Re: [PATCH 2/8] compat: make gcc bswap an inline function

Jonathan Nieder [off-list ref] writes:

Johannes Sixt wrote:

quoted

Am 3/16/2011 8:00, schrieb Jonathan Nieder:

quoted

quoted

+static inline uint32_t git_bswap32(uint32_t x)
+{
+	uint32_t result;
+	if (__builtin_constant_p(x))

Can this predicate ever be true? Isn't it false even if the function is
inlined?

It's true if x is a constant.
... demonstration ...

And this trivial function:

    int f(void) {
            return git_bswap32(0x01000000);
    }

compiles down to:

    .globl f
            .type   f, @function
    f:
    .LFB2:
            .cfi_startproc
            movl    $1, %eax
            ret
            .cfi_endproc

on my amd64, with -Os, -O1, or -O2 (gcc 4.4.5). Of course -O0 gives a true
call to git_bswap32() and leaves the definitions of two helper functions
in the object, but that is to be expected.