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A comment on “Fiercely resist any further broadening of the scope of the C UB problem”. Parent comment

Re:“Fiercely resist any further broadening of the scope of t... by pcwalton on Thursday April 14, 2016 @01:50PM (#11498931)
> I doubt that anyone has ever filed a bug saying "I explicitly wrote a loop to zero memory, but the compiler failed to optimize it out."

That optimization is a natural consequence of SROA and DCE. If you claim you don't want those optimizations, I don't know what to tell you. Those optimizations are some of the most basic, critical optimizations any modern C/C++ compiler does and throwing them away can easily result in at least a 2x performance loss.

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Re:“Fiercely resist any further broadening of the scope of t... by cwzwarich on Thursday April 14, 2016 @03:37PM (#11499713)
The optimization actually has very little to do with SROA. In LLVM there is a special loop idiom recognition pass designed to detect memset / memcpy loops that works after ordinary SSA conversion.
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