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PCI: Optimize pci_resource_len() to reduce kernel size

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pci_resource_end() can be 0 only when pci_resource_start() is 0.
Otherwise, it is definitely an error. In this case, pci_resource_len()
should be regarded as 0. Therefore, determining whether
pci_resource_start() and pci_resource_end() are both 0 can be reduced to
determining only whether pci_resource_end() is 0.

Although only one condition judgment is reduced, the macro function
pci_resource_len() is widely referenced in the kernel. I used defconfig to
compile the latest kernel on X86, and its binary code size was reduced by
about 3KB.

  Before:
   [ 2] .rela.text        RELA             0000000000000000  093bfcb0
        0000000001a67168  0000000000000018   I      68     1     8

  After:
   [ 2] .rela.text        RELA             0000000000000000  093bfcb0
        0000000001a66598  0000000000000018   I      68     1     8

Link: https://lore.kernel.org/r/20210713072236.3043-1-thunder.leizhen@huawei.com
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Zhen Lei 2021-07-13 15:22:36 +08:00 committed by Bjorn Helgaas
parent a67462fc9d
commit ca32b5310a
1 changed files with 1 additions and 3 deletions
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4
include/linux/pci.h
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@ -1881,9 +1881,7 @@ int pci_iobar_pfn(struct pci_dev *pdev, int bar, struct vm_area_struct *vma);
#define pci_resource_end(dev, bar) ((dev)->resource[(bar)].end)
#define pci_resource_flags(dev, bar) ((dev)->resource[(bar)].flags)
#define pci_resource_len(dev,bar) \
((pci_resource_start((dev), (bar)) == 0 && \
pci_resource_end((dev), (bar)) == \
pci_resource_start((dev), (bar))) ? 0 : \
((pci_resource_end((dev), (bar)) == 0) ? 0 : \
\
(pci_resource_end((dev), (bar)) - \
pci_resource_start((dev), (bar)) + 1))