[LLVMdev] value tracking (original) (raw)
陳韋任 chenwj.cs97g+llvmdev at g2.nctu.edu.tw
Wed Feb 4 17:37:57 PST 2015
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Hi Xin Tong,
On Thu, Feb 5, 2015 at 7:46 AM, Xin Tong <trent.tong at gmail.com> wrote:
I would like to know what API i can use to tell that x cant be negative. I looked through the value tracking analysis API, nothing seems immediate.
int divBy4(int x) { if (x < 0) abort(); return x/4; } http://llvm.org/docs/doxygen/html/ValueTracking8h.html
How about llvm::ComputeSignBit? I think you can tell it's negative by the sign bit, right?
Regards, chenwj
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