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Date: Fri, 27 Jul 2018 23:23:49 +0300
From: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To: Joe Perches <joe@...ches.com>
Cc: grygorii.strashko@...com, davem@...emloft.net,
linux-omap@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: ethernet: ti: cpsw: replace unnecessarily
macroses on functions
On Fri, Jul 27, 2018 at 01:04:22PM -0700, Joe Perches wrote:
>On Fri, 2018-07-27 at 22:36 +0300, Ivan Khoronzhuk wrote:
>> On Fri, Jul 27, 2018 at 12:21:07PM -0700, Joe Perches wrote:
>> > On Fri, 2018-07-27 at 22:13 +0300, Ivan Khoronzhuk wrote:
>> > > Replace ugly macroses on functions.
>> >
>> > Careful, see below.
>> >
>> > > diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
>> >
>> > []
>> > > @@ -565,40 +565,40 @@ static const struct cpsw_stats cpsw_gstrings_ch_stats[] = {
>> > > (func)(slave++, ##arg); \
>> > > } while (0)
>> > >
>> > > -#define cpsw_dual_emac_src_port_detect(cpsw, status, ndev, skb) \
>> > > - do { \
>> > > - if (!cpsw->data.dual_emac) \
>> > > - break; \
>> > > - if (CPDMA_RX_SOURCE_PORT(status) == 1) { \
>> > > - ndev = cpsw->slaves[0].ndev; \
>> > > - skb->dev = ndev; \
>> > > - } else if (CPDMA_RX_SOURCE_PORT(status) == 2) { \
>> > > - ndev = cpsw->slaves[1].ndev; \
>> > > - skb->dev = ndev; \
>> > > - } \
>> > > - } while (0)
>> > > -#define cpsw_add_mcast(cpsw, priv, addr) \
>> > > - do { \
>> > > - if (cpsw->data.dual_emac) { \
>> > > - struct cpsw_slave *slave = cpsw->slaves + \
>> > > - priv->emac_port; \
>> > > - int slave_port = cpsw_get_slave_port( \
>> > > - slave->slave_num); \
>> > > - cpsw_ale_add_mcast(cpsw->ale, addr, \
>> > > - 1 << slave_port | ALE_PORT_HOST, \
>> > > - ALE_VLAN, slave->port_vlan, 0); \
>> > > - } else { \
>> > > - cpsw_ale_add_mcast(cpsw->ale, addr, \
>> > > - ALE_ALL_PORTS, \
>> > > - 0, 0, 0); \
>> > > - } \
>> > > - } while (0)
>> > > -
>> > > static inline int cpsw_get_slave_port(u32 slave_num)
>> > > {
>> > > return slave_num + 1;
>> > > }
>> > >
>> > > +static inline void cpsw_src_port_detect(struct cpsw_common *cpsw, int status,
>> > > + struct sk_buff *skb)
>> > > +{
>> > > + if (!cpsw->data.dual_emac)
>> > > + return;
>> > > +
>> > > + if (CPDMA_RX_SOURCE_PORT(status) == 1)
>> > > + skb->dev = cpsw->slaves[0].ndev;
>> > > + else if (CPDMA_RX_SOURCE_PORT(status) == 2)
>> > > + skb->dev = cpsw->slaves[1].ndev;
>> > > +}
>> >
>> > perhaps better as a switch/case
>>
>> not better, it's shorter.
>
>True for the source code but it compiles to more object code.
>
>$ cat foo.c
>struct cpsw_common {
> struct {
> int dual_emac;
> } data;
> struct {
> int ndev;
> } slaves[2];
>};
>
>struct sk_buff {
> int dev;
>};
>
>#define CPDMA_RX_SOURCE_PORT(__status__) ((__status__ >> 16) & 0x7)
>
>#if defined SWITCH
>
>void foo(struct cpsw_common *cpsw, int status, struct sk_buff *skb)
>{
> if (!cpsw->data.dual_emac)
> return;
>
> switch (CPDMA_RX_SOURCE_PORT(status)) {
> case 1:
> skb->dev = cpsw->slaves[0].ndev;
> break;
> case 2:
> skb->dev = cpsw->slaves[1].ndev;
> break;
> }
>}
>
>#else
>
>void foo(struct cpsw_common *cpsw, int status, struct sk_buff *skb)
>{
> if (!cpsw->data.dual_emac)
> return;
>
> if (CPDMA_RX_SOURCE_PORT(status) == 1)
> skb->dev = cpsw->slaves[0].ndev;
> else if (CPDMA_RX_SOURCE_PORT(status) == 2)
> skb->dev = cpsw->slaves[1].ndev;
>}
>
>#endif
>$ gcc -c -O2 -DSWITCH foo.c
>$ size foo.o
> text data bss dec hex filename
> 94 0 0 94 5e foo.o
>$ objdump -d foo.o
>
>foo.o: file format elf64-x86-64
>
>
>Disassembly of section .text:
>
>0000000000000000 <foo>:
> 0: 8b 07 mov (%rdi),%eax
> 2: 85 c0 test %eax,%eax
> 4: 74 15 je 1b <foo+0x1b>
> 6: c1 fe 10 sar $0x10,%esi
> 9: 83 e6 07 and $0x7,%esi
> c: 83 fe 01 cmp $0x1,%esi
> f: 74 17 je 28 <foo+0x28>
> 11: 83 fe 02 cmp $0x2,%esi
> 14: 75 0a jne 20 <foo+0x20>
> 16: 8b 47 08 mov 0x8(%rdi),%eax
> 19: 89 02 mov %eax,(%rdx)
> 1b: f3 c3 repz retq
> 1d: 0f 1f 00 nopl (%rax)
> 20: f3 c3 repz retq
> 22: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
> 28: 8b 47 04 mov 0x4(%rdi),%eax
> 2b: 89 02 mov %eax,(%rdx)
> 2d: c3 retq
>$ gcc -c -O2 foo.c
>$ size foo.o
> text data bss dec hex filename
> 102 0 0 102 66 foo.o
>$ objdump -d foo.o
>
>foo.o: file format elf64-x86-64
>
>
>Disassembly of section .text:
>
>0000000000000000 <foo>:
> 0: 8b 07 mov (%rdi),%eax
> 2: 85 c0 test %eax,%eax
> 4: 74 10 je 16 <foo+0x16>
> 6: c1 fe 10 sar $0x10,%esi
> 9: 83 e6 07 and $0x7,%esi
> c: 83 fe 01 cmp $0x1,%esi
> f: 74 0f je 20 <foo+0x20>
> 11: 83 fe 02 cmp $0x2,%esi
> 14: 74 1a je 30 <foo+0x30>
> 16: f3 c3 repz retq
> 18: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1)
> 1f: 00
> 20: 8b 47 04 mov 0x4(%rdi),%eax
> 23: 89 02 mov %eax,(%rdx)
> 25: c3 retq
> 26: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
> 2d: 00 00 00
> 30: 8b 47 08 mov 0x8(%rdi),%eax
> 33: 89 02 mov %eax,(%rdx)
> 35: c3 retq
>
>
This driver, mainly used for ARM
For ARM, situation a little bit different:
$ arm-linux-gnueabihf-gcc -c -O2 -DSWITCH foo.c
$ size foo.o
text data bss dec hex filename
32 0 0 32 20 foo.o
$ arm-linux-gnueabihf-objdump -d foo.o
foo.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <foo>:
0: 6803 ldr r3, [r0, #0]
2: b143 cbz r3, 16 <foo+0x16>
4: f3c1 4102 ubfx r1, r1, #16, #3
8: 2901 cmp r1, #1
a: d005 beq.n 18 <foo+0x18>
c: 2902 cmp r1, #2
e: d000 beq.n 12 <foo+0x12>
10: 4770 bx lr
12: 6883 ldr r3, [r0, #8]
14: 6013 str r3, [r2, #0]
16: 4770 bx lr
18: 6843 ldr r3, [r0, #4]
1a: 6013 str r3, [r2, #0]
1c: 4770 bx lr
1e: bf00 nop
$ arm-linux-gnueabihf-gcc -c -O2 foo.c
$ size foo.o
text data bss dec hex filename
28 0 0 28 1c foo.o
$ arm-linux-gnueabihf-objdump -d foo.o
foo.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <foo>:
0: 6803 ldr r3, [r0, #0]
2: b13b cbz r3, 14 <foo+0x14>
4: f3c1 4102 ubfx r1, r1, #16, #3
8: 2901 cmp r1, #1
a: d004 beq.n 16 <foo+0x16>
c: 2902 cmp r1, #2
e: bf04 itt eq
10: 6883 ldreq r3, [r0, #8]
12: 6013 streq r3, [r2, #0]
14: 4770 bx lr
16: 6843 ldr r3, [r0, #4]
18: 6013 str r3, [r2, #0]
1a: 4770 bx lr
So, it's shorter.
--
Regards,
Ivan Khoronzhuk
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