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[v2,2/4] RISC-V: reduce mcount save space on RV32

Message ID 20221115200832.706370-3-jamie@jamieiles.com (mailing list archive)
State Accepted
Commit 3bd7743f8d6d7171db9897a746038eefd52a1fbd
Delegated to: Palmer Dabbelt
Headers show
Series RISC-V: Dynamic ftrace support for RV32I | expand

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Commit Message

Jamie Iles Nov. 15, 2022, 8:08 p.m. UTC
For RV32 we can reduce the size of the ABI save+restore state by using
SZREG so that register stores are packed rather than on an 8 byte
boundary.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
---
 arch/riscv/kernel/mcount.S | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

Comments

Andrew Jones Nov. 16, 2022, 8:31 a.m. UTC | #1
On Tue, Nov 15, 2022 at 08:08:30PM +0000, Jamie Iles wrote:
> For RV32 we can reduce the size of the ABI save+restore state by using
> SZREG so that register stores are packed rather than on an 8 byte
> boundary.
> 
> Signed-off-by: Jamie Iles <jamie@jamieiles.com>
> ---
>  arch/riscv/kernel/mcount.S | 32 ++++++++++++++++----------------
>  1 file changed, 16 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
> index 9cf0904afd6d..613bd07c6268 100644
> --- a/arch/riscv/kernel/mcount.S
> +++ b/arch/riscv/kernel/mcount.S
> @@ -15,8 +15,8 @@
>  
>  	.macro SAVE_ABI_STATE
>  	addi	sp, sp, -16
> -	REG_S	s0, 0(sp)
> -	REG_S	ra, 8(sp)
> +	REG_S	s0, 0*SZREG(sp)
> +	REG_S	ra, 1*SZREG(sp)
>  	addi	s0, sp, 16
>  	.endm
>  
> @@ -25,24 +25,24 @@
>  	 * register if a0 was not saved.
>  	 */
>  	.macro SAVE_RET_ABI_STATE
> -	addi	sp, sp, -32
> -	REG_S	s0, 16(sp)
> -	REG_S	ra, 24(sp)
> -	REG_S	a0, 8(sp)
> -	addi	s0, sp, 32
> +	addi	sp, sp, -4*SZREG
> +	REG_S	s0, 2*SZREG(sp)
> +	REG_S	ra, 3*SZREG(sp)
> +	REG_S	a0, 1*SZREG(sp)

I probably would have taken the opportunity to put these lines
in ascending order by offset, since it looks odd like this.

Anyway,

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>


> +	addi	s0, sp, 4*SZREG
>  	.endm
>  
>  	.macro RESTORE_ABI_STATE
> -	REG_L	ra, 8(sp)
> -	REG_L	s0, 0(sp)
> +	REG_L	ra, 1*SZREG(sp)
> +	REG_L	s0, 0*SZREG(sp)
>  	addi	sp, sp, 16
>  	.endm
>  
>  	.macro RESTORE_RET_ABI_STATE
> -	REG_L	ra, 24(sp)
> -	REG_L	s0, 16(sp)
> -	REG_L	a0, 8(sp)
> -	addi	sp, sp, 32
> +	REG_L	ra, 3*SZREG(sp)
> +	REG_L	s0, 2*SZREG(sp)
> +	REG_L	a0, 1*SZREG(sp)
> +	addi	sp, sp, 4*SZREG
>  	.endm
>  
>  ENTRY(ftrace_stub)
> @@ -101,10 +101,10 @@ ENTRY(MCOUNT_NAME)
>   * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
>   */
>  do_ftrace_graph_caller:
> -	addi	a0, s0, -8
> +	addi	a0, s0, -SZREG
>  	mv	a1, ra
>  #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
> -	REG_L	a2, -16(s0)
> +	REG_L	a2, -2*SZREG(s0)
>  #endif
>  	SAVE_ABI_STATE
>  	call	prepare_ftrace_return
> @@ -117,7 +117,7 @@ do_ftrace_graph_caller:
>   * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
>   */
>  do_trace:
> -	REG_L	a1, -8(s0)
> +	REG_L	a1, -SZREG(s0)
>  	mv	a0, ra
>  
>  	SAVE_ABI_STATE
> -- 
> 2.37.2
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
diff mbox series

Patch

diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index 9cf0904afd6d..613bd07c6268 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -15,8 +15,8 @@ 
 
 	.macro SAVE_ABI_STATE
 	addi	sp, sp, -16
-	REG_S	s0, 0(sp)
-	REG_S	ra, 8(sp)
+	REG_S	s0, 0*SZREG(sp)
+	REG_S	ra, 1*SZREG(sp)
 	addi	s0, sp, 16
 	.endm
 
@@ -25,24 +25,24 @@ 
 	 * register if a0 was not saved.
 	 */
 	.macro SAVE_RET_ABI_STATE
-	addi	sp, sp, -32
-	REG_S	s0, 16(sp)
-	REG_S	ra, 24(sp)
-	REG_S	a0, 8(sp)
-	addi	s0, sp, 32
+	addi	sp, sp, -4*SZREG
+	REG_S	s0, 2*SZREG(sp)
+	REG_S	ra, 3*SZREG(sp)
+	REG_S	a0, 1*SZREG(sp)
+	addi	s0, sp, 4*SZREG
 	.endm
 
 	.macro RESTORE_ABI_STATE
-	REG_L	ra, 8(sp)
-	REG_L	s0, 0(sp)
+	REG_L	ra, 1*SZREG(sp)
+	REG_L	s0, 0*SZREG(sp)
 	addi	sp, sp, 16
 	.endm
 
 	.macro RESTORE_RET_ABI_STATE
-	REG_L	ra, 24(sp)
-	REG_L	s0, 16(sp)
-	REG_L	a0, 8(sp)
-	addi	sp, sp, 32
+	REG_L	ra, 3*SZREG(sp)
+	REG_L	s0, 2*SZREG(sp)
+	REG_L	a0, 1*SZREG(sp)
+	addi	sp, sp, 4*SZREG
 	.endm
 
 ENTRY(ftrace_stub)
@@ -101,10 +101,10 @@  ENTRY(MCOUNT_NAME)
  * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
  */
 do_ftrace_graph_caller:
-	addi	a0, s0, -8
+	addi	a0, s0, -SZREG
 	mv	a1, ra
 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
-	REG_L	a2, -16(s0)
+	REG_L	a2, -2*SZREG(s0)
 #endif
 	SAVE_ABI_STATE
 	call	prepare_ftrace_return
@@ -117,7 +117,7 @@  do_ftrace_graph_caller:
  * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
  */
 do_trace:
-	REG_L	a1, -8(s0)
+	REG_L	a1, -SZREG(s0)
 	mv	a0, ra
 
 	SAVE_ABI_STATE