From 13a18906ef320546d0aff2bbaa794c896462a640 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tyge=20L=C3=B8vset?= <tylo@norceresearch.no>
Date: Wed, 25 Nov 2020 14:29:42 +0100
Subject: [PATCH] win32 tcc_libm.h: Implemented overrides for msvcrt.dll's
 frexp(), ldexp(), and fabs() with speedups 4.5X, 7.3X and 6.3X
 correspondingly. This is the last commit on this for now.

---
 win32/include/tcc/tcc_libm.h | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/win32/include/tcc/tcc_libm.h b/win32/include/tcc/tcc_libm.h
index 19453320..cb256fe1 100644
--- a/win32/include/tcc/tcc_libm.h
+++ b/win32/include/tcc/tcc_libm.h
@@ -232,6 +232,23 @@ __CRT_INLINE double __cdecl scalbn(double x, int n) {
   return x * u.f;
 }
 
+/* MUSL: Override msvcrt frexp(): 4.5x speedup! */
+
+__CRT_INLINE double __cdecl frexp(double x, int *e) {
+  union {double f; uint64_t i;} u = {.f = x};
+  int ee = u.i>>52 & 0x7ff;
+  if (!ee) {
+    if (x) x = frexp(x*0x1p64, e), *e -= 64;
+    else *e = 0;
+    return x;
+  } else if (ee == 0x7ff)
+    return x;
+  *e = ee - 0x3fe;
+  u.i &= 0x800fffffffffffffull;
+  u.i |= 0x3fe0000000000000ull;
+  return u.f;
+}
+
 /* MUSL nan */
 
 __CRT_INLINE double __cdecl nan(const char* s) {
@@ -273,7 +290,11 @@ __CRT_INLINE long double __cdecl scalblnl(long double x, long n) {
   return scalbn(x, n);
 }
 
+/* Override msvcrt ldexp(): 7.3x speedup! */
 
+__CRT_INLINE double __cdecl ldexp(double x, int expn) {
+  return scalbn(x, expn);
+}
 __CRT_INLINE float __cdecl ldexpf(float x, int expn) {
   return scalbn(x, expn);
 }
@@ -391,14 +412,16 @@ __CRT_INLINE long double __cdecl nexttowardl(long double x, long double to) {
   return nextafter(x, to);
 }
 
+/* Override msvcrt fabs(): 6.3x speedup! */
 
-__CRT_INLINE float __cdecl fabsf (float x) {
-  union {float f; uint32_t i;} u = {.f = x};
-  u.i &= 0x7fffffff; return u.f;
+__CRT_INLINE double __cdecl fabs(double x) {
+  return x < 0 ? -x : x;
 }
-__CRT_INLINE long double __cdecl fabsl (long double x) {
-  union {double f; uint64_t i;} u = {.f = x};
-  u.i &= 0x7fffffffffffffff; return u.f;
+__CRT_INLINE float __cdecl fabsf(float x) {
+  return x < 0 ? -x : x;
+}
+__CRT_INLINE long double __cdecl fabsl(long double x) {
+  return x < 0 ? -x : x;
 }