osd: Added helper for getting CPU cache line size.

src/devices/cpu/drcbex64.cpp

@@ -945,8 +945,21 @@ void drcbe_x64::generate(drcuml_block &block, const instruction *instlist, uint3
 	m_hash.block_begin(block, instlist, numinst);
 	m_map.block_begin(block);
 
-	// compute the base by aligning the cache top to a cache line (assumed to be 64 bytes)
-	x86code *dst = (x86code *)(uint64_t(m_cache.top() + 63) & ~63);
+	// compute the base by aligning the cache top to a cache line
+	auto [err, linesize] = osd_get_cache_line_size();
+	uintptr_t linemask = 63;
+	if (err)
+	{
+		osd_printf_verbose("Error getting cache line size (%s:%d %s), assuming 64 bytes\n", err.category().name(), err.value(), err.message());
+	}
+	else
+	{
+		assert(linesize);
+		linemask = linesize - 1;
+		for (unsigned shift = 1; linemask & (linemask + 1); ++shift)
+			linemask |= linemask >> shift;
+	}
+	x86code *dst = (x86code *)(uintptr_t(m_cache.top() + linemask) & ~linemask);
 
 	CodeHolder ch;
 	ch.init(Environment::host(), uint64_t(dst));

src/devices/cpu/drcbex86.cpp

@@ -840,8 +840,20 @@ void drcbe_x86::generate(drcuml_block &block, const instruction *instlist, uint3
 	m_hash.block_begin(block, instlist, numinst);
 	m_map.block_begin(block);
 
-	// compute the base by aligning the cache top to a cache line (assumed to be 64 bytes)
-	x86code *dst = (x86code *)(uint64_t(m_cache.top() + 63) & ~63);
+	// compute the base by aligning the cache top to a cache line
+	auto [err, linesize] = osd_get_cache_line_size();
+	uintptr_t linemask = 63;
+	if (err)
+	{
+		osd_printf_verbose("Error getting cache line size (%s:%d %s), assuming 64 bytes\n", err.category().name(), err.value(), err.message());
+	}
+	else
+	{
+		assert(linesize);
+		linemask = linesize - 1;
+		for (unsigned shift = 1; linemask & (linemask + 1); ++shift)
+			linemask |= linemask >> shift;
+	}
 
 	CodeHolder ch;
 	ch.init(Environment::host(), uint64_t(dst));

src/osd/modules/lib/osdlib_macosx.cpp

@@ -56,6 +56,7 @@ void osd_process_kill()
 	kill(getpid(), SIGKILL);
 }
 
+
 //============================================================
 //  osd_break_into_debugger
 //============================================================
@@ -81,6 +82,22 @@ void osd_break_into_debugger(const char *message)
 }
 
 
+//============================================================
+//  osd_get_cache_line_size
+//============================================================
+
+std::pair<std::error_condition, unsigned> osd_get_cache_line_size() noexcept
+{
+	size_t result = 0;
+	size_t resultsize = sizeof(result);
+	int const err = sysctlbyname("hw.cachelinesize", &result, &resultsize, 0, 0);
+	if (!err)
+		return std::make_pair(std::error_condition(), unsigned(result));
+	else
+		return std::make_pair(std::error_condition(err, std::generic_category()), 0U);
+}
+
+
 //============================================================
 //  osd_get_clipboard_text
 //============================================================

src/osd/modules/lib/osdlib_unix.cpp

@@ -53,6 +53,7 @@ void osd_process_kill()
 	kill(getpid(), SIGKILL);
 }
 
+
 //============================================================
 //  osd_break_into_debugger
 //============================================================
@@ -68,6 +69,31 @@ void osd_break_into_debugger(const char *message)
 #endif
 }
 
+
+//============================================================
+//  osd_get_cache_line_size
+//============================================================
+
+std::pair<std::error_condition, unsigned> osd_get_cache_line_size() noexcept
+{
+#if defined(__linux__)
+	FILE *const f = std::fopen("/sys/devices/system/cpu/cpu0/cache/index0/coherency_line_size", "r");
+	if (!f)
+		return std::make_pair(std::error_condition(errno, std::generic_category()), 0U);
+
+	unsigned result = 0;
+	auto const cnt = std::fscanf(f, "%u", &result);
+	std::fclose(f);
+	if (1 == cnt)
+		return std::make_pair(std::error_condition(), result);
+	else
+		return std::make_pair(std::errc::io_error, 0U);
+#else // defined(__linux__)
+	return std::make_pair(std::errc::not_supported, 0U);
+#endif
+}
+
+
 #ifdef SDLMAME_ANDROID
 std::string osd_get_clipboard_text() noexcept
 {

src/osd/modules/lib/osdlib_win32.cpp

@@ -106,6 +106,42 @@ void osd_break_into_debugger(const char *message)
 #endif
 }
 
+
+//============================================================
+//  osd_get_cache_line_size
+//============================================================
+
+std::pair<std::error_condition, unsigned> osd_get_cache_line_size() noexcept
+{
+	DWORD resultsize = 0;
+	if (GetLogicalProcessorInformation(nullptr, &resultsize) || (ERROR_INSUFFICIENT_BUFFER != GetLastError()) || !resultsize)
+		return std::make_pair(std::errc::operation_not_permitted, 0U);
+
+	auto const result = reinterpret_cast<SYSTEM_LOGICAL_PROCESSOR_INFORMATION *>(std::malloc(resultsize));
+	if (!result)
+		return std::make_pair(std::errc::not_enough_memory, 0U);
+
+	if (!GetLogicalProcessorInformation(result, &resultsize))
+	{
+		std::free(result);
+		return std::make_pair(std::errc::operation_not_permitted, 0U);
+	}
+
+	for (unsigned i = 0; i < (resultsize / sizeof(result[0])); ++i)
+	{
+		if ((RelationCache == result[i].Relationship) && (1 == result[i].Cache.Level))
+		{
+			unsigned const linesize = result[i].Cache.LineSize;
+			std::free(result);
+			return std::make_pair(std::error_condition(), linesize);
+		}
+	}
+
+	std::free(result);
+	return std::make_pair(std::errc::operation_not_permitted, 0U);
+}
+
+
 //============================================================
 //  get_clipboard_text_by_format
 //============================================================

src/osd/osdcore.h

@@ -19,6 +19,7 @@
 #include <iosfwd>
 #include <string>
 #include <string_view>
+#include <system_error>
 #include <utility>
 #include <vector>
 
@@ -128,6 +129,8 @@ osd_ticks_t osd_ticks_per_second() noexcept;
 -----------------------------------------------------------------------------*/
 void osd_sleep(osd_ticks_t duration) noexcept;
 
+
+
 /***************************************************************************
     WORK ITEM INTERFACES
 ***************************************************************************/
@@ -350,6 +353,14 @@ void osd_work_item_release(osd_work_item *item);
 void osd_break_into_debugger(const char *message);
 
 
+/// \brief Get cache line size in bytes
+///
+/// This function gets the host CPU's level 1 cache line size in bytes.
+/// \return A pair consisting of an error condition and the cache line
+///   size in bytes if successful.
+std::pair<std::error_condition, unsigned> osd_get_cache_line_size() noexcept;
+
+
 
 /***************************************************************************
     UNCATEGORIZED INTERFACES