/ nextaft.s (emx+gcc) -- Copyright (c) 1996-1998 by Eberhard Mattes #include #define FUNC MATHSUFFIX2(nextafter) .globl LABEL(FUNC) .text ALIGN #if defined (LONG_DOUBLE) / long double nextafterl (long double x, long double y) #define x(i) 4+i(%esp) #define y(i) 16+i(%esp) LABEL(FUNC): PROFILE_NOFRAME fldt x(0) fldt y(0) fucompp fstsww %ax testb $0x04, %ah jnz Lunordered /* Unordered (at least one NaN) */ testb $0x40, %ah jnz Leq /* x==y */ movb x(9), %al shrb $7, %al /* signbit(x) -> bit 0 of %al */ xorb %ah, %al /* Note: bit 0 of %ah is 1 iff x>y */ testb $0x01, %al movw x(8), %ax /* Fetch exponent */ jnz Ldown /* Decrement mantissa */ /* Increment mantissa. */ Lup: andl $0x7fff, %eax /* Clear sign bit */ cmpl $0x7fff, %eax /* Infinity? */ je Lreturn_x /* Yes => return x */ addl $1, x(0) /* Increment lower word */ adcl $0, x(4) /* Propagate carry into upper word */ jc Lup_of /* Overflow */ testl %eax, %eax /* Denormal? */ jnz Lreturn_x /* No => return x */ testb $0x80, x(7) /* Pseudo-denormal? */ jz Lreturn_x_exception /* No => return x, raise exceptions */ incw x(8) /* Turn it into a normal */ jmp Lreturn_x /* Return x and raise appropriate exceptions (inexact and underflow/overflow). */ ALIGN Lreturn_x_exception: fldt x(0) fstl y(0) /* This raises the exceptions */ jmp Lreturn /* (we store as 64-bit number!) */ /* Mantissa overflow. Increment exponent. */ ALIGN Lup_of: cmpl $0x7ffe, %eax /* Exponent overflow? */ je Lup_make_inf /* Yes => return infinity */ movb $0x80, x(7) /* Set mantissa to 100...000 */ incw x(8) /* Increment exponent */ jmp Lreturn_x /* Return x */ /* x is LDBL_MAX, raise overflow and inexact exceptions, return infinity. */ ALIGN Lup_make_inf: movl $0xffffffff, x(0) /* Restore mantissa of x */ movl $0xffffffff, x(4) fldt x(0) /* Compute x+x */ fadd %st jmp Lreturn /* Decrement mantissa. */ ALIGN Ldown: andl $0x7fff, %eax /* Clear sign bit */ cmpl $0x7fff, %eax /* Infinity? */ je Ldown_is_inf /* Yes => return biggest normal */ subl $1, x(0) /* Decrement lower word */ sbbl $0, x(4) /* Propagate carry into upper word */ jc Ldown_uf0 /* Underflow (integer bit was 0) */ jo Ldown_uf1 /* Underflow (integer bit was 1) */ test %eax, %eax /* Is the exponent zero? */ jnz Lreturn_x /* No => return x */ jmp Lreturn_x_exception /* Yes => maybe raise exceptions */ /* Underflow (mantissa was 100...000 and is now 011...111). Decrement the exponent. Return the biggest denormal if the exponent becomes 0. */ ALIGN Ldown_uf1: decw x(8) /* Decrement exponent */ cmp $1, %eax /* Exponent now zero? */ je Lreturn_x_exception /* Yes => return x (mantissa OK) */ /* It's still a normal. Set the mantissa to 111...111. */ orb $0x80, x(7) jmp Lreturn_x /* Underflow (mantissa was 000...000 and is now 111...111. Return the smallest denormal with y's sign. */ ALIGN Ldown_uf0: movl $1, y(0) movl $0, y(4) andw $0x8000, y(8) fldt y(0) fstl y(0) /* This raises the exceptions */ jmp Lreturn /* x is infinite. Return the biggest normal with x's sign. */ ALIGN Ldown_is_inf: movl $0xffffffff, x(0) movl $0xffffffff, x(4) andw $0x8000, x(8) orw $0x7ffe, x(8) jmp Lreturn_x /* Unordered: return one of the NaNs. */ ALIGN Lunordered: fldt x(0) _xam j_nan Lreturn /* x is a Nan => return x */ fstp %st(0) /* Remove x */ /* Fall through to return y */ /* x==y: return y. */ ALIGN Leq: fldt y(0) jmp Lreturn ALIGN Lreturn_x: fldt x(0) ALIGN Lreturn: EPILOGUE(FUNC) #elif defined (FLOAT) / float nextafterf (float x, float y) #define x 4(%esp) #define y 8(%esp) LABEL(FUNC): PROFILE_NOFRAME flds x flds y fucompp fstsww %ax testb $0x04, %ah jnz Lunordered /* Unordered (at least one NaN) */ testb $0x40, %ah jnz Leq /* x==y */ movl x, %edx shrl $31, %edx /* signbit(x) -> bit 0 of %dl */ xorb %ah, %dl /* Note: bit 0 of %ah is 1 iff x>y */ testb $0x01, %dl movl $1, %ecx /* Increment */ jz Lcommon movl $-1, %ecx /* TODO: Do this without jump */ ALIGN Lcommon:movl x, %eax andl $0x7fffffff, %eax /* Clear sign bit */ jz Lx_zero /* x = 0.0 => smallest denormal */ addl %ecx, x movl x, %edx andl $0x7fffffff, %edx jz Lreturn_x /* 0.0 => no underflow */ cmpl $0x7f800000, %edx je Loverflow cmpl $0x00800000, %edx jb Lunderflow ALIGN Lreturn_x: flds x ALIGN Lreturn: EPILOGUE(FUNC) ALIGN Lx_zero: movl y, %eax andl $0x80000000, %eax /* Extract sign bit of y */ orl $0x00000001, %eax /* Smallest denormal */ movl %eax, x ALIGN Lunderflow: fldl Lsmall fstps y jmp Lreturn_x ALIGN Loverflow: fldl Lbig fstps y /* Raise overflow and inexact */ jmp Lreturn_x ALIGN Lunordered: movl x, %eax andl $0x7fffffff, %eax cmpl $0x7f800000, %eax ja Lreturn_x /* x is a NaN => return x */ /* Fall through to return y (which is a NaN) */ ALIGN Leq: flds y jmp Lreturn Lsmall: .long 0x00000001, 0x00000000 Lbig: .long 0xffffffff, 0x7fefffff #else / double nextafter (double x, double y) #define x(i) 4+i(%esp) #define y(i) 12+i(%esp) LABEL(FUNC): PROFILE_NOFRAME fldl x(0) fldl y(0) fucompp fstsww %ax testb $0x04, %ah jnz Lunordered /* Unordered (at least one NaN) */ testb $0x40, %ah jnz Leq /* x==y */ movb x(7), %dl shrb $7, %dl /* signbit(x) -> bit 0 of %dl */ xorb %ah, %dl /* Note: bit 0 of %ah is 1 iff x>y */ movl x(4), %eax andl $0x7fffffff, %eax /* Clear sign bit */ orl x(0), %eax /* x == 0.0? */ jz Lx_zero /* Yes => smallest denormal */ testb $0x01, %dl jnz Ldec addl $1, x(0) adcl $0, x(4) ALIGN Lcommon:movl x(4), %eax andl $0x7fffffff, %eax /* Clear sign bit */ orl x(0), %eax jz Lreturn_x /* 0.0 => no underflow */ movl x(4), %eax andl $0x7ff00000, %eax /* Extract exponent */ cmpl $0x7ff00000, %eax je Loverflow cmpl $0x00100000, %eax jb Lunderflow ALIGN Lreturn_x: fldl x(0) ALIGN Lreturn: EPILOGUE(FUNC) ALIGN Ldec: subl $1, x(0) sbbl $0, x(4) jmp Lcommon ALIGN Lx_zero: andl $0x80000000, y(4) /* Keep sign bit of y */ movl $0x00000001, y(0) /* Smallest denormal */ fldl Lsmall fstps x(0) fldl y(0) jmp Lreturn ALIGN Lunderflow: fldl Lsmall fstps y(0) jmp Lreturn_x ALIGN Loverflow: fldl Lbig fstps y(0) /* Raise overflow and inexact */ jmp Lreturn_x ALIGN Lunordered: movl x(4), %eax andl $0x7fffffff, %eax cmpl $0x7ff80000, %eax jae Lreturn_x /* x is a NaN => return x */ /* Fall through to return y (which is a NaN) */ ALIGN Leq: fldl y(0) jmp Lreturn Lsmall: .long 0x00000001, 0x00000000 Lbig: .long 0xffffffff, 0x7fefffff #endif