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MIPS, Tracing: Speed up function graph tracer

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This simply moves the "ip-=4" statement down to the end of the do { ...
} while (...); loop, which reduces one unneeded subtration and the
subsequent memory loading and comparison.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2006/
Signed-off-by: Ralf Baechle <ralf@duck.linux-mips.net>
This commit is contained in:
Wu Zhangjin 2011-01-20 03:28:27 +08:00 committed by Ralf Baechle
parent 52bd080d5c
commit 9a620a559b
1 changed files with 7 additions and 7 deletions
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14
arch/mips/kernel/ftrace.c
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@ -200,19 +200,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
int faulted;
/*
* For module, move the ip from calling site of mcount to the
* instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
* kernel, move to the instruction "move ra, at"(offset is 12)
* For module, move the ip from calling site of mcount after the
* instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
* kernel, move after the instruction "move ra, at"(offset is 16)
*/
ip = self_addr - (in_module(self_addr) ? 20 : 12);
ip = self_addr - (in_module(self_addr) ? 24 : 16);
/*
* search the text until finding the non-store instruction or "s{d,w}
* ra, offset(sp)" instruction
*/
do {
ip -= 4;
/* get the code at "ip": code = *(unsigned int *)ip; */
safe_load_code(code, ip, faulted);
@ -226,7 +224,9 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
if ((code & S_R_SP) != S_R_SP)
return parent_addr;
} while (((code & S_RA_SP) != S_RA_SP));
/* Move to the next instruction */
ip -= 4;
} while ((code & S_RA_SP) != S_RA_SP);
sp = fp + (code & OFFSET_MASK);