Messages in this thread Patch in this message | | | Date | Wed, 5 Jan 2022 21:01:10 +0100 | From | Alexandre Belloni <> | Subject | Re: [PATCH] rtc: isl1208: avoid unnecessary rc variable tests |
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On 05/01/2022 14:34:39-0500, Hugo Villeneuve wrote: > From: Hugo Villeneuve <hvilleneuve@dimonoff.com> > > The rc variable doesn't need to be tested a second time when the <if> block > evaluates to false. >
rc is not tested a second time, here is the relevant listing:
- if (client->irq > 0) + if (client->irq > 0) { ffffffff81aef647: 41 8b b5 bc 01 00 00 mov 0x1bc(%r13),%esi ffffffff81aef64e: 85 f6 test %esi,%esi ffffffff81aef650: 0f 8f 35 01 00 00 jg ffffffff81aef78b <isl1208_probe+0x314> rc = isl1208_setup_irq(client, client->irq); if (rc) return rc; + } - if (evdet_irq > 0 && evdet_irq != client->irq) + if (evdet_irq > 0 && evdet_irq != client->irq) { ffffffff81aef656: 85 db test %ebx,%ebx ffffffff81aef658: 7e 0d jle ffffffff81aef667 <isl1208_probe+0x1f0> ffffffff81aef65a: 41 39 9d bc 01 00 00 cmp %ebx,0x1bc(%r13) @@ -1663,6 +1664,7 @@ ffffffff81aef661: 0f 85 0a 01 00 00 rc = isl1208_setup_irq(client, evdet_irq); if (rc) return rc; + }
As you can see, no change in assembly but it is worse to read. gcc on arm behaves the same way.
> Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com> > --- > drivers/rtc/rtc-isl1208.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/drivers/rtc/rtc-isl1208.c b/drivers/rtc/rtc-isl1208.c > index 182dfa605515..c7f04df5a0b6 100644 > --- a/drivers/rtc/rtc-isl1208.c > +++ b/drivers/rtc/rtc-isl1208.c > @@ -880,15 +880,17 @@ isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id) > if (rc) > return rc; > > - if (client->irq > 0) > + if (client->irq > 0) { > rc = isl1208_setup_irq(client, client->irq); > - if (rc) > - return rc; > + if (rc) > + return rc; > + } > > - if (evdet_irq > 0 && evdet_irq != client->irq) > + if (evdet_irq > 0 && evdet_irq != client->irq) { > rc = isl1208_setup_irq(client, evdet_irq); > - if (rc) > - return rc; > + if (rc) > + return rc; > + } > > rc = devm_rtc_nvmem_register(isl1208->rtc, &isl1208->nvmem_config); > if (rc) > -- > 2.30.2 >
-- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
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