Wordsmith the semantics of invariant.load

[sanjoy]

Summary

Don't phrase the semantics in terms of the optimizer. Instead have a
more straightforward execution based semantic.

[skatkov]

I'm ok with this change however I think that "executed" term may be somehow specified more. May be "executed at runtime" ?

[sanjoy]

In D63439#1547619, @skatkov wrote:

I'm ok with this change however I think that "executed" term may be somehow specified more. May be "executed at runtime" ?

Not trying to sound flippant here, but what other ways are there to execute the load?

[skatkov]

In D63439#1547659, @sanjoy wrote:

In D63439#1547619, @skatkov wrote:

I'm ok with this change however I think that "executed" term may be somehow specified more. May be "executed at runtime" ?

Not trying to sound flippant here, but what other ways are there to execute the load?

I do not know :)

[ebrevnov]

LGTM

docs/LangRef.rst

 metadata on the instruction tells the optimizer and code generator
 that this load is not expected to be reused in the cache. The code
 generator may select special instructions to save cache bandwidth, such
 as the ``MOVNT`` instruction on x86.
 
 The optional ``!invariant.load`` metadata must reference a single
 metadata name ``<index>`` corresponding to a metadata node with no
 entries. If a load instruction tagged with the ``!invariant.load``
-metadata is executed, the optimizer may assume the memory location
-referenced by the load contains the same value at all points in the
-program where the memory location is known to be dereferenceable;
-otherwise, the behavior is undefined.
+metadata is executed, the memory location referenced by the load has
+to contain the same value at all points in the program where the
+memory location is dereferenceable; otherwise, the behavior is
+undefined.
 
 The optional ``!invariant.group`` metadata must reference a single metadata name
  ``<index>`` corresponding to a metadata node with no entries.
  See ``invariant.group`` metadata.
 
 The optional ``!nonnull`` metadata must reference a single
 metadata name ``<index>`` corresponding to a metadata node with no
 entries. The existence of the ``!nonnull`` metadata on the