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runtime: rewrite lfstack packing/unpacking to look more like that in Go

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Reviewed-on: https://go-review.googlesource.com/13037

From-SVN: r228057
This commit is contained in:
Ian Lance Taylor 2015-09-23 17:07:15 +00:00
parent a9c238108b
commit 46efdbbc01
2 changed files with 38 additions and 22 deletions
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2
gcc/go/gofrontend/MERGE
View file

@ -1,4 +1,4 @@
e069d4417a692c1261df99fe3323277e1a0193d2
2087b95180caea3477647c449772b7fecc01a71c
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.

58
libgo/runtime/lfstack.goc
View file

@ -9,25 +9,41 @@ package runtime
#include "arch.h"
#if __SIZEOF_POINTER__ == 8
// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
// So we use 17msb of pointers as ABA counter.
# define PTR_BITS 47
#else
# define PTR_BITS 32
#endif
#define PTR_MASK ((1ull<<PTR_BITS)-1)
#define CNT_MASK (0ull-1)
#if __SIZEOF_POINTER__ == 8 && (defined(__sparc__) || (defined(__sun__) && defined(__amd64__)))
// SPARC64 and Solaris on AMD64 uses all 64 bits of virtual addresses.
// Use low-order three bits as ABA counter.
// http://docs.oracle.com/cd/E19120-01/open.solaris/816-5138/6mba6ua5p/index.html
#undef PTR_BITS
#undef CNT_MASK
#undef PTR_MASK
#define PTR_BITS 0
#define CNT_MASK 7
#define PTR_MASK ((0ull-1)<<3)
# if defined(__sparc__) || (defined(__sun__) && defined(__amd64__))
static inline uint64 lfPack(LFNode *node, uintptr cnt) {
return ((uint64)(node)) | ((cnt)&7);
}
static inline LFNode* lfUnpack(uint64 val) {
return (LFNode*)(val&~7);
}
# else
# if defined(__aarch64__)
// Depending on the kernel options, pointers on arm64 can have up to 48 significant
// bits (see https://www.kernel.org/doc/Documentation/arm64/memory.txt).
# define PTR_BITS 48
# else
// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
// So we use 17msb of pointers as ABA counter.
# define PTR_BITS 47
# endif
# endif
# define CNT_BITS (64 - PTR_BITS + 3)
static inline uint64 lfPack(LFNode *node, uintptr cnt) {
return ((uint64)(node)<<(64-PTR_BITS)) | (cnt&(((1<<CNT_BITS)-1)));
}
static inline LFNode* lfUnpack(uint64 val) {
return (LFNode*)((val >> CNT_BITS) << 3);
}
#else
static inline uint64 lfPack(LFNode *node, uintptr cnt) {
return ((uint64)(uintptr)(node)<<32) | cnt;
}
static inline LFNode* lfUnpack(uint64 val) {
return (LFNode*)(uintptr)(val >> 32);
}
#endif
void
@ -35,16 +51,16 @@ runtime_lfstackpush(uint64 *head, LFNode *node)
{
uint64 old, new;
if((uintptr)node != ((uintptr)node&PTR_MASK)) {
if(node != lfUnpack(lfPack(node, 0))) {
runtime_printf("p=%p\n", node);
runtime_throw("runtime_lfstackpush: invalid pointer");
}
node->pushcnt++;
new = (uint64)(uintptr)node|(((uint64)node->pushcnt&CNT_MASK)<<PTR_BITS);
new = lfPack(node, node->pushcnt);
for(;;) {
old = runtime_atomicload64(head);
node->next = (LFNode*)(uintptr)(old&PTR_MASK);
node->next = lfUnpack(old);
if(runtime_cas64(head, old, new))
break;
}
@ -60,11 +76,11 @@ runtime_lfstackpop(uint64 *head)
old = runtime_atomicload64(head);
if(old == 0)
return nil;
node = (LFNode*)(uintptr)(old&PTR_MASK);
node = lfUnpack(old);
node2 = runtime_atomicloadp(&node->next);
new = 0;
if(node2 != nil)
new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt&CNT_MASK)<<PTR_BITS);
new = lfPack(node2, node2->pushcnt);
if(runtime_cas64(head, old, new))
return node;
}