sepavloff added inline comments.
================
Comment at: lib/CodeGen/CGExprConstant.cpp:1414-1415
+ Expr::EvalResult Result;
+ if (Init->EvaluateAsRValue(Result, CE.CGM.getContext()) &&
+ !Result.hasUnacceptableSideEffect(Expr::SE_NoSideEffects))
+ return (Result.Val.isInt() && Result.Val.getInt().isNullValue()) ||
----------------
rsmith wrote:
> Please call `D.evaluateValue()` here rather than inventing your own
> evaluation scheme. That way, we'll cache the evaluated initializer on the
> variable for other uses or reuse the value if we've already evaluated it, and
> you don't need to worry about the corner cases involved in getting the
> evaluation right. (As it happens, you're getting some minor details wrong
> because evaluating an initializer is not quite the same as evaluating an
> rvalue, but in practice it's not a big deal here.)
Call of `D.evaluateValue()` may result in substantial memory and time
consumption if the variable value is huge, like in:
```
int char data_1[2147483648u] = { 0 };
```
The idea of this patch is to recognize some cases of zero initialization prior
to the evaluation of variable initializer. In the example above, value would be
evaluated only for part of the initializer, namely `0`, which does not have an
associated variable, so call of `D.evaluateValue()` is not possible.
Repository:
rC Clang
https://reviews.llvm.org/D46241
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