
`constant 1; constant 2; makelist<2>; ` +
`predeclared x; plus; ` +
`constant 3; makelist<1>; plus; ` +
`return`,
},
{
// tuple folding
`() + (1,) + (2, 3)`,
`constant 1; constant 2; constant 3; maketuple<3>; return`,
},
{
// tuple folding with variable
`() + (1,) + x + (2, 3)`,
`constant 1; maketuple<1>; predeclared x; plus; ` +
`constant 2; constant 3; maketuple<2>; plus; ` +
`return`,
},
} {
expr, err := syntax.ParseExpr("in.star", test.src, 0)
if err != nil {
t.Errorf("#%d: %v", i, err)
continue
}
locals, err := resolve.Expr(expr, isPredeclared, isUniversal)
if err != nil {
t.Errorf("#%d: %v", i, err)
continue
}
got := disassemble(Expr(expr, "<expr>", locals).Toplevel)
if test.want != got {
t.Errorf("expression <<%s>> generated <<%s>>, want <<%s>>",
test.src, got, test.want)
}
}
}
// disassemble is a trivial disassembler tailored to the accumulator test.
func disassemble(f *Funcode) string {
out := new(bytes.Buffer)
code := f.Code
for pc := 0; pc < len(code); {
op := Opcode(code[pc])
pc++
// TODO(adonovan): factor in common with interpreter.
var arg uint32
if op >= OpcodeArgMin {
for s := uint(0); ; s += 7 {
b := code[pc]
pc++
arg |= uint32(b&0x7f) << s
if b < 0x80 {
break
}
}
}
if out.Len() > 0 {
out.WriteString("; ")
}
fmt.Fprintf(out, "%s", op)
if op >= OpcodeArgMin {
switch op {
case CONSTANT:
switch x := f.Prog.Constants[arg].(type) {
case string:
fmt.Fprintf(out, " %q", x)
default:
fmt.Fprintf(out, " %v", x)
}
case LOCAL:
fmt.Fprintf(out, " %s", f.Locals[arg].Name)
case PREDECLARED:
fmt.Fprintf(out, " %s", f.Prog.Names[arg])
default:
fmt.Fprintf(out, "<%d>", arg)
}
}
}
return out.String()
}
|
