static void f2xm1(FPU_REG *st0_ptr, u_char tag) { FPU_REG a; clear_C1(); if ( tag == TAG_Valid ) { /* For an 80486 FPU, the result is undefined if the arg is >= 1.0 */ if ( exponent(st0_ptr) < 0 ) { denormal_arg: FPU_to_exp16(st0_ptr, &a); /* poly_2xm1(x) requires 0 < st(0) < 1. */ poly_2xm1(getsign(st0_ptr), &a, st0_ptr); } set_precision_flag_up(); /* 80486 appears to always do this */ return; } if ( tag == TAG_Zero ) return; if ( tag == TAG_Special ) tag = FPU_Special(st0_ptr); switch ( tag ) { case TW_Denormal: if ( denormal_operand() < 0 ) return; goto denormal_arg; case TW_Infinity: if ( signnegative(st0_ptr) ) { /* -infinity gives -1 (p16-10) */ FPU_copy_to_reg0(&CONST_1, TAG_Valid); setnegative(st0_ptr); } return; default: single_arg_error(st0_ptr, tag); } }
static void f2xm1(FPU_REG *st0_ptr, u_char tag) { FPU_REG a; clear_C1(); if (tag == TAG_Valid) { if (exponent(st0_ptr) < 0) { denormal_arg: FPU_to_exp16(st0_ptr, &a); poly_2xm1(getsign(st0_ptr), &a, st0_ptr); } set_precision_flag_up(); return; } if (tag == TAG_Zero) return; if (tag == TAG_Special) tag = FPU_Special(st0_ptr); switch (tag) { case TW_Denormal: if (denormal_operand() < 0) return; goto denormal_arg; case TW_Infinity: if (signnegative(st0_ptr)) { FPU_copy_to_reg0(&CONST_1, TAG_Valid); setnegative(st0_ptr); } return; default: single_arg_error(st0_ptr, tag); } }