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runtime: remove obsolete afterprologue check 

Afterprologue check was required when did not know
about return arguments of functions and/or they were not zeroed.
Now 100% precision is required for stacks due to stack copying,
so it must work w/o afterprologue one way or another.
I can limit this change for 1.3 to merely adding a TODO,
but this check is super confusing so I don't want this knowledge to get lost.

LGTM=rsc
R=golang-codereviews, gobot, rsc, khr
CC=golang-codereviews, khr, rsc
https://golang.org/cl/96580045
This commit is contained in:
Dmitriy Vyukov 2014-06-19 22:04:10 -07:00
parent 26282e4093
commit cc81712190
1 changed files with 30 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
src/pkg/runtime/mgc0.c
View File

@ -1434,12 +1434,12 @@ runtime·stackmapdata(StackMap *stackmap, int32 n)
// Scans an interface data value when the interface type indicates
// that it is a pointer.
static void
scaninterfacedata(uintptr bits, byte *scanp, bool afterprologue, void *wbufp)
scaninterfacedata(uintptr bits, byte *scanp, void *wbufp)
{
Itab *tab;
Type *type;
if(runtime·precisestack && afterprologue) {
if(runtime·precisestack) {
if(bits == BitsIface) {
tab = *(Itab**)scanp;
if(tab->type->size <= sizeof(void*) && (tab->type->kind & KindNoPointers))
@ -1455,7 +1455,7 @@ scaninterfacedata(uintptr bits, byte *scanp, bool afterprologue, void *wbufp)
// Starting from scanp, scans words corresponding to set bits.
static void
scanbitvector(Func *f, bool precise, byte *scanp, BitVector *bv, bool afterprologue, void *wbufp)
scanbitvector(Func *f, bool precise, byte *scanp, BitVector *bv, void *wbufp)
{
uintptr word, bits;
uint32 *wordp;
@ -1549,7 +1549,7 @@ scanbitvector(Func *f, bool precise, byte *scanp, BitVector *bv, bool afterprolo
else
runtime·printf("frame %s @%p: iface %p %p\n", runtime·funcname(f), p, ((uintptr*)p)[0], ((uintptr*)p)[1]);
}
scaninterfacedata(word & 3, p, afterprologue, wbufp);
scaninterfacedata(word & 3, p, wbufp);
}
break;
}
@ -1570,7 +1570,6 @@ scanframe(Stkframe *frame, void *wbufp)
uintptr size;
uintptr targetpc;
int32 pcdata;
bool afterprologue;
bool precise;
f = frame->fn;
@ -1591,36 +1590,33 @@ scanframe(Stkframe *frame, void *wbufp)
// Scan local variables if stack frame has been allocated.
// Use pointer information if known.
afterprologue = (frame->varp > (byte*)frame->sp);
precise = false;
if(afterprologue) {
stackmap = runtime·funcdata(f, FUNCDATA_LocalsPointerMaps);
if(stackmap == nil) {
// No locals information, scan everything.
size = frame->varp - (byte*)frame->sp;
if(Debug > 2)
runtime·printf("frame %s unsized locals %p+%p\n", runtime·funcname(f), frame->varp-size, size);
enqueue1(wbufp, (Obj){frame->varp - size, size, 0});
} else if(stackmap->n < 0) {
// Locals size information, scan just the locals.
size = -stackmap->n;
if(Debug > 2)
runtime·printf("frame %s conservative locals %p+%p\n", runtime·funcname(f), frame->varp-size, size);
enqueue1(wbufp, (Obj){frame->varp - size, size, 0});
} else if(stackmap->n > 0) {
// Locals bitmap information, scan just the pointers in
// locals.
if(pcdata < 0 || pcdata >= stackmap->n) {
// don't know where we are
runtime·printf("pcdata is %d and %d stack map entries for %s (targetpc=%p)\n",
pcdata, stackmap->n, runtime·funcname(f), targetpc);
runtime·throw("scanframe: bad symbol table");
}
bv = runtime·stackmapdata(stackmap, pcdata);
size = (bv.n * PtrSize) / BitsPerPointer;
precise = true;
scanbitvector(f, true, frame->varp - size, &bv, afterprologue, wbufp);
stackmap = runtime·funcdata(f, FUNCDATA_LocalsPointerMaps);
if(stackmap == nil) {
// No locals information, scan everything.
size = frame->varp - (byte*)frame->sp;
if(Debug > 2)
runtime·printf("frame %s unsized locals %p+%p\n", runtime·funcname(f), frame->varp-size, size);
enqueue1(wbufp, (Obj){frame->varp - size, size, 0});
} else if(stackmap->n < 0) {
// Locals size information, scan just the locals.
size = -stackmap->n;
if(Debug > 2)
runtime·printf("frame %s conservative locals %p+%p\n", runtime·funcname(f), frame->varp-size, size);
enqueue1(wbufp, (Obj){frame->varp - size, size, 0});
} else if(stackmap->n > 0) {
// Locals bitmap information, scan just the pointers in
// locals.
if(pcdata < 0 || pcdata >= stackmap->n) {
// don't know where we are
runtime·printf("pcdata is %d and %d stack map entries for %s (targetpc=%p)\n",
pcdata, stackmap->n, runtime·funcname(f), targetpc);
runtime·throw("scanframe: bad symbol table");
}
bv = runtime·stackmapdata(stackmap, pcdata);
size = (bv.n * PtrSize) / BitsPerPointer;
precise = true;
scanbitvector(f, true, frame->varp - size, &bv, wbufp);
}
// Scan arguments.
@ -1628,7 +1624,7 @@ scanframe(Stkframe *frame, void *wbufp)
stackmap = runtime·funcdata(f, FUNCDATA_ArgsPointerMaps);
if(stackmap != nil) {
bv = runtime·stackmapdata(stackmap, pcdata);
scanbitvector(f, precise, frame->argp, &bv, true, wbufp);
scanbitvector(f, precise, frame->argp, &bv, wbufp);
} else {
if(Debug > 2)
runtime·printf("frame %s conservative args %p+%p\n", runtime·funcname(f), frame->argp, (uintptr)frame->arglen);