MIPS, Tracing: Speed up function graph tracer
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>
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@ -200,19 +200,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
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int faulted;
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int faulted;
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/*
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/*
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* For module, move the ip from calling site of mcount to the
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* For module, move the ip from calling site of mcount after the
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* instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
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* instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
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* kernel, move to the instruction "move ra, at"(offset is 12)
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* kernel, move after the instruction "move ra, at"(offset is 16)
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*/
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*/
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ip = self_addr - (in_module(self_addr) ? 20 : 12);
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ip = self_addr - (in_module(self_addr) ? 24 : 16);
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/*
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/*
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* search the text until finding the non-store instruction or "s{d,w}
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* search the text until finding the non-store instruction or "s{d,w}
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* ra, offset(sp)" instruction
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* ra, offset(sp)" instruction
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*/
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*/
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do {
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do {
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ip -= 4;
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/* get the code at "ip": code = *(unsigned int *)ip; */
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/* get the code at "ip": code = *(unsigned int *)ip; */
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safe_load_code(code, ip, faulted);
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safe_load_code(code, ip, faulted);
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@ -226,7 +224,9 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
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if ((code & S_R_SP) != S_R_SP)
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if ((code & S_R_SP) != S_R_SP)
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return parent_addr;
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return parent_addr;
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} while (((code & S_RA_SP) != S_RA_SP));
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/* Move to the next instruction */
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ip -= 4;
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} while ((code & S_RA_SP) != S_RA_SP);
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sp = fp + (code & OFFSET_MASK);
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sp = fp + (code & OFFSET_MASK);
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