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Fix #17121 - cache profiler symbol lookups #23291

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Fix #17121 - cache profiler symbol lookups #23291

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2bc5ea6
Fix #17121 - cache profiler symbol lookups
0-v-0 Jun 20, 2026
37b36ba
Pack pointers in SymbolCacheEntry on 64bit platform
0-v-0 Jun 21, 2026
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66 changes: 62 additions & 4 deletions druntime/src/rt/trace.d
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Original file line number Diff line number Diff line change
Expand Up @@ -122,6 +122,49 @@ struct Symbol

enum ubyte SFvisited = 1; // visited

version (D_LP64)
{
struct SymbolCacheEntry
{
private:
ulong _packed;
uint _rest;
public:
uint length;

pragma(inline, true):
@property const(char)* ptr() const
{
return cast(const(char)*)(_packed & 0xFFFFFFFFFFFF);
}

@property void ptr(const(char)* p)
{
_packed = (_packed & 0xFFFF000000000000) | (cast(ulong)p & 0xFFFFFFFFFFFF);
}

@property Symbol* sym() const
{
return cast(Symbol*)(((_packed >> 48) & 0xFFFF) << 32 | _rest);
}

@property void sym(Symbol* s)
{
auto v = cast(ulong)s;
_packed = (_packed & 0xFFFFFFFFFFFF) | ((v >> 32) & 0xFFFF) << 48;
_rest = cast(uint)(v & 0xFFFFFFFF);
}
}
}
else
{
struct SymbolCacheEntry
{
const(char)* ptr;
uint length;
Symbol* sym;
}
}

//////////////////////////////////
// Build a linked list of these.
Expand All @@ -140,6 +183,7 @@ bool trace_inited;

Stack* stack_freelist;
Stack* trace_tos; // top of stack
SymbolCacheEntry[2048] trace_cache;

__gshared
{
Expand Down Expand Up @@ -639,7 +683,7 @@ private void trace_sympair_add(SymPair** psp, Symbol* s, ulong count)
//////////////////////////////////////////////
// This one is called by DMD

private extern(C) void trace_pro(char[] id)
private extern(C) void trace_pro(const(char)[] id)
{
//printf("trace_pro(ptr = %p, length = %lld)\n", id.ptr, id.length);
//printf("trace_pro(id = '%.*s')\n", id.length, id.ptr);
Expand All @@ -655,7 +699,22 @@ private extern(C) void trace_pro(char[] id)
if (id.length == 0)
return;
auto tos = stack_push();
auto s = trace_addsym(&root, id);

enum cacheMask = trace_cache.length - 1;
static assert((trace_cache.length & cacheMask) == 0);
const cacheIdx = (cast(size_t) id.ptr >> 4) & cacheMask;
auto centry = &trace_cache[cacheIdx];
Symbol* s;
if (centry.ptr == id.ptr && centry.length == id.length)
s = centry.sym;
else
{
s = trace_addsym(&root, id);
centry.ptr = id.ptr;
centry.length = cast(uint)id.length;
centry.sym = s;
}

tos.sym = s;
if (tos.prev)
{
Expand All @@ -677,8 +736,7 @@ private extern(C) void trace_pro(char[] id)
// Called by some old versions of DMD
extern(C) void _c_trace_pro(size_t idlen, char* idptr)
{
char[] id = idptr[0 .. idlen];
trace_pro(id);
trace_pro(idptr[0 .. idlen]);
}

/////////////////////////////////////////
Expand Down
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