xtensa: add helpers for division, remainder and shifts

Don't rely on libgcc presence, build own versions of the helpers with
correct ABI.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/include/asm/asmmacro.h

@@ -191,6 +191,40 @@
 #endif
 	.endm
 
+	.macro	do_nsau cnt, val, tmp, a
+#if XCHAL_HAVE_NSA
+	nsau	\cnt, \val
+#else
+	mov	\a, \val
+	movi	\cnt, 0
+	extui	\tmp, \a, 16, 16
+	bnez	\tmp, 0f
+	movi	\cnt, 16
+	slli	\a, \a, 16
+0:
+	extui	\tmp, \a, 24, 8
+	bnez	\tmp, 1f
+	addi	\cnt, \cnt, 8
+	slli	\a, \a, 8
+1:
+	movi	\tmp, __nsau_data
+	extui	\a, \a, 24, 8
+	add	\tmp, \tmp, \a
+	l8ui	\tmp, \tmp, 0
+	add	\cnt, \cnt, \tmp
+#endif /* !XCHAL_HAVE_NSA */
+	.endm
+
+	.macro	do_abs dst, src, tmp
+#if XCHAL_HAVE_ABS
+	abs	\dst, \src
+#else
+	neg	\tmp, \src
+	movgez	\tmp, \src, \src
+	mov	\dst, \tmp
+#endif
+	.endm
+
 #define XTENSA_STACK_ALIGNMENT		16
 
 #if defined(__XTENSA_WINDOWED_ABI__)

arch/xtensa/lib/Makefile

@@ -4,5 +4,7 @@
 #
 
 lib-y	+= memcopy.o memset.o checksum.o \
+	   ashldi3.o ashrdi3.o lshrdi3.o \
+	   divsi3.o udivsi3.o modsi3.o umodsi3.o mulsi3.o \
 	   usercopy.o strncpy_user.o strnlen_user.o
 lib-$(CONFIG_PCI) += pci-auto.o

arch/xtensa/lib/ashldi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+#ifdef __XTENSA_EB__
+#define uh a2
+#define ul a3
+#else
+#define uh a3
+#define ul a2
+#endif /* __XTENSA_EB__ */
+
+ENTRY(__ashldi3)
+
+	abi_entry_default
+	ssl	a4
+	bgei	a4, 32, .Llow_only
+	src	uh, uh, ul
+	sll	ul, ul
+	abi_ret_default
+
+.Llow_only:
+	sll	uh, ul
+	movi	ul, 0
+	abi_ret_default
+
+ENDPROC(__ashldi3)

arch/xtensa/lib/ashrdi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+#ifdef __XTENSA_EB__
+#define uh a2
+#define ul a3
+#else
+#define uh a3
+#define ul a2
+#endif /* __XTENSA_EB__ */
+
+ENTRY(__ashrdi3)
+
+	abi_entry_default
+	ssr	a4
+	bgei	a4, 32, .Lhigh_only
+	src	ul, uh, ul
+	sra	uh, uh
+	abi_ret_default
+
+.Lhigh_only:
+	sra	ul, uh
+	srai	uh, uh, 31
+	abi_ret_default
+
+ENDPROC(__ashrdi3)

arch/xtensa/lib/divsi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+ENTRY(__divsi3)
+
+	abi_entry_default
+#if XCHAL_HAVE_DIV32
+	quos	a2, a2, a3
+#else
+	xor	a7, a2, a3	/* sign = dividend ^ divisor */
+	do_abs	a6, a2, a4	/* udividend = abs (dividend) */
+	do_abs	a3, a3, a4	/* udivisor = abs (divisor) */
+	bltui	a3, 2, .Lle_one	/* check if udivisor <= 1 */
+	do_nsau	a5, a6, a2, a8	/* udividend_shift = nsau (udividend) */
+	do_nsau	a4, a3, a2, a8	/* udivisor_shift = nsau (udivisor) */
+	bgeu	a5, a4, .Lspecial
+
+	sub	a4, a4, a5	/* count = udivisor_shift - udividend_shift */
+	ssl	a4
+	sll	a3, a3		/* udivisor <<= count */
+	movi	a2, 0		/* quotient = 0 */
+
+	/* test-subtract-and-shift loop; one quotient bit on each iteration */
+#if XCHAL_HAVE_LOOPS
+	loopnez	a4, .Lloopend
+#endif /* XCHAL_HAVE_LOOPS */
+.Lloop:
+	bltu	a6, a3, .Lzerobit
+	sub	a6, a6, a3
+	addi	a2, a2, 1
+.Lzerobit:
+	slli	a2, a2, 1
+	srli	a3, a3, 1
+#if !XCHAL_HAVE_LOOPS
+	addi	a4, a4, -1
+	bnez	a4, .Lloop
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lloopend:
+
+	bltu	a6, a3, .Lreturn
+	addi	a2, a2, 1	/* increment if udividend >= udivisor */
+.Lreturn:
+	neg	a5, a2
+	movltz	a2, a5, a7	/* return (sign < 0) ? -quotient : quotient */
+	abi_ret_default
+
+.Lle_one:
+	beqz	a3, .Lerror
+	neg	a2, a6		/* if udivisor == 1, then return... */
+	movgez	a2, a6, a7	/* (sign < 0) ? -udividend : udividend */
+	abi_ret_default
+
+.Lspecial:
+	bltu	a6, a3, .Lreturn0 /* if dividend < divisor, return 0 */
+	movi	a2, 1
+	movi	a4, -1
+	movltz	a2, a4, a7	/* else return (sign < 0) ? -1 : 1 */
+	abi_ret_default
+
+.Lerror:
+	/* Divide by zero: Use an illegal instruction to force an exception.
+	   The subsequent "DIV0" string can be recognized by the exception
+	   handler to identify the real cause of the exception.  */
+	ill
+	.ascii	"DIV0"
+
+.Lreturn0:
+	movi	a2, 0
+#endif /* XCHAL_HAVE_DIV32 */
+	abi_ret_default
+
+ENDPROC(__divsi3)

arch/xtensa/lib/lshrdi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+#ifdef __XTENSA_EB__
+#define uh a2
+#define ul a3
+#else
+#define uh a3
+#define ul a2
+#endif /* __XTENSA_EB__ */
+
+ENTRY(__lshrdi3)
+
+	abi_entry_default
+	ssr	a4
+	bgei	a4, 32, .Lhigh_only
+	src	ul, uh, ul
+	srl	uh, uh
+	abi_ret_default
+
+.Lhigh_only:
+	srl	ul, uh
+	movi	uh, 0
+	abi_ret_default
+
+ENDPROC(__lshrdi3)

arch/xtensa/lib/modsi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+ENTRY(__modsi3)
+
+	abi_entry_default
+#if XCHAL_HAVE_DIV32
+	rems	a2, a2, a3
+#else
+	mov	a7, a2		/* save original (signed) dividend */
+	do_abs	a2, a2, a4	/* udividend = abs (dividend) */
+	do_abs	a3, a3, a4	/* udivisor = abs (divisor) */
+	bltui	a3, 2, .Lle_one	/* check if udivisor <= 1 */
+	do_nsau	a5, a2, a6, a8	/* udividend_shift = nsau (udividend) */
+	do_nsau	a4, a3, a6, a8	/* udivisor_shift = nsau (udivisor) */
+	bgeu	a5, a4, .Lspecial
+
+	sub	a4, a4, a5	/* count = udivisor_shift - udividend_shift */
+	ssl	a4
+	sll	a3, a3		/* udivisor <<= count */
+
+	/* test-subtract-and-shift loop */
+#if XCHAL_HAVE_LOOPS
+	loopnez	a4, .Lloopend
+#endif /* XCHAL_HAVE_LOOPS */
+.Lloop:
+	bltu	a2, a3, .Lzerobit
+	sub	a2, a2, a3
+.Lzerobit:
+	srli	a3, a3, 1
+#if !XCHAL_HAVE_LOOPS
+	addi	a4, a4, -1
+	bnez	a4, .Lloop
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lloopend:
+
+.Lspecial:
+	bltu	a2, a3, .Lreturn
+	sub	a2, a2, a3	/* subtract again if udividend >= udivisor */
+.Lreturn:
+	bgez	a7, .Lpositive
+	neg	a2, a2		/* if (dividend < 0), return -udividend */
+.Lpositive:
+	abi_ret_default
+
+.Lle_one:
+	bnez	a3, .Lreturn0
+
+	/* Divide by zero: Use an illegal instruction to force an exception.
+	   The subsequent "DIV0" string can be recognized by the exception
+	   handler to identify the real cause of the exception.  */
+	ill
+	.ascii	"DIV0"
+
+.Lreturn0:
+	movi	a2, 0
+#endif /* XCHAL_HAVE_DIV32 */
+	abi_ret_default
+
+ENDPROC(__modsi3)
+
+#if !XCHAL_HAVE_NSA
+	.section .rodata
+	.align	4
+	.global	__nsau_data
+	.type	__nsau_data, @object
+__nsau_data:
+	.byte	8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4
+	.byte	3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3
+	.byte	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
+	.byte	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
+	.byte	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
+	.byte	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
+	.byte	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
+	.byte	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.byte	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	.size	__nsau_data, . - __nsau_data
+#endif /* !XCHAL_HAVE_NSA */

arch/xtensa/lib/mulsi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+	.macro	do_addx2 dst, as, at, tmp
+#if XCHAL_HAVE_ADDX
+	addx2	\dst, \as, \at
+#else
+	slli	\tmp, \as, 1
+	add	\dst, \tmp, \at
+#endif
+	.endm
+
+	.macro	do_addx4 dst, as, at, tmp
+#if XCHAL_HAVE_ADDX
+	addx4	\dst, \as, \at
+#else
+	slli	\tmp, \as, 2
+	add	\dst, \tmp, \at
+#endif
+	.endm
+
+	.macro	do_addx8 dst, as, at, tmp
+#if XCHAL_HAVE_ADDX
+	addx8	\dst, \as, \at
+#else
+	slli	\tmp, \as, 3
+	add	\dst, \tmp, \at
+#endif
+	.endm
+
+ENTRY(__mulsi3)
+
+	abi_entry_default
+
+#if XCHAL_HAVE_MUL32
+	mull	a2, a2, a3
+
+#elif XCHAL_HAVE_MUL16
+	or	a4, a2, a3
+	srai	a4, a4, 16
+	bnez	a4, .LMUL16
+	mul16u	a2, a2, a3
+	abi_ret_default
+.LMUL16:
+	srai	a4, a2, 16
+	srai	a5, a3, 16
+	mul16u	a7, a4, a3
+	mul16u	a6, a5, a2
+	mul16u	a4, a2, a3
+	add	a7, a7, a6
+	slli	a7, a7, 16
+	add	a2, a7, a4
+
+#elif XCHAL_HAVE_MAC16
+	mul.aa.hl a2, a3
+	mula.aa.lh a2, a3
+	rsr	a5, ACCLO
+	umul.aa.ll a2, a3
+	rsr	a4, ACCLO
+	slli	a5, a5, 16
+	add	a2, a4, a5
+
+#else /* !MUL32 && !MUL16 && !MAC16 */
+
+	/* Multiply one bit at a time, but unroll the loop 4x to better
+	   exploit the addx instructions and avoid overhead.
+	   Peel the first iteration to save a cycle on init.  */
+
+	/* Avoid negative numbers.  */
+	xor	a5, a2, a3	/* Top bit is 1 if one input is negative.  */
+	do_abs	a3, a3, a6
+	do_abs	a2, a2, a6
+
+	/* Swap so the second argument is smaller.  */
+	sub	a7, a2, a3
+	mov	a4, a3
+	movgez	a4, a2, a7	/* a4 = max (a2, a3) */
+	movltz	a3, a2, a7	/* a3 = min (a2, a3) */
+
+	movi	a2, 0
+	extui	a6, a3, 0, 1
+	movnez	a2, a4, a6
+
+	do_addx2 a7, a4, a2, a7
+	extui	a6, a3, 1, 1
+	movnez	a2, a7, a6
+
+	do_addx4 a7, a4, a2, a7
+	extui	a6, a3, 2, 1
+	movnez	a2, a7, a6
+
+	do_addx8 a7, a4, a2, a7
+	extui	a6, a3, 3, 1
+	movnez	a2, a7, a6
+
+	bgeui	a3, 16, .Lmult_main_loop
+	neg	a3, a2
+	movltz	a2, a3, a5
+	abi_ret_default
+
+	.align	4
+.Lmult_main_loop:
+	srli	a3, a3, 4
+	slli	a4, a4, 4
+
+	add	a7, a4, a2
+	extui	a6, a3, 0, 1
+	movnez	a2, a7, a6
+
+	do_addx2 a7, a4, a2, a7
+	extui	a6, a3, 1, 1
+	movnez	a2, a7, a6
+
+	do_addx4 a7, a4, a2, a7
+	extui	a6, a3, 2, 1
+	movnez	a2, a7, a6
+
+	do_addx8 a7, a4, a2, a7
+	extui	a6, a3, 3, 1
+	movnez	a2, a7, a6
+
+	bgeui	a3, 16, .Lmult_main_loop
+
+	neg	a3, a2
+	movltz	a2, a3, a5
+
+#endif /* !MUL32 && !MUL16 && !MAC16 */
+
+	abi_ret_default
+
+ENDPROC(__mulsi3)

arch/xtensa/lib/udivsi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+ENTRY(__udivsi3)
+
+	abi_entry_default
+#if XCHAL_HAVE_DIV32
+	quou	a2, a2, a3
+#else
+	bltui	a3, 2, .Lle_one	/* check if the divisor <= 1 */
+
+	mov	a6, a2		/* keep dividend in a6 */
+	do_nsau	a5, a6, a2, a7	/* dividend_shift = nsau (dividend) */
+	do_nsau	a4, a3, a2, a7	/* divisor_shift = nsau (divisor) */
+	bgeu	a5, a4, .Lspecial
+
+	sub	a4, a4, a5	/* count = divisor_shift - dividend_shift */
+	ssl	a4
+	sll	a3, a3		/* divisor <<= count */
+	movi	a2, 0		/* quotient = 0 */
+
+	/* test-subtract-and-shift loop; one quotient bit on each iteration */
+#if XCHAL_HAVE_LOOPS
+	loopnez	a4, .Lloopend
+#endif /* XCHAL_HAVE_LOOPS */
+.Lloop:
+	bltu	a6, a3, .Lzerobit
+	sub	a6, a6, a3
+	addi	a2, a2, 1
+.Lzerobit:
+	slli	a2, a2, 1
+	srli	a3, a3, 1
+#if !XCHAL_HAVE_LOOPS
+	addi	a4, a4, -1
+	bnez	a4, .Lloop
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lloopend:
+
+	bltu	a6, a3, .Lreturn
+	addi	a2, a2, 1	/* increment quotient if dividend >= divisor */
+.Lreturn:
+	abi_ret_default
+
+.Lle_one:
+	beqz	a3, .Lerror	/* if divisor == 1, return the dividend */
+	abi_ret_default
+
+.Lspecial:
+	/* return dividend >= divisor */
+	bltu	a6, a3, .Lreturn0
+	movi	a2, 1
+	abi_ret_default
+
+.Lerror:
+	/* Divide by zero: Use an illegal instruction to force an exception.
+	   The subsequent "DIV0" string can be recognized by the exception
+	   handler to identify the real cause of the exception.  */
+	ill
+	.ascii	"DIV0"
+
+.Lreturn0:
+	movi	a2, 0
+#endif /* XCHAL_HAVE_DIV32 */
+	abi_ret_default
+
+ENDPROC(__udivsi3)

arch/xtensa/lib/umodsi3.S

+/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+ENTRY(__umodsi3)
+
+	abi_entry_default
+#if XCHAL_HAVE_DIV32
+	remu	a2, a2, a3
+#else
+	bltui	a3, 2, .Lle_one	/* check if the divisor is <= 1 */
+
+	do_nsau	a5, a2, a6, a7	/* dividend_shift = nsau (dividend) */
+	do_nsau	a4, a3, a6, a7	/* divisor_shift = nsau (divisor) */
+	bgeu	a5, a4, .Lspecial
+
+	sub	a4, a4, a5	/* count = divisor_shift - dividend_shift */
+	ssl	a4
+	sll	a3, a3		/* divisor <<= count */
+
+	/* test-subtract-and-shift loop */
+#if XCHAL_HAVE_LOOPS
+	loopnez	a4, .Lloopend
+#endif /* XCHAL_HAVE_LOOPS */
+.Lloop:
+	bltu	a2, a3, .Lzerobit
+	sub	a2, a2, a3
+.Lzerobit:
+	srli	a3, a3, 1
+#if !XCHAL_HAVE_LOOPS
+	addi	a4, a4, -1
+	bnez	a4, .Lloop
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lloopend:
+
+.Lspecial:
+	bltu	a2, a3, .Lreturn
+	sub	a2, a2, a3	/* subtract once more if dividend >= divisor */
+.Lreturn:
+	abi_ret_default
+
+.Lle_one:
+	bnez	a3, .Lreturn0
+
+	/* Divide by zero: Use an illegal instruction to force an exception.
+	   The subsequent "DIV0" string can be recognized by the exception
+	   handler to identify the real cause of the exception.  */
+	ill
+	.ascii	"DIV0"
+
+.Lreturn0:
+	movi	a2, 0
+#endif /* XCHAL_HAVE_DIV32 */
+	abi_ret_default
+
+ENDPROC(__umodsi3)