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[llvm-dev] Is there a simple way to check APInt multiplication overflow?

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Hello,


I have two APInt variables, which are got by ConstantSDNode::getAPIntValue().


Is there a simple way to know if their multiplication overflows?


For example, if both APInt vars contain a int32_t, 
APInt a, b;
Then I think 


if (a.getMinSignedBits() + b.getMinSignedBits() > 32)
   a*b must exceeds int32_t <=> overflow happens;


Is my way OK?


Ben Shi
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