[PATCH] D132978: [IRTranslator] Using ZExt for extractelement indices.

[Peter Rong via Phabricator via llvm-commits]

Peter added inline comments.


================
Comment at: llvm/docs/LangRef.rst:9694-9695
 the position from which to extract the element. The index may be a
-variable of any integer type.
+variable of any integer type, and will be zero extended or truncated 
+depending on the target.
 
----------------
foad wrote:
> From a semantics point of view, I think all we need to say is that the value is "treated as unsigned" or words to that effect. I don't think we should mention extending here (and definitely not truncating which sounds like it could change the value!).
https://llvm.godbolt.org/z/Mszb7EvPe

The (unfortunate) fact that we are using `zextOrTrunc` already implies that we can change the value given a large index, even thou no one is doing it.
I see two ways out of this:

1. Explain in detail in the doc "when" truncation will happen or
2. Further change the doc so the index can only be i64, which would involve even more code change.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132978/new/

https://reviews.llvm.org/D132978