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780813d701
The third argument of div_Xsig() is the output of the division, but is marked
'const', which means the compiler is not expecting it to be updated and may
generate bad code around the call. clang-21 now warns about the pattern since
an uninitialized variable is passed into two 'const' arguments by reference:
arch/x86/math-emu/poly_atan.c:93:28: error: variable 'argSignif' is uninitialized \
when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
93 | div_Xsig(&Numer, &Denom, &argSignif);
| ^~~~~~~~~
arch/x86/math-emu/poly_l2.c:195:29: error: variable 'argSignif' is uninitialized \
when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
195 | div_Xsig(&Numer, &Denom, &argSignif);
| ^~~~~~~~~
The implementation is in assembly, so the problem has gone unnoticed since the
code was added in the linux-1.1 days. Remove the 'const' marker here.
Fixes: e19a1bdb835c ("Import 1.1.38")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20250807205334.123231-1-arnd@kernel.org
116 lines
4.6 KiB
C
116 lines
4.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*---------------------------------------------------------------------------+
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| poly.h |
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| Header file for the FPU-emu poly*.c source files. |
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| Copyright (C) 1994,1999 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
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| Australia. E-mail billm@melbpc.org.au |
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| Declarations and definitions for functions operating on Xsig (12-byte |
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| extended-significand) quantities. |
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+---------------------------------------------------------------------------*/
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#ifndef _POLY_H
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#define _POLY_H
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/* This 12-byte structure is used to improve the accuracy of computation
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of transcendental functions.
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Intended to be used to get results better than 8-byte computation
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allows. 9-byte would probably be sufficient.
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*/
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typedef struct {
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unsigned long lsw;
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unsigned long midw;
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unsigned long msw;
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} Xsig;
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asmlinkage void mul64(unsigned long long const *a, unsigned long long const *b,
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unsigned long long *result);
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asmlinkage void polynomial_Xsig(Xsig *, const unsigned long long *x,
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const unsigned long long terms[], const int n);
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asmlinkage void mul32_Xsig(Xsig *, const unsigned long mult);
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asmlinkage void mul64_Xsig(Xsig *, const unsigned long long *mult);
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asmlinkage void mul_Xsig_Xsig(Xsig *dest, const Xsig *mult);
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asmlinkage void shr_Xsig(Xsig *, const int n);
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asmlinkage int round_Xsig(Xsig *);
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asmlinkage int norm_Xsig(Xsig *);
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asmlinkage void div_Xsig(Xsig *x1, const Xsig *x2, Xsig *dest);
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/* Macro to extract the most significant 32 bits from a long long */
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#define LL_MSW(x) (((unsigned long *)&x)[1])
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/* Macro to initialize an Xsig struct */
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#define MK_XSIG(a,b,c) { c, b, a }
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/* Macro to access the 8 ms bytes of an Xsig as a long long */
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#define XSIG_LL(x) (*(unsigned long long *)&x.midw)
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/*
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Need to run gcc with optimizations on to get these to
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actually be in-line.
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*/
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/* Multiply two fixed-point 32 bit numbers, producing a 32 bit result.
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The answer is the ms word of the product. */
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/* Some versions of gcc make it difficult to stop eax from being clobbered.
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Merely specifying that it is used doesn't work...
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*/
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static inline unsigned long mul_32_32(const unsigned long arg1,
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const unsigned long arg2)
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{
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int retval;
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asm volatile ("mull %2; movl %%edx,%%eax":"=a" (retval)
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:"0"(arg1), "g"(arg2)
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:"dx");
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return retval;
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}
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/* Add the 12 byte Xsig x2 to Xsig dest, with no checks for overflow. */
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static inline void add_Xsig_Xsig(Xsig *dest, const Xsig *x2)
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{
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asm volatile ("movl %1,%%edi; movl %2,%%esi;\n"
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"movl (%%esi),%%eax; addl %%eax,(%%edi);\n"
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"movl 4(%%esi),%%eax; adcl %%eax,4(%%edi);\n"
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"movl 8(%%esi),%%eax; adcl %%eax,8(%%edi);\n":"=g"
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(*dest):"g"(dest), "g"(x2)
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:"ax", "si", "di");
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}
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/* Add the 12 byte Xsig x2 to Xsig dest, adjust exp if overflow occurs. */
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/* Note: the constraints in the asm statement didn't always work properly
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with gcc 2.5.8. Changing from using edi to using ecx got around the
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problem, but keep fingers crossed! */
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static inline void add_two_Xsig(Xsig *dest, const Xsig *x2, long int *exp)
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{
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asm volatile ("movl %2,%%ecx; movl %3,%%esi;\n"
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"movl (%%esi),%%eax; addl %%eax,(%%ecx);\n"
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"movl 4(%%esi),%%eax; adcl %%eax,4(%%ecx);\n"
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"movl 8(%%esi),%%eax; adcl %%eax,8(%%ecx);\n"
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"jnc 0f;\n"
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"rcrl 8(%%ecx); rcrl 4(%%ecx); rcrl (%%ecx)\n"
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"movl %4,%%ecx; incl (%%ecx)\n"
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"movl $1,%%eax; jmp 1f;\n"
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"0: xorl %%eax,%%eax;\n" "1:\n":"=g" (*exp), "=g"(*dest)
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:"g"(dest), "g"(x2), "g"(exp)
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:"cx", "si", "ax");
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}
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/* Negate (subtract from 1.0) the 12 byte Xsig */
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/* This is faster in a loop on my 386 than using the "neg" instruction. */
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static inline void negate_Xsig(Xsig *x)
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{
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asm volatile ("movl %1,%%esi;\n"
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"xorl %%ecx,%%ecx;\n"
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"movl %%ecx,%%eax; subl (%%esi),%%eax; movl %%eax,(%%esi);\n"
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"movl %%ecx,%%eax; sbbl 4(%%esi),%%eax; movl %%eax,4(%%esi);\n"
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"movl %%ecx,%%eax; sbbl 8(%%esi),%%eax; movl %%eax,8(%%esi);\n":"=g"
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(*x):"g"(x):"si", "ax", "cx");
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}
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#endif /* _POLY_H */
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