i386: move math-emu

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 470 insertions, 0 deletions

diff --git a/arch/x86/math-emu/wm_sqrt.S b/arch/x86/math-emu/wm_sqrt.S
new file mode 100644
index 000000000000..d258f59564e1
--- /dev/null
+++ b/arch/x86/math-emu/wm_sqrt.S
@@ -0,0 +1,470 @@
+        .file   "wm_sqrt.S"
+/*---------------------------------------------------------------------------+
+ |  wm_sqrt.S                                                                |
+ |                                                                           |
+ | Fixed point arithmetic square root evaluation.                            |
+ |                                                                           |
+ | Copyright (C) 1992,1993,1995,1997                                         |
+ |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
+ |                       Australia.  E-mail billm@suburbia.net               |
+ |                                                                           |
+ | Call from C as:                                                           |
+ |    int wm_sqrt(FPU_REG *n, unsigned int control_word)                     |
+ |                                                                           |
+ +---------------------------------------------------------------------------*/
+
+/*---------------------------------------------------------------------------+
+ |  wm_sqrt(FPU_REG *n, unsigned int control_word)                           |
+ |    returns the square root of n in n.                                     |
+ |                                                                           |
+ |  Use Newton's method to compute the square root of a number, which must   |
+ |  be in the range  [1.0 .. 4.0),  to 64 bits accuracy.                     |
+ |  Does not check the sign or tag of the argument.                          |
+ |  Sets the exponent, but not the sign or tag of the result.                |
+ |                                                                           |
+ |  The guess is kept in %esi:%edi                                           |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "fpu_emu.h"
+
+
+#ifndef NON_REENTRANT_FPU
+/*      Local storage on the stack: */
+#define FPU_accum_3     -4(%ebp)        /* ms word */
+#define FPU_accum_2     -8(%ebp)
+#define FPU_accum_1     -12(%ebp)
+#define FPU_accum_0     -16(%ebp)
+
+/*
+ * The de-normalised argument:
+ *                  sq_2                  sq_1              sq_0
+ *        b b b b b b b ... b b b   b b b .... b b b   b 0 0 0 ... 0
+ *           ^ binary point here
+ */
+#define FPU_fsqrt_arg_2 -20(%ebp)       /* ms word */
+#define FPU_fsqrt_arg_1 -24(%ebp)
+#define FPU_fsqrt_arg_0 -28(%ebp)       /* ls word, at most the ms bit is set */
+
+#else
+/*      Local storage in a static area: */
+.data
+        .align 4,0
+FPU_accum_3:
+        .long   0               /* ms word */
+FPU_accum_2:
+        .long   0
+FPU_accum_1:
+        .long   0
+FPU_accum_0:
+        .long   0
+
+/* The de-normalised argument:
+                    sq_2                  sq_1              sq_0
+          b b b b b b b ... b b b   b b b .... b b b   b 0 0 0 ... 0
+             ^ binary point here
+ */
+FPU_fsqrt_arg_2:
+        .long   0               /* ms word */
+FPU_fsqrt_arg_1:
+        .long   0
+FPU_fsqrt_arg_0:
+        .long   0               /* ls word, at most the ms bit is set */
+#endif /* NON_REENTRANT_FPU */ 
+
+
+.text
+ENTRY(wm_sqrt)
+        pushl   %ebp
+        movl    %esp,%ebp
+#ifndef NON_REENTRANT_FPU
+        subl    $28,%esp
+#endif /* NON_REENTRANT_FPU */
+        pushl   %esi
+        pushl   %edi
+        pushl   %ebx
+
+        movl    PARAM1,%esi
+
+        movl    SIGH(%esi),%eax
+        movl    SIGL(%esi),%ecx
+        xorl    %edx,%edx
+
+/* We use a rough linear estimate for the first guess.. */
+
+        cmpw    EXP_BIAS,EXP(%esi)
+        jnz     sqrt_arg_ge_2
+
+        shrl    $1,%eax                 /* arg is in the range  [1.0 .. 2.0) */
+        rcrl    $1,%ecx
+        rcrl    $1,%edx
+
+sqrt_arg_ge_2:
+/* From here on, n is never accessed directly again until it is
+   replaced by the answer. */
+
+        movl    %eax,FPU_fsqrt_arg_2            /* ms word of n */
+        movl    %ecx,FPU_fsqrt_arg_1
+        movl    %edx,FPU_fsqrt_arg_0
+
+/* Make a linear first estimate */
+        shrl    $1,%eax
+        addl    $0x40000000,%eax
+        movl    $0xaaaaaaaa,%ecx
+        mull    %ecx
+        shll    %edx                    /* max result was 7fff... */
+        testl   $0x80000000,%edx        /* but min was 3fff... */
+        jnz     sqrt_prelim_no_adjust
+
+        movl    $0x80000000,%edx        /* round up */
+
+sqrt_prelim_no_adjust:
+        movl    %edx,%esi       /* Our first guess */
+
+/* We have now computed (approx)   (2 + x) / 3, which forms the basis
+   for a few iterations of Newton's method */
+
+        movl    FPU_fsqrt_arg_2,%ecx    /* ms word */
+
+/*
+ * From our initial estimate, three iterations are enough to get us
+ * to 30 bits or so. This will then allow two iterations at better
+ * precision to complete the process.
+ */
+
+/* Compute  (g + n/g)/2  at each iteration (g is the guess). */
+        shrl    %ecx            /* Doing this first will prevent a divide */
+                                /* overflow later. */
+
+        movl    %ecx,%edx       /* msw of the arg / 2 */
+        divl    %esi            /* current estimate */
+        shrl    %esi            /* divide by 2 */
+        addl    %eax,%esi       /* the new estimate */
+
+        movl    %ecx,%edx
+        divl    %esi
+        shrl    %esi
+        addl    %eax,%esi
+
+        movl    %ecx,%edx
+        divl    %esi
+        shrl    %esi
+        addl    %eax,%esi
+
+/*
+ * Now that an estimate accurate to about 30 bits has been obtained (in %esi),
+ * we improve it to 60 bits or so.
+ *
+ * The strategy from now on is to compute new estimates from
+ *      guess := guess + (n - guess^2) / (2 * guess)
+ */
+
+/* First, find the square of the guess */
+        movl    %esi,%eax
+        mull    %esi
+/* guess^2 now in %edx:%eax */
+
+        movl    FPU_fsqrt_arg_1,%ecx
+        subl    %ecx,%eax
+        movl    FPU_fsqrt_arg_2,%ecx    /* ms word of normalized n */
+        sbbl    %ecx,%edx
+        jnc     sqrt_stage_2_positive
+
+/* Subtraction gives a negative result,
+   negate the result before division. */
+        notl    %edx
+        notl    %eax
+        addl    $1,%eax
+        adcl    $0,%edx
+
+        divl    %esi
+        movl    %eax,%ecx
+
+        movl    %edx,%eax
+        divl    %esi
+        jmp     sqrt_stage_2_finish
+
+sqrt_stage_2_positive:
+        divl    %esi
+        movl    %eax,%ecx
+
+        movl    %edx,%eax
+        divl    %esi
+
+        notl    %ecx
+        notl    %eax
+        addl    $1,%eax
+        adcl    $0,%ecx
+
+sqrt_stage_2_finish:
+        sarl    $1,%ecx         /* divide by 2 */
+        rcrl    $1,%eax
+
+        /* Form the new estimate in %esi:%edi */
+        movl    %eax,%edi
+        addl    %ecx,%esi
+
+        jnz     sqrt_stage_2_done       /* result should be [1..2) */
+
+#ifdef PARANOID
+/* It should be possible to get here only if the arg is ffff....ffff */
+        cmp     $0xffffffff,FPU_fsqrt_arg_1
+        jnz     sqrt_stage_2_error
+#endif /* PARANOID */
+
+/* The best rounded result. */
+        xorl    %eax,%eax
+        decl    %eax
+        movl    %eax,%edi
+        movl    %eax,%esi
+        movl    $0x7fffffff,%eax
+        jmp     sqrt_round_result
+
+#ifdef PARANOID
+sqrt_stage_2_error:
+        pushl   EX_INTERNAL|0x213
+        call    EXCEPTION
+#endif /* PARANOID */ 
+
+sqrt_stage_2_done:
+
+/* Now the square root has been computed to better than 60 bits. */
+
+/* Find the square of the guess. */
+        movl    %edi,%eax               /* ls word of guess */
+        mull    %edi
+        movl    %edx,FPU_accum_1
+
+        movl    %esi,%eax
+        mull    %esi
+        movl    %edx,FPU_accum_3
+        movl    %eax,FPU_accum_2
+
+        movl    %edi,%eax
+        mull    %esi
+        addl    %eax,FPU_accum_1
+        adcl    %edx,FPU_accum_2
+        adcl    $0,FPU_accum_3
+
+/*      movl    %esi,%eax */
+/*      mull    %edi */
+        addl    %eax,FPU_accum_1
+        adcl    %edx,FPU_accum_2
+        adcl    $0,FPU_accum_3
+
+/* guess^2 now in FPU_accum_3:FPU_accum_2:FPU_accum_1 */
+
+        movl    FPU_fsqrt_arg_0,%eax            /* get normalized n */
+        subl    %eax,FPU_accum_1
+        movl    FPU_fsqrt_arg_1,%eax
+        sbbl    %eax,FPU_accum_2
+        movl    FPU_fsqrt_arg_2,%eax            /* ms word of normalized n */
+        sbbl    %eax,FPU_accum_3
+        jnc     sqrt_stage_3_positive
+
+/* Subtraction gives a negative result,
+   negate the result before division */
+        notl    FPU_accum_1
+        notl    FPU_accum_2
+        notl    FPU_accum_3
+        addl    $1,FPU_accum_1
+        adcl    $0,FPU_accum_2
+
+#ifdef PARANOID
+        adcl    $0,FPU_accum_3  /* This must be zero */
+        jz      sqrt_stage_3_no_error
+
+sqrt_stage_3_error:
+        pushl   EX_INTERNAL|0x207
+        call    EXCEPTION
+
+sqrt_stage_3_no_error:
+#endif /* PARANOID */
+
+        movl    FPU_accum_2,%edx
+        movl    FPU_accum_1,%eax
+        divl    %esi
+        movl    %eax,%ecx
+
+        movl    %edx,%eax
+        divl    %esi
+
+        sarl    $1,%ecx         /* divide by 2 */
+        rcrl    $1,%eax
+
+        /* prepare to round the result */
+
+        addl    %ecx,%edi
+        adcl    $0,%esi
+
+        jmp     sqrt_stage_3_finished
+
+sqrt_stage_3_positive:
+        movl    FPU_accum_2,%edx
+        movl    FPU_accum_1,%eax
+        divl    %esi
+        movl    %eax,%ecx
+
+        movl    %edx,%eax
+        divl    %esi
+
+        sarl    $1,%ecx         /* divide by 2 */
+        rcrl    $1,%eax
+
+        /* prepare to round the result */
+
+        notl    %eax            /* Negate the correction term */
+        notl    %ecx
+        addl    $1,%eax
+        adcl    $0,%ecx         /* carry here ==> correction == 0 */
+        adcl    $0xffffffff,%esi
+
+        addl    %ecx,%edi
+        adcl    $0,%esi
+
+sqrt_stage_3_finished:
+
+/*
+ * The result in %esi:%edi:%esi should be good to about 90 bits here,
+ * and the rounding information here does not have sufficient accuracy
+ * in a few rare cases.
+ */
+        cmpl    $0xffffffe0,%eax
+        ja      sqrt_near_exact_x
+
+        cmpl    $0x00000020,%eax
+        jb      sqrt_near_exact
+
+        cmpl    $0x7fffffe0,%eax
+        jb      sqrt_round_result
+
+        cmpl    $0x80000020,%eax
+        jb      sqrt_get_more_precision
+
+sqrt_round_result:
+/* Set up for rounding operations */
+        movl    %eax,%edx
+        movl    %esi,%eax
+        movl    %edi,%ebx
+        movl    PARAM1,%edi
+        movw    EXP_BIAS,EXP(%edi)      /* Result is in  [1.0 .. 2.0) */
+        jmp     fpu_reg_round
+
+
+sqrt_near_exact_x:
+/* First, the estimate must be rounded up. */
+        addl    $1,%edi
+        adcl    $0,%esi
+
+sqrt_near_exact:
+/*
+ * This is an easy case because x^1/2 is monotonic.
+ * We need just find the square of our estimate, compare it
+ * with the argument, and deduce whether our estimate is
+ * above, below, or exact. We use the fact that the estimate
+ * is known to be accurate to about 90 bits.
+ */
+        movl    %edi,%eax               /* ls word of guess */
+        mull    %edi
+        movl    %edx,%ebx               /* 2nd ls word of square */
+        movl    %eax,%ecx               /* ls word of square */
+
+        movl    %edi,%eax
+        mull    %esi
+        addl    %eax,%ebx
+        addl    %eax,%ebx
+
+#ifdef PARANOID
+        cmp     $0xffffffb0,%ebx
+        jb      sqrt_near_exact_ok
+
+        cmp     $0x00000050,%ebx
+        ja      sqrt_near_exact_ok
+
+        pushl   EX_INTERNAL|0x214
+        call    EXCEPTION
+
+sqrt_near_exact_ok:
+#endif /* PARANOID */ 
+
+        or      %ebx,%ebx
+        js      sqrt_near_exact_small
+
+        jnz     sqrt_near_exact_large
+
+        or      %ebx,%edx
+        jnz     sqrt_near_exact_large
+
+/* Our estimate is exactly the right answer */
+        xorl    %eax,%eax
+        jmp     sqrt_round_result
+
+sqrt_near_exact_small:
+/* Our estimate is too small */
+        movl    $0x000000ff,%eax
+        jmp     sqrt_round_result
+        
+sqrt_near_exact_large:
+/* Our estimate is too large, we need to decrement it */
+        subl    $1,%edi
+        sbbl    $0,%esi
+        movl    $0xffffff00,%eax
+        jmp     sqrt_round_result
+
+
+sqrt_get_more_precision:
+/* This case is almost the same as the above, except we start
+   with an extra bit of precision in the estimate. */
+        stc                     /* The extra bit. */
+        rcll    $1,%edi         /* Shift the estimate left one bit */
+        rcll    $1,%esi
+
+        movl    %edi,%eax               /* ls word of guess */
+        mull    %edi
+        movl    %edx,%ebx               /* 2nd ls word of square */
+        movl    %eax,%ecx               /* ls word of square */
+
+        movl    %edi,%eax
+        mull    %esi
+        addl    %eax,%ebx
+        addl    %eax,%ebx
+
+/* Put our estimate back to its original value */
+        stc                     /* The ms bit. */
+        rcrl    $1,%esi         /* Shift the estimate left one bit */
+        rcrl    $1,%edi
+
+#ifdef PARANOID
+        cmp     $0xffffff60,%ebx
+        jb      sqrt_more_prec_ok
+
+        cmp     $0x000000a0,%ebx
+        ja      sqrt_more_prec_ok
+
+        pushl   EX_INTERNAL|0x215
+        call    EXCEPTION
+
+sqrt_more_prec_ok:
+#endif /* PARANOID */ 
+
+        or      %ebx,%ebx
+        js      sqrt_more_prec_small
+
+        jnz     sqrt_more_prec_large
+
+        or      %ebx,%ecx
+        jnz     sqrt_more_prec_large
+
+/* Our estimate is exactly the right answer */
+        movl    $0x80000000,%eax
+        jmp     sqrt_round_result
+
+sqrt_more_prec_small:
+/* Our estimate is too small */
+        movl    $0x800000ff,%eax
+        jmp     sqrt_round_result
+        
+sqrt_more_prec_large:
+/* Our estimate is too large */
+        movl    $0x7fffff00,%eax
+        jmp     sqrt_round_result