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9624c0a9e0
Coverity has identified that the __aeabi_imod function will loop forever if the denominator is not a power of 2, which is probably not the desired behaviour. The functions in the rest of the file are compiler implementations of division if ARMv7 does not implement division which is permitted by the spec. However, while most of the functions in the file are documented and referenced in other places online, __aeabi_uimod and __aeabi_imod are not. For this reason, these functions have been removed from the code base, which also removes the Coverity error. Change-Id: I20066d72365329a8b03a5536d865c4acaa2139ae Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>
156 lines
4.2 KiB
C
156 lines
4.2 KiB
C
/*
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* Copyright (c) 2017-2019, ARM Limited and Contributors. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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/*
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* Form ABI specifications:
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* int __aeabi_idiv(int numerator, int denominator);
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* unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator);
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*
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* typedef struct { int quot; int rem; } idiv_return;
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* typedef struct { unsigned quot; unsigned rem; } uidiv_return;
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*
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* __value_in_regs idiv_return __aeabi_idivmod(int numerator,
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* int *denominator);
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* __value_in_regs uidiv_return __aeabi_uidivmod(unsigned *numerator,
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* unsigned denominator);
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*/
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/* struct qr - stores quotient/remainder to handle divmod EABI interfaces. */
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struct qr {
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unsigned int q; /* computed quotient */
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unsigned int r; /* computed remainder */
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unsigned int q_n; /* specifies if quotient shall be negative */
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unsigned int r_n; /* specifies if remainder shall be negative */
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};
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static void uint_div_qr(unsigned int numerator, unsigned int denominator,
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struct qr *qr);
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/* returns in R0 and R1 by tail calling an asm function */
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unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator);
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unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator);
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/* returns in R0 and R1 by tail calling an asm function */
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signed int __aeabi_idivmod(signed int numerator, signed int denominator);
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signed int __aeabi_idiv(signed int numerator, signed int denominator);
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/*
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* __ste_idivmod_ret_t __aeabi_idivmod(signed numerator, signed denominator)
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* Numerator and Denominator are received in R0 and R1.
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* Where __ste_idivmod_ret_t is returned in R0 and R1.
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*
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* __ste_uidivmod_ret_t __aeabi_uidivmod(unsigned numerator,
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* unsigned denominator)
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* Numerator and Denominator are received in R0 and R1.
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* Where __ste_uidivmod_ret_t is returned in R0 and R1.
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*/
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#ifdef __GNUC__
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signed int ret_idivmod_values(signed int quotient, signed int remainder);
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unsigned int ret_uidivmod_values(unsigned int quotient, unsigned int remainder);
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#else
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#error "Compiler not supported"
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#endif
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static void division_qr(unsigned int n, unsigned int p, struct qr *qr)
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{
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unsigned int i = 1, q = 0;
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if (p == 0) {
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qr->r = 0xFFFFFFFF; /* division by 0 */
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return;
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}
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while ((p >> 31) == 0) {
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i = i << 1; /* count the max division steps */
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p = p << 1; /* increase p until it has maximum size*/
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}
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while (i > 0) {
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q = q << 1; /* write bit in q at index (size-1) */
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if (n >= p) {
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n -= p;
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q++;
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}
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p = p >> 1; /* decrease p */
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i = i >> 1; /* decrease remaining size in q */
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}
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qr->r = n;
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qr->q = q;
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}
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static void uint_div_qr(unsigned int numerator, unsigned int denominator,
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struct qr *qr)
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{
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division_qr(numerator, denominator, qr);
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/* negate quotient and/or remainder according to requester */
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if (qr->q_n)
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qr->q = -qr->q;
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if (qr->r_n)
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qr->r = -qr->r;
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}
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unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator)
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{
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struct qr qr = { .q_n = 0, .r_n = 0 };
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uint_div_qr(numerator, denominator, &qr);
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return qr.q;
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}
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unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator)
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{
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struct qr qr = { .q_n = 0, .r_n = 0 };
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uint_div_qr(numerator, denominator, &qr);
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return ret_uidivmod_values(qr.q, qr.r);
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}
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signed int __aeabi_idiv(signed int numerator, signed int denominator)
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{
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struct qr qr = { .q_n = 0, .r_n = 0 };
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if (((numerator < 0) && (denominator > 0)) ||
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((numerator > 0) && (denominator < 0)))
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qr.q_n = 1; /* quotient shall be negate */
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if (numerator < 0) {
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numerator = -numerator;
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qr.r_n = 1; /* remainder shall be negate */
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}
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if (denominator < 0)
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denominator = -denominator;
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uint_div_qr(numerator, denominator, &qr);
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return qr.q;
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}
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signed int __aeabi_idivmod(signed int numerator, signed int denominator)
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{
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struct qr qr = { .q_n = 0, .r_n = 0 };
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if (((numerator < 0) && (denominator > 0)) ||
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((numerator > 0) && (denominator < 0)))
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qr.q_n = 1; /* quotient shall be negate */
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if (numerator < 0) {
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numerator = -numerator;
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qr.r_n = 1; /* remainder shall be negate */
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}
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if (denominator < 0)
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denominator = -denominator;
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uint_div_qr(numerator, denominator, &qr);
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return ret_idivmod_values(qr.q, qr.r);
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}
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