partial revert of the commit 4ad186c5ef

A test program:

    /* result of the new version inroduced in 4ad186c5ef: t2a = 44100312 */
    #include<stdio.h>
    int main() {
	int t1 = 176401255;
	float f = 0.25f;
	int t2a = (int)(t1 * f); // must be 44100313
	int t2b = (int)(t1 * (float)0.25f);
	printf("t2a=%d t2b=%d \n",t2a,t2b);
	return 0;
    }

i386-gen.c

@@ -982,6 +982,28 @@ ST_FUNC void gen_cvt_itof(int t)
 /* convert fp to int 't' type */
 ST_FUNC void gen_cvt_ftoi(int t)
 {
+ #ifndef COMMIT_4ad186c5ef61_IS_FIXED
+    /* a good version but it takes a more time to execute */
+    gv(RC_FLOAT);
+    save_reg(TREG_EAX);
+    save_reg(TREG_EDX);
+    gen_static_call(TOK___tcc_cvt_ftol);
+    vtop->r = TREG_EAX; /* mark reg as used */
+    if (t == VT_LLONG)
+        vtop->r2 = TREG_EDX;
+ #else
+    /* a new version with a bug: t2a = 44100312 */
+    /*
+    #include<stdio.h>
+    int main() {
+	int t1 = 176401255;
+	float f = 0.25f;
+	int t2a = (int)(t1 * f); // must be 44100313
+	int t2b = (int)(t1 * (float)0.25f);
+	printf("t2a=%d t2b=%d \n",t2a,t2b);
+	return 0;
+    }
+    */
     int bt = vtop->type.t & VT_BTYPE;
     if (bt == VT_FLOAT)
         vpush_global_sym(&func_old_type, TOK___fixsfdi);
@@ -994,6 +1016,7 @@ ST_FUNC void gen_cvt_ftoi(int t)
     vpushi(0);
     vtop->r = REG_IRET;
     vtop->r2 = REG_LRET;
+ #endif
 }
 
 /* convert from one floating point type to another */

lib/libtcc1.c

@@ -480,6 +480,20 @@ long long __ashldi3(long long a, int b)
 #endif
 }
 
+#ifndef COMMIT_4ad186c5ef61_IS_FIXED
+long long __tcc_cvt_ftol(long double x)
+{
+    unsigned c0, c1;
+    long long ret;
+    __asm__ __volatile__ ("fnstcw %0" : "=m" (c0));
+    c1 = c0 | 0x0C00;
+    __asm__ __volatile__ ("fldcw %0" : : "m" (c1));
+    __asm__ __volatile__ ("fistpll %0"  : "=m" (ret));
+    __asm__ __volatile__ ("fldcw %0" : : "m" (c0));
+    return ret;
+}
+#endif
+
 #endif /* !__x86_64__ */
 
 /* XXX: fix tcc's code generator to do this instead */

tcctok.h

@@ -229,6 +229,10 @@
      DEF(TOK___fixsfdi, "__fixsfdi")
      DEF(TOK___fixdfdi, "__fixdfdi")
      DEF(TOK___fixxfdi, "__fixxfdi")
+
+ #ifndef COMMIT_4ad186c5ef61_IS_FIXED
+     DEF(TOK___tcc_cvt_ftol, "__tcc_cvt_ftol")
+ #endif
 #endif
 
 #if defined TCC_TARGET_I386 || defined TCC_TARGET_X86_64