Re: [PATCH 7/9] RISC-V: don't use x8/s0/fp in assembly

[Antony Pavlov <antonynpavlov@gmail.com>]

On Sat, 8 Jan 2022 19:25:03 +0100
Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:

Hi Ahmad!

> Hello Antony,
> 
> On 08.01.22 18:15, Ahmad Fatoum wrote:
> > Free up the register to allow building a configuration with x8/s0 used
> > as the frame pointer.
> > 
> > Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> > ---
> >  arch/riscv/include/asm/debug_ll_litex.h   | 12 +++---
> >  arch/riscv/include/asm/debug_ll_ns16550.h |  8 ++--
> >  arch/riscv/include/asm/riscv_nmon.h       | 50 +++++++++++------------
> 
> I just bumped the s register: s2 -> s3, s1 -> s2, s0 -> s1 to
> clear s0. Is that ok?

I suppose that there is no problem if nmon still works under qemu.


> >  3 files changed, 35 insertions(+), 35 deletions(-)
> > 
> > diff --git a/arch/riscv/include/asm/debug_ll_litex.h b/arch/riscv/include/asm/debug_ll_litex.h
> > index 2fcdd9b0ec3e..295477fc1010 100644
> > --- a/arch/riscv/include/asm/debug_ll_litex.h
> > +++ b/arch/riscv/include/asm/debug_ll_litex.h
> > @@ -90,11 +90,11 @@ static inline void PUTC_LL(char ch)
> >  	li	t0, DEBUG_LL_UART_ADDR
> >  
> >  	/* get line status and check for data present */
> > -	lbu	s0, UART_RXEMPTY(t0)
> > -	bnez    s0, 243f
> > -	li	s0, 1
> > +	lbu	s1, UART_RXEMPTY(t0)
> > +	bnez    s1, 243f
> > +	li	s1, 1
> >  	j	244f
> > -243:	li	s0, 0
> > +243:	li	s1, 0
> >  244:	nop
> >  #endif /* CONFIG_DEBUG_LL */
> >  .endm
> > @@ -109,10 +109,10 @@ static inline void PUTC_LL(char ch)
> >  	debug_ll_tstc
> >  
> >  	/* try again */
> > -	beqz	s0, 204b
> > +	beqz	s1, 204b
> >  
> >  	/* read a character */
> > -	lb	s0, UART_RXTX(t0)
> > +	lb	s1, UART_RXTX(t0)
> >  	li      t1, UART_EV_RX
> >  	sb	t1, UART_EV_PENDING(t0)
> >  
> > diff --git a/arch/riscv/include/asm/debug_ll_ns16550.h b/arch/riscv/include/asm/debug_ll_ns16550.h
> > index e208ef4fb1e1..47f0be328ce8 100644
> > --- a/arch/riscv/include/asm/debug_ll_ns16550.h
> > +++ b/arch/riscv/include/asm/debug_ll_ns16550.h
> > @@ -143,8 +143,8 @@ static inline void debug_ll_ns16550_init(void)
> >  	li      t0, DEBUG_LL_UART_ADDR
> >  
> >  	/* get line status and check for data present */
> > -	UART_REG_L	s0, UART_LSR(DEBUG_LL_UART_SHIFT)(t0)
> > -	andi	s0, s0, UART_LSR_DR
> > +	UART_REG_L	s1, UART_LSR(DEBUG_LL_UART_SHIFT)(t0)
> > +	andi	s1, s1, UART_LSR_DR
> >  
> >  #endif /* CONFIG_DEBUG_LL */
> >  .endm
> > @@ -159,10 +159,10 @@ static inline void debug_ll_ns16550_init(void)
> >  	debug_ll_tstc
> >  
> >  	/* try again */
> > -	beqz	s0, 204b
> > +	beqz	s1, 204b
> >  
> >  	/* read a character */
> > -	UART_REG_L	s0, UART_RBR(DEBUG_LL_UART_SHIFT)(t0)
> > +	UART_REG_L	s1, UART_RBR(DEBUG_LL_UART_SHIFT)(t0)
> >  
> >  #endif /* CONFIG_DEBUG_LL */
> >  .endm
> > diff --git a/arch/riscv/include/asm/riscv_nmon.h b/arch/riscv/include/asm/riscv_nmon.h
> > index 8a44e216d72d..3e349025febc 100644
> > --- a/arch/riscv/include/asm/riscv_nmon.h
> > +++ b/arch/riscv/include/asm/riscv_nmon.h
> > @@ -84,7 +84,7 @@ nmon_main:
> >  	debug_ll_getc
> >  
> >  	li	a0, 'q'
> > -	bne	s0, a0, 3f
> > +	bne	s1, a0, 3f
> >  
> >  	jal	a2, _nmon_outc_a0
> >  
> > @@ -92,13 +92,13 @@ nmon_main:
> >  
> >  3:
> >  	li	a0, 'd'
> > -	beq	s0, a0, nmon_cmd_d
> > +	beq	s1, a0, nmon_cmd_d
> >  
> >  	li	a0, 'w'
> > -	beq	s0, a0, nmon_cmd_w
> > +	beq	s1, a0, nmon_cmd_w
> >  
> >  	li	a0, 'g'
> > -	beq	s0, a0, nmon_cmd_g
> > +	beq	s1, a0, nmon_cmd_g
> >  
> >  	j	nmon_main_help
> >  
> > @@ -112,7 +112,7 @@ nmon_cmd_d:
> >  
> >  	nmon_outs	msg_nl
> >  
> > -	lw	a0, (s0)
> > +	lw	a0, (s1)
> >  	debug_ll_outhexw
> >  
> >  	j	nmon_main
> > @@ -124,13 +124,13 @@ nmon_cmd_w:
> >  	jal	a2, _nmon_outc_a0
> >  
> >  	jal	a2, _nmon_gethexw
> > -	move	s2, s0
> > +	move	s3, s1
> >  
> >  	li	a0, ' '
> >  	jal	a2, _nmon_outc_a0
> >  	jal	a2, _nmon_gethexw
> >  
> > -	sw	s0, 0(s2)
> > +	sw	s1, 0(s3)
> >  	j	nmon_main
> >  
> >  nmon_cmd_g:
> > @@ -140,11 +140,11 @@ nmon_cmd_g:
> >  	jal	a2, _nmon_outc_a0
> >  
> >  	jal	a2, _nmon_gethexw
> > -	move	s2, s0
> > +	move	s3, s1
> >  
> >  	nmon_outs	msg_nl
> >  
> > -	jalr	s2
> > +	jalr	s3
> >  	j	nmon_main
> >  
> >  _nmon_outc_a0:
> > @@ -169,37 +169,37 @@ _nmon_gethexw:
> >  _get_hex_digit:
> >  	debug_ll_getc
> >  
> > -	li	s1, CODE_ESC
> > -	beq	s0, s1, nmon_main
> > +	li	s2, CODE_ESC
> > +	beq	s1, s2, nmon_main
> >  
> > -	li	s1, '0'
> > -	bge	s0, s1, 0f
> > +	li	s2, '0'
> > +	bge	s1, s2, 0f
> >  	j	_get_hex_digit
> >  
> >  0:
> > -	li	s1, '9'
> > -	ble	s0, s1, 9f
> > +	li	s2, '9'
> > +	ble	s1, s2, 9f
> >  
> > -	li	s1, 'f'
> > -	ble	s0, s1, 1f
> > +	li	s2, 'f'
> > +	ble	s1, s2, 1f
> >  	j	_get_hex_digit
> >  
> >  1:
> > -	li	s1, 'a'
> > -	bge	s0, s1, 8f
> > +	li	s2, 'a'
> > +	bge	s1, s2, 8f
> >  
> >  	j	_get_hex_digit
> >  
> > -8: /* s0 \in {'a', 'b' ... 'f'} */
> > -	sub	a3, s0, s1
> > +8: /* s1 \in {'a', 'b' ... 'f'} */
> > +	sub	a3, s1, s2
> >  	addi	a3, a3, 0xa
> >  	j	0f
> >  
> > -9: /* s0 \in {'0', '1' ... '9'} */
> > +9: /* s1 \in {'0', '1' ... '9'} */
> >  	li	a3, '0'
> > -	sub	a3, s0, a3
> > +	sub	a3, s1, a3
> >  
> > -0:	move	a0, s0
> > +0:	move	a0, s1
> >  	debug_ll_outc_a0
> >  
> >  	sll	t2, t2, 4
> > @@ -212,7 +212,7 @@ _get_hex_digit:
> >  	j	_get_hex_digit
> >  
> >  0:
> > -	move	s0, t2
> > +	move	s1, t2
> >  
> >  _nmon_jr_ra_exit:
> >  	jr	a2
> > 
> 
> 
> -- 
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-- 
Best regards,
  Antony Pavlov

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