bpo-45412: Move _Py_SET_53BIT_PRECISION_START to pycore_pymath.h (GH-28882)

Move the following macros , to pycore_pymath.h (internal C API):

* _Py_SET_53BIT_PRECISION_HEADER
* _Py_SET_53BIT_PRECISION_START
* _Py_SET_53BIT_PRECISION_END

PEP 7: add braces to if and "do { ... } while (0)" in these macros.

Move also _Py_get_387controlword() and _Py_set_387controlword()
definitions to pycore_pymath.h. These functions are no longer
exported.

pystrtod.c now includes pycore_pymath.h.

1 files changed, 91 insertions, 0 deletions

diff --git a/Include/internal/pycore_pymath.h b/Include/internal/pycore_pymath.h
index e4d5778..b1a2004 100644
--- a/Include/internal/pycore_pymath.h
+++ b/Include/internal/pycore_pymath.h
@@ -74,6 +74,97 @@ static inline void _Py_ADJUST_ERANGE2(double x, double y)
 #define _Py_InIntegralTypeRange(type, v) \
     (_Py_IntegralTypeMin(type) <= v && v <= _Py_IntegralTypeMax(type))
 
+
+//--- Implementation of the HAVE_PY_SET_53BIT_PRECISION macro -------------
+//--- defined in pyport.h -------------------------------------------------
+//
+// Give appropriate definitions for the following three macros:
+//
+//    _Py_SET_53BIT_PRECISION_HEADER : any variable declarations needed to
+//        use the two macros below.
+//    _Py_SET_53BIT_PRECISION_START : store original FPU settings, and
+//        set FPU to 53-bit precision/round-half-to-even
+//    _Py_SET_53BIT_PRECISION_END : restore original FPU settings
+
+// Get and set x87 control word for gcc/x86
+#ifdef HAVE_GCC_ASM_FOR_X87
+
+// Functions defined in Python/pymath.c
+extern unsigned short _Py_get_387controlword(void);
+extern void _Py_set_387controlword(unsigned short);
+
+#define _Py_SET_53BIT_PRECISION_HEADER                                  \
+    unsigned short old_387controlword, new_387controlword
+#define _Py_SET_53BIT_PRECISION_START                                   \
+    do {                                                                \
+        old_387controlword = _Py_get_387controlword();                  \
+        new_387controlword = (old_387controlword & ~0x0f00) | 0x0200;   \
+        if (new_387controlword != old_387controlword) {                 \
+            _Py_set_387controlword(new_387controlword);                 \
+        }                                                               \
+    } while (0)
+#define _Py_SET_53BIT_PRECISION_END                                     \
+    do {                                                                \
+        if (new_387controlword != old_387controlword) {                 \
+            _Py_set_387controlword(old_387controlword);                 \
+        }                                                               \
+    } while (0)
+#endif
+
+// Get and set x87 control word for VisualStudio/x86.
+// x87 is not supported in 64-bit or ARM.
+#if defined(_MSC_VER) && !defined(_WIN64) && !defined(_M_ARM)
+#define _Py_SET_53BIT_PRECISION_HEADER \
+    unsigned int old_387controlword, new_387controlword, out_387controlword
+    // We use the __control87_2 function to set only the x87 control word.
+    // The SSE control word is unaffected.
+#define _Py_SET_53BIT_PRECISION_START                                   \
+    do {                                                                \
+        __control87_2(0, 0, &old_387controlword, NULL);                 \
+        new_387controlword =                                            \
+          (old_387controlword & ~(_MCW_PC | _MCW_RC)) | (_PC_53 | _RC_NEAR); \
+        if (new_387controlword != old_387controlword) {                 \
+            __control87_2(new_387controlword, _MCW_PC | _MCW_RC,        \
+                          &out_387controlword, NULL);                   \
+        }                                                               \
+    } while (0)
+#define _Py_SET_53BIT_PRECISION_END                                     \
+    do {                                                                \
+        if (new_387controlword != old_387controlword) {                 \
+            __control87_2(old_387controlword, _MCW_PC | _MCW_RC,        \
+                          &out_387controlword, NULL);                   \
+        }                                                               \
+    } while (0)
+#endif
+
+#ifdef HAVE_GCC_ASM_FOR_MC68881
+#define _Py_SET_53BIT_PRECISION_HEADER \
+    unsigned int old_fpcr, new_fpcr
+#define _Py_SET_53BIT_PRECISION_START                                   \
+    do {                                                                \
+        __asm__ ("fmove.l %%fpcr,%0" : "=g" (old_fpcr));                \
+        /* Set double precision / round to nearest.  */                 \
+        new_fpcr = (old_fpcr & ~0xf0) | 0x80;                           \
+        if (new_fpcr != old_fpcr) {                                     \
+              __asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (new_fpcr));\
+        }                                                               \
+    } while (0)
+#define _Py_SET_53BIT_PRECISION_END                                     \
+    do {                                                                \
+        if (new_fpcr != old_fpcr) {                                     \
+            __asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (old_fpcr));  \
+        }                                                               \
+    } while (0)
+#endif
+
+// Default definitions are empty
+#ifndef _Py_SET_53BIT_PRECISION_HEADER
+#  define _Py_SET_53BIT_PRECISION_HEADER
+#  define _Py_SET_53BIT_PRECISION_START
+#  define _Py_SET_53BIT_PRECISION_END
+#endif
+
+
 #ifdef __cplusplus
 }
 #endif