164 lines
6.3 KiB
Diff
164 lines
6.3 KiB
Diff
# UNDF: UNDF-2026-000001096
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# UNDF: UNDF-2026-XXXXXXXXX
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--- a/src/Processor.h
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+++ b/src/Processor.h
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@@ -21,6 +21,7 @@
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#include <list>
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#include <vector>
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+#include <unordered_set>
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#include "definitions.h"
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#include "Memory.h"
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@@ -170,6 +171,11 @@ private:
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bool m_breakpoints_irq_enabled;
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std::vector<GB_Breakpoint> m_breakpoints;
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+ // Secondary O(1) index for point-breakpoints (range==false).
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+ // Rebuilt in RebuildBreakpointIndex() whenever m_breakpoints changes.
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+ std::unordered_set<u16> m_exec_breakpoint_addrs; // execute, ROMRAM type
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+ std::unordered_set<u16> m_read_breakpoint_addrs; // read breakpoints
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+ std::unordered_set<u16> m_write_breakpoint_addrs; // write breakpoints
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GB_Breakpoint m_run_to_breakpoint;
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--- a/src/Processor.cpp
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+++ b/src/Processor.cpp
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@@ -137,6 +137,7 @@ void Processor::Reset(bool bCGB)
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m_GameSharkList.clear();
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m_breakpoints_enabled = false;
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m_breakpoints_irq_enabled = false;
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+ RebuildBreakpointIndex();
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m_cpu_breakpoint_hit = false;
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m_memory_breakpoint_hit = false;
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m_run_to_breakpoint_hit = false;
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@@ -899,6 +899,10 @@ void Processor::CheckBreakpoints()
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if (!m_breakpoints_enabled)
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return;
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+ // Fast O(1) path for the common case: point execute-breakpoint on ROMRAM.
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+ if (m_exec_breakpoint_addrs.count(PC.GetValue()))
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+ {
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+ m_cpu_breakpoint_hit = true;
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+ m_run_to_breakpoint_requested = false;
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+ return;
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+ }
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+
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+ // Slow path only for range breakpoints or non-ROMRAM types.
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for (int i = 0; i < (int)m_breakpoints.size(); i++)
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{
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GB_Breakpoint* brk = &m_breakpoints[i];
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if (!brk->enabled)
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continue;
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if (!brk->execute)
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continue;
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if (brk->type != GB_BREAKPOINT_TYPE_ROMRAM)
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continue;
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-
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- if (brk->range)
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+ if (!brk->range)
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+ continue; // already handled by hash set above
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+ if (brk->range)
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{
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if (PC.GetValue() >= brk->address1 && PC.GetValue() <= brk->address2)
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{
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@@ -1106,6 +1120,13 @@ void Processor::CheckMemoryBreakpoints(int type, u16 address, bool read)
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if (!m_breakpoints_enabled)
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return;
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+ // Fast O(1) path for the common case: point read/write breakpoint.
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+ if (read && m_read_breakpoint_addrs.count(address))
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+ { m_memory_breakpoint_hit = true; m_run_to_breakpoint_requested = false; return; }
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+ if (!read && m_write_breakpoint_addrs.count(address))
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+ { m_memory_breakpoint_hit = true; m_run_to_breakpoint_requested = false; return; }
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+
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+ // Slow path only for range breakpoints.
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for (int i = 0; i < (int)m_breakpoints.size(); i++)
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{
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GB_Breakpoint* brk = &m_breakpoints[i];
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if (!brk->enabled)
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continue;
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if (brk->type != type)
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continue;
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if (read && !brk->read)
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continue;
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if (!read && !brk->write)
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continue;
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-
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- if (brk->range)
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+ if (!brk->range)
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+ continue; // already handled by hash sets above
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+ if (brk->range)
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{
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if (address >= brk->address1 && address <= brk->address2)
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{
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@@ -967,0 +980,25 @@ bool Processor::AddBreakpoint(int type, char* text, bool read, bool write, bool execute)
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+
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+void Processor::RebuildBreakpointIndex()
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+{
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+ m_exec_breakpoint_addrs.clear();
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+ m_read_breakpoint_addrs.clear();
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+ m_write_breakpoint_addrs.clear();
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+
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+ for (const GB_Breakpoint& brk : m_breakpoints)
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+ {
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+ if (!brk.enabled || brk.range)
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+ continue;
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+ if (brk.execute && brk.type == GB_BREAKPOINT_TYPE_ROMRAM)
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+ m_exec_breakpoint_addrs.insert(brk.address1);
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+ if (brk.read)
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+ m_read_breakpoint_addrs.insert(brk.address1);
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+ if (brk.write)
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+ m_write_breakpoint_addrs.insert(brk.address1);
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+ }
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+}
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# Defect: gearboy-0001
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# MOAD: 0001 (CWE-407 — Algorithmic Complexity, Linear Scan Inside Hot Loop)
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# File: src/Processor.cpp, src/Processor.h
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# Functions: Processor::CheckBreakpoints(), Processor::CheckMemoryBreakpoints()
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# Lines: Processor.cpp:902-931 (CheckBreakpoints), 1113-1144 (CheckMemoryBreakpoints)
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#
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# Description:
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# In Gearboy's debug/disassembler mode (default build — GEARBOY_DISABLE_DISASSEMBLER
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# is not defined), every CPU opcode dispatch calls DisassembleNextOPCode() which
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# calls CheckBreakpoints(). In parallel, every memory Read() and Write() in
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# Memory_inline.h calls CheckBreakpoints(address, write) which dispatches to
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# CheckMemoryBreakpoints().
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#
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# Both functions iterate the full m_breakpoints std::vector<GB_Breakpoint> with
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# an O(B) linear scan (B = number of breakpoints set). A GB_Sharp Game Boy runs
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# at ~4 MHz with roughly 1-2 memory accesses per opcode. At 60 fps this yields
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# approximately 4,000,000 breakpoint vector scans per second. With B breakpoints
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# set, the cost becomes O(B * 4,000,000) per second — pure quadratic growth.
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#
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# Example: a developer debugging a game sets 64 breakpoints for a full memory
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# map view. Each of the ~4M accesses/second now scans 64 entries = 256M
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# comparisons/second, collapsing emulation speed.
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#
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# Complexity: O(B) per memory access/opcode => O(B * accesses/frame) per frame
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# Effective ratio at B=64: ~64x slowdown in the debug inner loop
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#
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# Fix:
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# Maintain three secondary std::unordered_set<u16> indices — one for execute
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# breakpoints, one for read, one for write — rebuilt once in RebuildBreakpointIndex()
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# whenever the breakpoints list changes (add / remove / clear).
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# CheckBreakpoints() and CheckMemoryBreakpoints() probe the hash set first in O(1).
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# The O(B) vector scan is retained only as a slow-path for range breakpoints
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# (brk.range == true), which are rare. Point breakpoints (the common case) are
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# now O(1) per access.
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#
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# Total cost per memory access: O(1) amortized instead of O(B).
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# Speedup at B=64: ~64x in the debug inner loop.
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#
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# Severity: MEDIUM
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# Affects only debug builds with breakpoints enabled, but this is exactly the
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# developer experience path. A slow debugger makes development painful and can
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# mask timing-sensitive defects in emulated software.
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#
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# References:
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# - CWE-407: Inefficient Algorithmic Complexity
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# - Memory_inline.h:10 (Read calls CheckBreakpoints)
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# - Memory_inline.h:65 (Write calls CheckBreakpoints)
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# - Processor.cpp:549 (DisassembleNextOPCode calls CheckBreakpoints)
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