[PATCH] D14479: Fix bug 25440: GVN assertion after coercing loads

[Daniel Berlin via llvm-commits]

This patch doesn't make sense.


Either  you need to have it assign the GV and fix the leader tables so that
the lookup at this point succeeds (which is ideal), or VN.lookup(op) ==
null, it should set success=false and break.


The former is *greatly* preferable to the latter.

What you've done here makes no sense, because findLeader(anything, <new
value number>) will always return nothing, since addLeaderToTable has not
been called on the new value number.
All you are doing in that case is wasting time calling findLeader.



On Fri, Nov 6, 2015 at 11:22 PM, Weiming Zhao via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> weimingz created this revision.
> weimingz added a subscriber: llvm-commits.
>
> when coercing loads, it inserts some instructions, which have no GV
> assigned.
>
> https://llvm.org/bugs/show_bug.cgi?id=25440
>
>
> http://reviews.llvm.org/D14479
>
> Files:
>   lib/Transforms/Scalar/GVN.cpp
>
> Index: lib/Transforms/Scalar/GVN.cpp
> ===================================================================
> --- lib/Transforms/Scalar/GVN.cpp
> +++ lib/Transforms/Scalar/GVN.cpp
> @@ -2529,7 +2529,7 @@
>      if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
>        continue;
>
> -    if (Value *V = findLeader(Pred, VN.lookup(Op))) {
> +    if (Value *V = findLeader(Pred, VN.lookup_or_add(Op))) {
>        Instr->setOperand(i, V);
>      } else {
>        success = false;
>
>
>
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