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#define ANNOTATE(property) __attribute__((tag(property)))
struct Cell { int f; } ANNOTATE("GC Thing");
struct RootedCell { RootedCell(Cell*) {} } ANNOTATE("Rooted Pointer");
class AutoSuppressGC_Base {
public:
AutoSuppressGC_Base() {}
~AutoSuppressGC_Base() {}
} ANNOTATE("Suppress GC");
class AutoSuppressGC_Child : public AutoSuppressGC_Base {
public:
AutoSuppressGC_Child() : AutoSuppressGC_Base() {}
};
class AutoSuppressGC {
AutoSuppressGC_Child helpImBeingSuppressed;
public:
AutoSuppressGC() {}
};
extern void GC() ANNOTATE("GC Call");
extern void invisible();
void GC()
{
// If the implementation is too trivial, the function body won't be emitted at all.
asm("");
invisible();
}
extern void usecell(Cell*);
void suppressedFunction() {
GC(); // Calls GC, but is always called within AutoSuppressGC
}
void halfSuppressedFunction() {
GC(); // Calls GC, but is sometimes called within AutoSuppressGC
}
void unsuppressedFunction() {
GC(); // Calls GC, never within AutoSuppressGC
}
volatile static int x = 3;
volatile static int* xp = &x;
struct GCInDestructor {
~GCInDestructor() {
invisible();
asm("");
*xp = 4;
GC();
}
};
Cell*
f()
{
GCInDestructor kaboom;
Cell cell;
Cell* cell1 = &cell;
Cell* cell2 = &cell;
Cell* cell3 = &cell;
Cell* cell4 = &cell;
{
AutoSuppressGC nogc;
suppressedFunction();
halfSuppressedFunction();
}
usecell(cell1);
halfSuppressedFunction();
usecell(cell2);
unsuppressedFunction();
{
// Old bug: it would look from the first AutoSuppressGC constructor it
// found to the last destructor. This statement *should* have no effect.
AutoSuppressGC nogc;
}
usecell(cell3);
Cell* cell5 = &cell;
usecell(cell5);
// Hazard in return value due to ~GCInDestructor
Cell* cell6 = &cell;
return cell6;
}
Cell* copy_and_gc(Cell* src)
{
GC();
return reinterpret_cast<Cell*>(88);
}
void use(Cell* cell)
{
static int x = 0;
if (cell)
x++;
}
struct CellContainer {
Cell* cell;
CellContainer() {
asm("");
}
};
void loopy()
{
Cell cell;
// No hazard: haz1 is not live during call to copy_and_gc.
Cell* haz1;
for (int i = 0; i < 10; i++) {
haz1 = copy_and_gc(haz1);
}
// No hazard: haz2 is live up to just before the GC, and starting at the
// next statement after it, but not across the GC.
Cell* haz2 = &cell;
for (int j = 0; j < 10; j++) {
use(haz2);
GC();
haz2 = &cell;
}
// Hazard: haz3 is live from the final statement in one iteration, across
// the GC in the next, to the use in the 2nd statement.
Cell* haz3;
for (int k = 0; k < 10; k++) {
GC();
use(haz3);
haz3 = &cell;
}
// Hazard: haz4 is live across a GC hidden in a loop.
Cell* haz4 = &cell;
for (int i2 = 0; i2 < 10; i2++) {
GC();
}
use(haz4);
// Hazard: haz5 is live from within a loop across a GC.
Cell* haz5;
for (int i3 = 0; i3 < 10; i3++) {
haz5 = &cell;
}
GC();
use(haz5);
// No hazard: similar to the haz3 case, but verifying that we do not get
// into an infinite loop.
Cell* haz6;
for (int i4 = 0; i4 < 10; i4++) {
GC();
haz6 = &cell;
}
// No hazard: haz7 is constructed within the body, so it can't make a
// hazard across iterations. Note that this requires CellContainer to have
// a constructor, because otherwise the analysis doesn't see where
// variables are declared. (With the constructor, it knows that
// construction of haz7 obliterates any previous value it might have had.
// Not that that's possible given its scope, but the analysis doesn't get
// that information.)
for (int i5 = 0; i5 < 10; i5++) {
GC();
CellContainer haz7;
use(haz7.cell);
haz7.cell = &cell;
}
// Hazard: make sure we *can* see hazards across iterations involving
// CellContainer;
CellContainer haz8;
for (int i6 = 0; i6 < 10; i6++) {
GC();
use(haz8.cell);
haz8.cell = &cell;
}
}
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