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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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bd6be579a7
Functions in math-emu are annotated as ENTRY() symbols, but their
ends are not annotated at all. But these are standard functions
called from C, with proper stack register update etc.
Omitting the ends means:
* the annotations are not paired and we cannot deal with such functions
e.g. in objtool
* the symbols are not marked as functions in the object file
* there are no sizes of the functions in the object file
So fix this by adding ENDPROC() to each such case in math-emu.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170824080624.7768-1-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
471 lines
11 KiB
ArmAsm
471 lines
11 KiB
ArmAsm
.file "wm_sqrt.S"
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/*---------------------------------------------------------------------------+
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| wm_sqrt.S |
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| Fixed point arithmetic square root evaluation. |
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| Copyright (C) 1992,1993,1995,1997 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
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| Australia. E-mail billm@suburbia.net |
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| Call from C as: |
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| int wm_sqrt(FPU_REG *n, unsigned int control_word) |
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+---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------+
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| wm_sqrt(FPU_REG *n, unsigned int control_word) |
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| returns the square root of n in n. |
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| Use Newton's method to compute the square root of a number, which must |
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| be in the range [1.0 .. 4.0), to 64 bits accuracy. |
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| Does not check the sign or tag of the argument. |
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| Sets the exponent, but not the sign or tag of the result. |
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| The guess is kept in %esi:%edi |
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+---------------------------------------------------------------------------*/
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#include "exception.h"
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#include "fpu_emu.h"
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#ifndef NON_REENTRANT_FPU
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/* Local storage on the stack: */
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#define FPU_accum_3 -4(%ebp) /* ms word */
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#define FPU_accum_2 -8(%ebp)
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#define FPU_accum_1 -12(%ebp)
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#define FPU_accum_0 -16(%ebp)
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/*
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* The de-normalised argument:
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* sq_2 sq_1 sq_0
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* b b b b b b b ... b b b b b b .... b b b b 0 0 0 ... 0
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* ^ binary point here
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*/
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#define FPU_fsqrt_arg_2 -20(%ebp) /* ms word */
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#define FPU_fsqrt_arg_1 -24(%ebp)
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#define FPU_fsqrt_arg_0 -28(%ebp) /* ls word, at most the ms bit is set */
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#else
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/* Local storage in a static area: */
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.data
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.align 4,0
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FPU_accum_3:
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.long 0 /* ms word */
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FPU_accum_2:
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.long 0
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FPU_accum_1:
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.long 0
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FPU_accum_0:
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.long 0
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/* The de-normalised argument:
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sq_2 sq_1 sq_0
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b b b b b b b ... b b b b b b .... b b b b 0 0 0 ... 0
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^ binary point here
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*/
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FPU_fsqrt_arg_2:
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.long 0 /* ms word */
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FPU_fsqrt_arg_1:
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.long 0
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FPU_fsqrt_arg_0:
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.long 0 /* ls word, at most the ms bit is set */
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#endif /* NON_REENTRANT_FPU */
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.text
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ENTRY(wm_sqrt)
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pushl %ebp
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movl %esp,%ebp
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#ifndef NON_REENTRANT_FPU
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subl $28,%esp
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#endif /* NON_REENTRANT_FPU */
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pushl %esi
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pushl %edi
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pushl %ebx
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movl PARAM1,%esi
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movl SIGH(%esi),%eax
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movl SIGL(%esi),%ecx
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xorl %edx,%edx
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/* We use a rough linear estimate for the first guess.. */
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cmpw EXP_BIAS,EXP(%esi)
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jnz sqrt_arg_ge_2
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shrl $1,%eax /* arg is in the range [1.0 .. 2.0) */
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rcrl $1,%ecx
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rcrl $1,%edx
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sqrt_arg_ge_2:
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/* From here on, n is never accessed directly again until it is
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replaced by the answer. */
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movl %eax,FPU_fsqrt_arg_2 /* ms word of n */
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movl %ecx,FPU_fsqrt_arg_1
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movl %edx,FPU_fsqrt_arg_0
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/* Make a linear first estimate */
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shrl $1,%eax
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addl $0x40000000,%eax
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movl $0xaaaaaaaa,%ecx
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mull %ecx
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shll %edx /* max result was 7fff... */
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testl $0x80000000,%edx /* but min was 3fff... */
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jnz sqrt_prelim_no_adjust
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movl $0x80000000,%edx /* round up */
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sqrt_prelim_no_adjust:
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movl %edx,%esi /* Our first guess */
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/* We have now computed (approx) (2 + x) / 3, which forms the basis
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for a few iterations of Newton's method */
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movl FPU_fsqrt_arg_2,%ecx /* ms word */
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/*
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* From our initial estimate, three iterations are enough to get us
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* to 30 bits or so. This will then allow two iterations at better
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* precision to complete the process.
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*/
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/* Compute (g + n/g)/2 at each iteration (g is the guess). */
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shrl %ecx /* Doing this first will prevent a divide */
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/* overflow later. */
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movl %ecx,%edx /* msw of the arg / 2 */
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divl %esi /* current estimate */
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shrl %esi /* divide by 2 */
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addl %eax,%esi /* the new estimate */
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movl %ecx,%edx
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divl %esi
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shrl %esi
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addl %eax,%esi
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movl %ecx,%edx
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divl %esi
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shrl %esi
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addl %eax,%esi
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/*
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* Now that an estimate accurate to about 30 bits has been obtained (in %esi),
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* we improve it to 60 bits or so.
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*
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* The strategy from now on is to compute new estimates from
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* guess := guess + (n - guess^2) / (2 * guess)
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*/
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/* First, find the square of the guess */
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movl %esi,%eax
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mull %esi
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/* guess^2 now in %edx:%eax */
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movl FPU_fsqrt_arg_1,%ecx
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subl %ecx,%eax
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movl FPU_fsqrt_arg_2,%ecx /* ms word of normalized n */
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sbbl %ecx,%edx
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jnc sqrt_stage_2_positive
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/* Subtraction gives a negative result,
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negate the result before division. */
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notl %edx
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notl %eax
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addl $1,%eax
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adcl $0,%edx
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divl %esi
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movl %eax,%ecx
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movl %edx,%eax
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divl %esi
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jmp sqrt_stage_2_finish
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sqrt_stage_2_positive:
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divl %esi
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movl %eax,%ecx
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movl %edx,%eax
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divl %esi
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notl %ecx
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notl %eax
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addl $1,%eax
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adcl $0,%ecx
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sqrt_stage_2_finish:
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sarl $1,%ecx /* divide by 2 */
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rcrl $1,%eax
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/* Form the new estimate in %esi:%edi */
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movl %eax,%edi
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addl %ecx,%esi
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jnz sqrt_stage_2_done /* result should be [1..2) */
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#ifdef PARANOID
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/* It should be possible to get here only if the arg is ffff....ffff */
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cmp $0xffffffff,FPU_fsqrt_arg_1
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jnz sqrt_stage_2_error
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#endif /* PARANOID */
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/* The best rounded result. */
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xorl %eax,%eax
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decl %eax
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movl %eax,%edi
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movl %eax,%esi
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movl $0x7fffffff,%eax
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jmp sqrt_round_result
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#ifdef PARANOID
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sqrt_stage_2_error:
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pushl EX_INTERNAL|0x213
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call EXCEPTION
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#endif /* PARANOID */
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sqrt_stage_2_done:
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/* Now the square root has been computed to better than 60 bits. */
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/* Find the square of the guess. */
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movl %edi,%eax /* ls word of guess */
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mull %edi
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movl %edx,FPU_accum_1
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movl %esi,%eax
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mull %esi
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movl %edx,FPU_accum_3
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movl %eax,FPU_accum_2
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movl %edi,%eax
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mull %esi
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addl %eax,FPU_accum_1
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adcl %edx,FPU_accum_2
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adcl $0,FPU_accum_3
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/* movl %esi,%eax */
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/* mull %edi */
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addl %eax,FPU_accum_1
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adcl %edx,FPU_accum_2
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adcl $0,FPU_accum_3
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/* guess^2 now in FPU_accum_3:FPU_accum_2:FPU_accum_1 */
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movl FPU_fsqrt_arg_0,%eax /* get normalized n */
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subl %eax,FPU_accum_1
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movl FPU_fsqrt_arg_1,%eax
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sbbl %eax,FPU_accum_2
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movl FPU_fsqrt_arg_2,%eax /* ms word of normalized n */
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sbbl %eax,FPU_accum_3
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jnc sqrt_stage_3_positive
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/* Subtraction gives a negative result,
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negate the result before division */
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notl FPU_accum_1
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notl FPU_accum_2
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notl FPU_accum_3
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addl $1,FPU_accum_1
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adcl $0,FPU_accum_2
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#ifdef PARANOID
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adcl $0,FPU_accum_3 /* This must be zero */
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jz sqrt_stage_3_no_error
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sqrt_stage_3_error:
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pushl EX_INTERNAL|0x207
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call EXCEPTION
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sqrt_stage_3_no_error:
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#endif /* PARANOID */
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movl FPU_accum_2,%edx
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movl FPU_accum_1,%eax
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divl %esi
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movl %eax,%ecx
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movl %edx,%eax
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divl %esi
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sarl $1,%ecx /* divide by 2 */
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rcrl $1,%eax
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/* prepare to round the result */
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addl %ecx,%edi
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adcl $0,%esi
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jmp sqrt_stage_3_finished
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sqrt_stage_3_positive:
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movl FPU_accum_2,%edx
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movl FPU_accum_1,%eax
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divl %esi
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movl %eax,%ecx
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movl %edx,%eax
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divl %esi
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sarl $1,%ecx /* divide by 2 */
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rcrl $1,%eax
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/* prepare to round the result */
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notl %eax /* Negate the correction term */
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notl %ecx
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addl $1,%eax
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adcl $0,%ecx /* carry here ==> correction == 0 */
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adcl $0xffffffff,%esi
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addl %ecx,%edi
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adcl $0,%esi
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sqrt_stage_3_finished:
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/*
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* The result in %esi:%edi:%esi should be good to about 90 bits here,
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* and the rounding information here does not have sufficient accuracy
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* in a few rare cases.
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*/
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cmpl $0xffffffe0,%eax
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ja sqrt_near_exact_x
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cmpl $0x00000020,%eax
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jb sqrt_near_exact
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cmpl $0x7fffffe0,%eax
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jb sqrt_round_result
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cmpl $0x80000020,%eax
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jb sqrt_get_more_precision
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sqrt_round_result:
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/* Set up for rounding operations */
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movl %eax,%edx
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movl %esi,%eax
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movl %edi,%ebx
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movl PARAM1,%edi
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movw EXP_BIAS,EXP(%edi) /* Result is in [1.0 .. 2.0) */
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jmp fpu_reg_round
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sqrt_near_exact_x:
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/* First, the estimate must be rounded up. */
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addl $1,%edi
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adcl $0,%esi
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sqrt_near_exact:
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/*
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* This is an easy case because x^1/2 is monotonic.
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* We need just find the square of our estimate, compare it
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* with the argument, and deduce whether our estimate is
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* above, below, or exact. We use the fact that the estimate
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* is known to be accurate to about 90 bits.
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*/
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movl %edi,%eax /* ls word of guess */
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mull %edi
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movl %edx,%ebx /* 2nd ls word of square */
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movl %eax,%ecx /* ls word of square */
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movl %edi,%eax
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mull %esi
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addl %eax,%ebx
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addl %eax,%ebx
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#ifdef PARANOID
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cmp $0xffffffb0,%ebx
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jb sqrt_near_exact_ok
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cmp $0x00000050,%ebx
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ja sqrt_near_exact_ok
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pushl EX_INTERNAL|0x214
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call EXCEPTION
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sqrt_near_exact_ok:
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#endif /* PARANOID */
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or %ebx,%ebx
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js sqrt_near_exact_small
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jnz sqrt_near_exact_large
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or %ebx,%edx
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jnz sqrt_near_exact_large
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/* Our estimate is exactly the right answer */
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xorl %eax,%eax
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jmp sqrt_round_result
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sqrt_near_exact_small:
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/* Our estimate is too small */
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movl $0x000000ff,%eax
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jmp sqrt_round_result
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sqrt_near_exact_large:
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/* Our estimate is too large, we need to decrement it */
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subl $1,%edi
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sbbl $0,%esi
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movl $0xffffff00,%eax
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jmp sqrt_round_result
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sqrt_get_more_precision:
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/* This case is almost the same as the above, except we start
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with an extra bit of precision in the estimate. */
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stc /* The extra bit. */
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rcll $1,%edi /* Shift the estimate left one bit */
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rcll $1,%esi
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movl %edi,%eax /* ls word of guess */
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mull %edi
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movl %edx,%ebx /* 2nd ls word of square */
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movl %eax,%ecx /* ls word of square */
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movl %edi,%eax
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mull %esi
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addl %eax,%ebx
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addl %eax,%ebx
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/* Put our estimate back to its original value */
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stc /* The ms bit. */
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rcrl $1,%esi /* Shift the estimate left one bit */
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rcrl $1,%edi
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#ifdef PARANOID
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cmp $0xffffff60,%ebx
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jb sqrt_more_prec_ok
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cmp $0x000000a0,%ebx
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ja sqrt_more_prec_ok
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pushl EX_INTERNAL|0x215
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call EXCEPTION
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sqrt_more_prec_ok:
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#endif /* PARANOID */
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or %ebx,%ebx
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js sqrt_more_prec_small
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jnz sqrt_more_prec_large
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or %ebx,%ecx
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jnz sqrt_more_prec_large
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/* Our estimate is exactly the right answer */
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movl $0x80000000,%eax
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jmp sqrt_round_result
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sqrt_more_prec_small:
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/* Our estimate is too small */
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movl $0x800000ff,%eax
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jmp sqrt_round_result
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sqrt_more_prec_large:
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/* Our estimate is too large */
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movl $0x7fffff00,%eax
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jmp sqrt_round_result
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ENDPROC(wm_sqrt)
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