diff options
Diffstat (limited to 'sysdeps/i386/fpu/e_powl.S')
| -rw-r--r-- | sysdeps/i386/fpu/e_powl.S | 78 |
1 files changed, 20 insertions, 58 deletions
diff --git a/sysdeps/i386/fpu/e_powl.S b/sysdeps/i386/fpu/e_powl.S index cc6dcd1a88..44cf23880a 100644 --- a/sysdeps/i386/fpu/e_powl.S +++ b/sysdeps/i386/fpu/e_powl.S @@ -151,7 +151,7 @@ ENTRY(__ieee754_powl) fcompl MO(p3) // y : x fnstsw sahf - jnc 2f + jnc 3f popl %eax cfi_adjust_cfa_offset (-4) popl %edx @@ -166,12 +166,22 @@ ENTRY(__ieee754_powl) 4: fldl MO(one) // 1 : x fxch + /* If y is even, take the absolute value of x. Otherwise, + ensure all intermediate values that might overflow have the + sign of x. */ + testb $1, %al + jnz 6f + fabs + 6: shrdl $1, %edx, %eax jnc 5f fxch + fabs fmul %st(1) // x : ST*x fxch -5: fmul %st(0), %st // x*x : ST*x +5: fld %st // x : x : ST*x + fabs // |x| : x : ST*x + fmulp // |x|*x : ST*x shrl $1, %edx movl %eax, %ecx orl %edx, %ecx @@ -198,79 +208,31 @@ ENTRY(__ieee754_powl) cfi_adjust_cfa_offset (8) .align ALIGNARG(4) -2: // y is a large integer (absolute value at least 8), but - // may be odd unless at least 1L<<64. So it may be necessary - // to adjust the sign of a negative result afterwards. - fxch // x : y - fabs // |x| : y - fxch // y : |x| +2: // y is a large integer (absolute value at least 1L<<63). // If y has absolute value at least 1L<<78, then any finite // nonzero x will result in 0 (underflow), 1 or infinity (overflow). // Saturate y to those bounds to avoid overflow in the calculation // of y*log2(x). - fld %st // y : y : |x| - fabs // |y| : y : |x| - fcompl MO(p78) // y : |x| + fld %st // y : y : x + fabs // |y| : y : x + fcompl MO(p78) // y : x fnstsw sahf jc 3f fstp %st(0) // pop y - fldl MO(p78) // 1L<<78 : |x| + fldl MO(p78) // 1L<<78 : x testb $2, %dl jz 3f // y > 0 - fchs // -(1L<<78) : |x| + fchs // -(1L<<78) : x .align ALIGNARG(4) 3: /* y is a real number. */ subl $28, %esp cfi_adjust_cfa_offset (28) fstpt 12(%esp) // x fstpt (%esp) // <empty> - mov %edx, 24(%esp) call HIDDEN_JUMPTARGET (__powl_helper) // <result> - mov 24(%esp), %edx - addl $28, %esp - cfi_adjust_cfa_offset (-28) - testb $2, %dh - jz 292f - // x is negative. If y is an odd integer, negate the result. -#ifdef PIC - LOAD_PIC_REG (cx) -#endif - fldt 24(%esp) // y : abs(result) - fld %st // y : y : abs(result) - fabs // |y| : y : abs(result) - fcompl MO(p64) // y : abs(result) - fnstsw - sahf - jnc 291f - fldl MO(p63) // p63 : y : abs(result) - fxch // y : p63 : abs(result) - fprem // y%p63 : p63 : abs(result) - fstp %st(1) // y%p63 : abs(result) - - // We must find out whether y is an odd integer. - fld %st // y : y : abs(result) - fistpll (%esp) // y : abs(result) - fildll (%esp) // int(y) : y : abs(result) - fucompp // abs(result) - fnstsw - sahf - jne 292f - - // OK, the value is an integer, but is it odd? - popl %eax - cfi_adjust_cfa_offset (-4) - popl %edx - cfi_adjust_cfa_offset (-4) - andb $1, %al - jz 290f // jump if not odd - // It's an odd integer. - fchs -290: ret - cfi_adjust_cfa_offset (8) -291: fstp %st(0) // abs(result) -292: addl $8, %esp - cfi_adjust_cfa_offset (-8) + addl $36, %esp + cfi_adjust_cfa_offset (-36) ret // pow(x,±0) = 1 |