reflect: test GC bits for slices

Currently we test bitmap repetitions constructed by the compiler (for
small arrays) and repetitions performed by GC programs (large arrays
and reflect-constructed arrays), but we don't test dynamic repetitions
performed by the runtime for slice backing stores. Add tests that
parallel the array tests using slices.

Change-Id: If4425941a33cc5b20178dd819a7371e347e47585
Reviewed-on: https://go-review.googlesource.com/11422
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index 83952b42dfa0c5d024ad9b8d9cc4e19fab6bb860..1b446797da13ef09a292b7e11c1dc8c4c8b62f0c 100644 (file)
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -4536,6 +4536,25 @@ func verifyGCBits(t *testing.T, typ Type, bits []byte) {
        }
 }
 
+func verifyGCBitsSlice(t *testing.T, typ Type, cap int, bits []byte) {
+       // Creating a slice causes the runtime to repeat a bitmap,
+       // which exercises a different path from making the compiler
+       // repeat a bitmap for a small array or executing a repeat in
+       // a GC program.
+       val := MakeSlice(typ, 0, cap)
+       data := NewAt(ArrayOf(cap, typ), unsafe.Pointer(val.Pointer()))
+       heapBits := GCBits(data.Interface())
+       // Repeat the bitmap for the slice size, trimming scalars in
+       // the last element.
+       bits = rep(cap, bits)
+       for len(bits) > 2 && bits[len(bits)-1] == 0 {
+               bits = bits[:len(bits)-1]
+       }
+       if !bytes.Equal(heapBits, bits) {
+               t.Errorf("heapBits incorrect for make(%v, 0, %v)\nhave %v\nwant %v", typ, cap, heapBits, bits)
+       }
+}
+
 func TestGCBits(t *testing.T) {
        verifyGCBits(t, TypeOf((*byte)(nil)), []byte{1})
 
@@ -4614,6 +4633,31 @@ func TestGCBits(t *testing.T) {
        verifyGCBits(t, TypeOf([2][10000]Xptrscalar{}), rep(2*10000, lit(1, 0)))
        verifyGCBits(t, ArrayOf(2, ArrayOf(10000, Tptrscalar)), rep(2*10000, lit(1, 0)))
 
+       verifyGCBitsSlice(t, TypeOf([]Xptr{}), 0, empty)
+       verifyGCBitsSlice(t, SliceOf(Tptr), 0, empty)
+       verifyGCBitsSlice(t, TypeOf([]Xptrscalar{}), 1, lit(1))
+       verifyGCBitsSlice(t, SliceOf(Tptrscalar), 1, lit(1))
+       verifyGCBitsSlice(t, TypeOf([]Xscalar{}), 2, lit(0))
+       verifyGCBitsSlice(t, SliceOf(Tscalar), 2, lit(0))
+       verifyGCBitsSlice(t, TypeOf([]Xscalar{}), 10000, lit(0))
+       verifyGCBitsSlice(t, SliceOf(Tscalar), 10000, lit(0))
+       verifyGCBitsSlice(t, TypeOf([]Xptr{}), 2, lit(1))
+       verifyGCBitsSlice(t, SliceOf(Tptr), 2, lit(1))
+       verifyGCBitsSlice(t, TypeOf([]Xptr{}), 10000, lit(1))
+       verifyGCBitsSlice(t, SliceOf(Tptr), 10000, lit(1))
+       verifyGCBitsSlice(t, TypeOf([]Xscalarptr{}), 2, lit(0, 1))
+       verifyGCBitsSlice(t, SliceOf(Tscalarptr), 2, lit(0, 1))
+       verifyGCBitsSlice(t, TypeOf([]Xscalarptr{}), 10000, lit(0, 1))
+       verifyGCBitsSlice(t, SliceOf(Tscalarptr), 10000, lit(0, 1))
+       verifyGCBitsSlice(t, TypeOf([]Xptrscalar{}), 2, lit(1, 0))
+       verifyGCBitsSlice(t, SliceOf(Tptrscalar), 2, lit(1, 0))
+       verifyGCBitsSlice(t, TypeOf([]Xptrscalar{}), 10000, lit(1, 0))
+       verifyGCBitsSlice(t, SliceOf(Tptrscalar), 10000, lit(1, 0))
+       verifyGCBitsSlice(t, TypeOf([][10000]Xptrscalar{}), 1, rep(10000, lit(1, 0)))
+       verifyGCBitsSlice(t, SliceOf(ArrayOf(10000, Tptrscalar)), 1, rep(10000, lit(1, 0)))
+       verifyGCBitsSlice(t, TypeOf([][10000]Xptrscalar{}), 2, rep(10000, lit(1, 0)))
+       verifyGCBitsSlice(t, SliceOf(ArrayOf(10000, Tptrscalar)), 2, rep(10000, lit(1, 0)))
+
        verifyGCBits(t, TypeOf((chan [100]Xscalar)(nil)), lit(1))
        verifyGCBits(t, ChanOf(BothDir, ArrayOf(100, Tscalar)), lit(1))