From ff5fdafc9e9702846480e0cea55ba861f72140a2 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Fri, 19 Jan 2018 18:17:46 +0100 Subject: ARM: 8745/1: get rid of __memzero() The __memzero assembly code is almost identical to memset's except for two orr instructions. The runtime performance of __memset(p, n) and memset(p, 0, n) is accordingly almost identical. However, the memset() macro used to guard against a zero length and to call __memzero at compile time when the fill value is a constant zero interferes with compiler optimizations. Arnd found tha the test against a zero length brings up some new warnings with gcc v8: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82103 And successively rremoving the test against a zero length and the call to __memzero optimization produces the following kernel sizes for defconfig with gcc 6: text data bss dec hex filename 12248142 6278960 413588 18940690 1210312 vmlinux.orig 12244474 6278960 413588 18937022 120f4be vmlinux.no_zero_test 12239160 6278960 413588 18931708 120dffc vmlinux.no_memzero So it is probably not worth keeping __memzero around given that the compiler can do a better job at inlining trivial memset(p,0,n) on its own. And the memset code already handles a zero length just fine. Suggested-by: Arnd Bergmann Signed-off-by: Nicolas Pitre Acked-by: Ard Biesheuvel Acked-by: Arnd Bergmann Signed-off-by: Russell King --- drivers/dma/imx-dma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/dma') diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c index 331f863c605e..715b39ae5a46 100644 --- a/drivers/dma/imx-dma.c +++ b/drivers/dma/imx-dma.c @@ -765,7 +765,7 @@ static int imxdma_alloc_chan_resources(struct dma_chan *chan) desc = kzalloc(sizeof(*desc), GFP_KERNEL); if (!desc) break; - __memzero(&desc->desc, sizeof(struct dma_async_tx_descriptor)); + memset(&desc->desc, 0, sizeof(struct dma_async_tx_descriptor)); dma_async_tx_descriptor_init(&desc->desc, chan); desc->desc.tx_submit = imxdma_tx_submit; /* txd.flags will be overwritten in prep funcs */ -- cgit v1.2.1