search for: d70749

...null null) is f(poison), this is incorrect. If ptr was null, the added llvm.assume(ptr != null) raises UB whereas the source may not raise UB at all. (e.g. assume that f() was an empty function) If f(nonnull null) is UB, this is correct. 4. Dead argument elimination (from https://reviews.llvm.org/D70749 ) f(nonnull ptr); // f’s argument is dead => f(nonnull undef); This is incorrect if f(nonnull null) is UB. To make this correct, nonnull should be dropped. This becomes harder to fix if nonnull was attached at the signature of a function (not at the callee site). It is correct if f(nonnull nul...

...ms we had in the past, e.g., memcpy(NULL, NULL, 0), since the pointers in this example were "not used" (in some naive implementation of memcpy at least). Maybe I have overlooked a problem with this solution so let me know what you think. Cheers, Johannes [0] https://reviews.llvm.org/D70749 [1] 1. below: https://godbolt.org/z/J4wFVw [2] 2. below: https://godbolt.org/z/TAkSC6 [3] 3. below: https://godbolt.org/z/UqYi6S (doesn't work yet, will though) [4] 4. below: https://godbolt.org/z/Qkkc_E https://godbolt.org/z/uXAfp_ ... On 02/18, Juneyoung Lee via l...

...the pointers in > this example were "not used" (in some naive implementation of memcpy > at least). > > Maybe I have overlooked a problem with this solution so let me know > what you think. > > Cheers, > Johannes > > > [0] https://reviews.llvm.org/D70749 > [1] 1. below: https://godbolt.org/z/J4wFVw [2] 2. below: > https://godbolt.org/z/TAkSC6 [3] 3. below: > https://godbolt.org/z/UqYi6S (doesn't work yet, will though) [4] 4. > below: https://godbolt.org/z/Qkkc_E > https://godbolt.org/z/uXAfp_ > ....

...t;not used" (in some naive implementation of memcpy > > at least). > > > > Maybe I have overlooked a problem with this solution so let me know > > what you think. > > > > Cheers, > > Johannes > > > > > > [0] https://reviews.llvm.org/D70749 > > [1] 1. below: https://godbolt.org/z/J4wFVw [2] 2. below: > > https://godbolt.org/z/TAkSC6 [3] 3. below: > > https://godbolt.org/z/UqYi6S (doesn't work yet, will though) [4] 4. > > below: https://godbolt.org/z/Qkkc_E > > https://godbolt.org/z/uXAfp...

On 11/27/19 2:10 AM, Eli Friedman via llvm-dev wrote: The shuffle mask of a shufflevector is special: it's required to be a constant in a specific form. From LangRef: "The shuffle mask operand is required to be a constant vector with either constant integer or undef values." So really, we can resolve this any way we want; "undef" in this context doesn't have to mean