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authorMichal Simek <michal.simek@xilinx.com>2022-02-25 14:55:35 +0100
committerMichal Simek <michal.simek@xilinx.com>2022-04-21 10:54:20 +0200
commit95fee37be45f443a8a322ee7f6f78167b73f2abc (patch)
treee1ceab05f04971000d00154c57a53dd61667f62d /arch/microblaze
parent8f0f265e6cf5b6d99a5a5d01b36985bc1131183e (diff)
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 <michal.simek@xilinx.com> Signed-off-by: Mahesh Bodapati <mbodapat@xilinx.com> Link: https://lore.kernel.org/r/10a432e269a6d3349cf458e4f5792522779cba0d.1645797329.git.michal.simek@xilinx.com
Diffstat (limited to 'arch/microblaze')
-rw-r--r--arch/microblaze/lib/memset.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/microblaze/lib/memset.c b/arch/microblaze/lib/memset.c
index 615a2f8f53cb..7c2352d56bb0 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;
}