Build the tail-calling interpreter using MSVC

Author: brandtbucher

Include/pyport.h

@@ -38,9 +38,10 @@
 
 // Static inline functions should use _Py_NULL rather than using directly NULL
 // to prevent C++ compiler warnings. On C23 and newer and on C++11 and newer,
-// _Py_NULL is defined as nullptr.
-#if (defined (__STDC_VERSION__) && __STDC_VERSION__ > 201710L) \
-        || (defined(__cplusplus) && __cplusplus >= 201103)
+// _Py_NULL is defined as nullptr (but not all compilers support it).
+#if (defined(__GNUC__) || defined(__clang__))                      \
+    && ((defined (__STDC_VERSION__) && __STDC_VERSION__ > 201710L) \
+        || (defined(__cplusplus) && __cplusplus >= 201103))
 #  define _Py_NULL nullptr
 #else
 #  define _Py_NULL NULL

PCbuild/build.bat

@@ -36,6 +36,7 @@ echo.                 overrides -c and -d
 echo.  --disable-gil  Enable experimental support for running without the GIL.
 echo.  --test-marker  Enable the test marker within the build.
 echo.  --regen        Regenerate all opcodes, grammar and tokens.
+echo.  --tail-call-interp          Enable the tail-calling interpreter.
 echo.  --experimental-jit          Enable the experimental just-in-time compiler.
 echo.  --experimental-jit-off      Ditto but off by default (PYTHON_JIT=1 enables).
 echo.  --experimental-jit-interpreter  Enable the experimental Tier 2 interpreter.
@@ -90,6 +91,7 @@ if "%~1"=="--disable-gil" (set UseDisableGil=true) & shift & goto CheckOpts
 if "%~1"=="--test-marker" (set UseTestMarker=true) & shift & goto CheckOpts
 if "%~1"=="-V" shift & goto Version
 if "%~1"=="--regen" (set Regen=true) & shift & goto CheckOpts
+if "%~1"=="--tail-call-interp" (set UseTailCalls=true) & shift & goto CheckOpts
 if "%~1"=="--experimental-jit" (set UseJIT=true) & (set UseTIER2=1) & shift & goto CheckOpts
 if "%~1"=="--experimental-jit-off" (set UseJIT=true) & (set UseTIER2=3) & shift & goto CheckOpts
 if "%~1"=="--experimental-jit-interpreter" (set UseTIER2=4) & shift & goto CheckOpts
@@ -186,6 +188,7 @@ echo on
  /p:IncludeSSL=%IncludeSSL% /p:IncludeTkinter=%IncludeTkinter%^
  /p:DisableGil=%UseDisableGil%^
  /p:UseTestMarker=%UseTestMarker% %GITProperty%^
+ /p:UseTailCalls=%UseTailCalls%^
  /p:UseJIT=%UseJIT%^
  /p:UseTIER2=%UseTIER2%^
  /p:PyStats=%PyStats%^

PCbuild/pythoncore.vcxproj

@@ -104,6 +104,8 @@
       <AdditionalIncludeDirectories Condition="$(IncludeExternals)">$(zlibDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <PreprocessorDefinitions>_USRDLL;Py_BUILD_CORE;Py_BUILD_CORE_BUILTIN;Py_ENABLE_SHARED;MS_DLL_ID="$(SysWinVer)";%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="$(IncludeExternals)">_Py_HAVE_ZLIB;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <AdditionalOptions Condition="'$(UseTailCalls)' == 'true'">/std:clatest %(AdditionalOptions)</AdditionalOptions>
+      <PreprocessorDefinitions Condition="'$(UseTailCalls)' == 'true'">Py_TAIL_CALL_INTERP=1;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="'$(UseJIT)' == 'true'">_Py_JIT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="'$(UseTIER2)' != '' and '$(UseTIER2)' != '0'">_Py_TIER2=$(UseTIER2);%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>

Python/ceval_macros.h

@@ -74,12 +74,18 @@
 #define TAIL_CALL_ARGS frame, stack_pointer, tstate, next_instr, oparg
 
 #if Py_TAIL_CALL_INTERP
-    // Note: [[clang::musttail]] works for GCC 15, but not __attribute__((musttail)) at the moment.
-#   define Py_MUSTTAIL [[clang::musttail]]
-#   define Py_PRESERVE_NONE_CC __attribute__((preserve_none))
-    Py_PRESERVE_NONE_CC typedef PyObject* (*py_tail_call_funcptr)(TAIL_CALL_PARAMS);
-
-#   define TARGET(op) Py_PRESERVE_NONE_CC PyObject *_TAIL_CALL_##op(TAIL_CALL_PARAMS)
+#   ifdef _MSC_VER
+#      define Py_MUSTTAIL [[msvc::musttail]]
+#      define Py_PRESERVE_NONE_CC __volatilecall
+#   else
+       // Note: [[clang::musttail]] works for GCC 15, but not __attribute__((musttail)) at the moment.
+#      define Py_MUSTTAIL [[clang::musttail]]
+#      define Py_PRESERVE_NONE_CC __attribute__((preserve_none))
+#   endif
+
+    typedef PyObject* (Py_PRESERVE_NONE_CC *py_tail_call_funcptr)(TAIL_CALL_PARAMS);
+
+#   define TARGET(op) PyObject *Py_PRESERVE_NONE_CC _TAIL_CALL_##op(TAIL_CALL_PARAMS)
 #   define DISPATCH_GOTO() \
         do { \
             Py_MUSTTAIL return (INSTRUCTION_TABLE[opcode])(TAIL_CALL_ARGS); \