[PATCH] D55866: [DAGCombiner] allow narrowing of add followed by truncate

Wed Dec 19 06:45:16 PST 2018

spatel added a comment.

In D55866#1336120 <https://reviews.llvm.org/D55866#1336120>, @andreadb wrote:

> From an x86 point of view, this change looks good.
>
> At some point, we should address the poor codegen from `test/CodeGen/X86/pr32345.ll`. Maybe you could raise a bug for it.

I don't think it's worth the effort if we look at the background for this test; the intent was to check for a crash with *unoptimized* code:
https://bugs.llvm.org/show_bug.cgi?id=32345
rL298923 <https://reviews.llvm.org/rL298923>
...so the test includes CSE values that the DAG never expects to encounter. I think the optimized RUN was just added for completeness/sanity. The whole thing is folded to 'unreachable' in IR.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55866/new/

https://reviews.llvm.org/D55866