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From: Maynard J. <may...@us...> - 2012-09-19 16:02:58
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On 09/08/2012 10:33 PM, Florian Krohm wrote: > On 09/08/2012 06:18 PM, Julian Seward wrote: > >> This is one of those things that has no effect for 99.99% of cases >> but may have a big impact for the cases it hits. I suspect it >> would be easy to write a test case that shows it -- a single >> basic block that contains a lot of both kinds of instructions, >> iterated over a lot, with suitable rounding mode setup beforehand. Hi, Florian, Finally got back to this. Sorry for the delay. I wrote a simple testcase as described, using fmul and dmul in a loop, iterated over 500,000 times. Valgrind executes the testcase in ~0.5 seconds. I did a trace with the VEX_TRACE_ASM flag and ensured that the mtfsf instruction was being done before the dmul and the fmul. So it seems to me this is not a big impact. I'm inclined to do nothing here, following the adage of "if it ain't broke, don't fix it." -Maynard >> >> The tricky bit is to ensure it is right. > > Huh? This looks like a fairly straight forward change to me.. > Anyhow, I was not planning to change the ppc code. I'll leave that to > Carl, Maynard, and you to decide. > Yes, a contrived testcase would be interesting but I'm the wrong person > to write it. > > Florian > |