/* * Written by J.T. Conklin . * Public domain. * * Changed to use fyl2xp1 for values near 1, . */ #include .section .rodata.cst8,"aM",@progbits,8 .p2align 3 .type one,@object one: .double 1.0 ASM_SIZE_DIRECTIVE(one) /* It is not important that this constant is precise. It is only a value which is known to be on the safe side for using the fyl2xp1 instruction. */ .type limit,@object limit: .double 0.29 ASM_SIZE_DIRECTIVE(limit) #ifdef PIC # define MO(op) op##@GOTOFF(%edx) #else # define MO(op) op #endif .text ENTRY(__ieee754_log10) fldlg2 // log10(2) fldl 4(%esp) // x : log10(2) #ifdef PIC LOAD_PIC_REG (dx) #endif fxam fnstsw fld %st // x : x : log10(2) sahf jc 3f // in case x is NaN or ħInf 4: fsubl MO(one) // x-1 : x : log10(2) fld %st // x-1 : x-1 : x : log10(2) fabs // |x-1| : x-1 : x : log10(2) fcompl MO(limit) // x-1 : x : log10(2) fnstsw // x-1 : x : log10(2) andb $0x45, %ah jz 2f fxam fnstsw andb $0x45, %ah cmpb $0x40, %ah jne 5f fabs // log10(1) is +0 in all rounding modes. 5: fstp %st(1) // x-1 : log10(2) fyl2xp1 // log10(x) ret 2: fstp %st(0) // x : log10(2) fyl2x // log10(x) ret 3: jp 4b // in case x is ħInf fstp %st(1) fstp %st(1) ret END (__ieee754_log10) strong_alias (__ieee754_log10, __log10_finite)