From 95fee37be45f443a8a322ee7f6f78167b73f2abc Mon Sep 17 00:00:00 2001 From: Michal Simek Date: Fri, 25 Feb 2022 14:55:35 +0100 Subject: [PATCH] microblaze: Do loop unrolling for optimized memset implementation Align implementation with memcpy and memmove where also remaining bytes are copied via final switch case instead of using simple implementations which loop. But this alignment has much stronger reason and definitely aligning implementation is not the key point here. It is just good to have in mind that the same technique is used already there. In GCC 10, now -ftree-loop-distribute-patterns optimization is on at O2. This optimization causes GCC to convert the while loop in memset.c into a call to memset. So this optimization is transforming a loop in a memset/memcpy into a call to the function itself. This makes the memset implementation as recursive. "-freestanding" option will disable the built-in library function but it has been added in generic library implementation. In default microblaze kernel defconfig we have CONFIG_OPT_LIB_FUNCTION enabled so it will always pick optimized version of memset which is target specific so we are replacing the while() loop with switch case to avoid recursive memset call. Issue with freestanding was already discussed in connection to commit 33d0f96ffd73 ("lib/string.c: Use freestanding environment") and also this is topic in glibc and gcc. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888 http://patchwork.ozlabs.org/project/glibc/patch/20191121021040.14554-1-sandra@codesourcery.com/ Signed-off-by: Michal Simek Signed-off-by: Mahesh Bodapati Link: https://lore.kernel.org/r/10a432e269a6d3349cf458e4f5792522779cba0d.1645797329.git.michal.simek@xilinx.com --- arch/microblaze/lib/memset.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/microblaze/lib/memset.c b/arch/microblaze/lib/memset.c index 615a2f8..7c2352d 100644 --- a/arch/microblaze/lib/memset.c +++ b/arch/microblaze/lib/memset.c @@ -74,8 +74,19 @@ void *memset(void *v_src, int c, __kernel_size_t n) } /* Simple, byte oriented memset or the rest of count. */ - while (n--) + switch (n) { + case 3: *src++ = c; + fallthrough; + case 2: + *src++ = c; + fallthrough; + case 1: + *src++ = c; + break; + default: + break; + } return v_src; } -- 2.7.4