Christophe Leroy 0b0057cc41 powerpc/bitops: Force inlining of fls() ...

Building a kernel with CONFIG_CC_OPTIMISE_FOR_SIZE leads to
the following functions being copied several times in vmlinux:

	31 times __ilog2_u32()
	34 times fls()

Disassembly follows:

	c00f476c <fls>:
	c00f476c:	7c 63 00 34 	cntlzw  r3,r3
	c00f4770:	20 63 00 20 	subfic  r3,r3,32
	c00f4774:	4e 80 00 20 	blr

	c00f4778 <__ilog2_u32>:
	c00f4778:	94 21 ff f0 	stwu    r1,-16(r1)
	c00f477c:	7c 08 02 a6 	mflr    r0
	c00f4780:	90 01 00 14 	stw     r0,20(r1)
	c00f4784:	4b ff ff e9 	bl      c00f476c <fls>
	c00f4788:	80 01 00 14 	lwz     r0,20(r1)
	c00f478c:	38 63 ff ff 	addi    r3,r3,-1
	c00f4790:	7c 08 03 a6 	mtlr    r0
	c00f4794:	38 21 00 10 	addi    r1,r1,16
	c00f4798:	4e 80 00 20 	blr

When forcing inlining of fls(), we get

	c0008b80 <__ilog2_u32>:
	c0008b80:	7c 63 00 34 	cntlzw  r3,r3
	c0008b84:	20 63 00 1f 	subfic  r3,r3,31
	c0008b88:	4e 80 00 20 	blr

vmlinux size gets reduced by 1 kbyte with that change.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/adc9c9d6378f6b5008246ca717993d7870188efb.1644569473.git.christophe.leroy@csgroup.eu

2022-03-08 22:33:03 +11:00

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