Unbreak high resolution profiling a little: use dummy asms to prevent
timing loops being optimized away. Once apon a time, gcc promised not to optimize away timing loops, but gcc started optimizing away the call to a null function in the timing loop here some time between gcc-3.3.3 and gcc-3.4.6, and it started optimizing away the timing loop itself some time between gcc-3.4.6 and gcc-4.2.
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=170659
@ -268,18 +268,23 @@ mexitcount(selfpc)
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}
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}
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#ifndef __GNUCLIKE_ASM
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#error "This file uses null asms to prevent timing loops being optimized away."
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#endif
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void
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empty_loop()
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{
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int i;
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for (i = 0; i < CALIB_SCALE; i++)
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;
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__asm __volatile("");
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}
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void
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nullfunc()
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{
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__asm __volatile("");
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}
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void
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