diff_filespec: reorder is_binary field
The middle of the diff_filespec struct contains a mixture of ints, shorts, and bit-fields, followed by a pointer. On an x86-64 system with an LP64 or LLP64 data model (i.e., most of them), the integers and flags end up being padded out by 41 bits to put the pointer at an 8-byte boundary. After the pointer, we have the "int is_binary" field, which is only 32 bits. We end up wasting another 32 bits to pad the struct size up to a multiple of 64 bits. We can move the is_binary field before the pointer, which lets the compiler store it where we used to have padding. This shrinks the top padding to only 9 bits (from the bit-fields), and eliminates the bottom padding entirely, dropping the struct size from 88 to 80 bytes. On a 32-bit system, there is no benefit, but nor should there be any harm (we only need 4-byte alignment there, so we were already using only 9 bits of padding). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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@ -45,9 +45,9 @@ struct diff_filespec {
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#define DIRTY_SUBMODULE_MODIFIED 2
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unsigned is_stdin : 1;
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unsigned has_more_entries : 1; /* only appear in combined diff */
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struct userdiff_driver *driver;
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/* data should be considered "binary"; -1 means "don't know yet" */
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int is_binary;
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struct userdiff_driver *driver;
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};
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extern struct diff_filespec *alloc_filespec(const char *);
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