[PATCH] D55290: [docs] Update llvm.loop metadata documentation.
Michael Kruse via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Dec 4 12:49:10 PST 2018
Meinersbur updated this revision to Diff 176694.
Meinersbur added a comment.
- Address @hfinkel's review
Repository:
rL LLVM
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D55290/new/
https://reviews.llvm.org/D55290
Files:
docs/LangRef.rst
Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -5081,33 +5081,28 @@
It is sometimes useful to attach information to loop constructs. Currently,
loop metadata is implemented as metadata attached to the branch instruction
-in the loop latch block. This type of metadata refer to a metadata node that is
-guaranteed to be separate for each loop. The loop identifier metadata is
-specified with the name ``llvm.loop``.
-
-The loop identifier metadata is implemented using a metadata that refers to
-itself to avoid merging it with any other identifier metadata, e.g.,
-during module linkage or function inlining. That is, each loop should refer
-to their own identification metadata even if they reside in separate functions.
-The following example contains loop identifier metadata for two separate loop
-constructs:
-
-.. code-block:: llvm
-
- !0 = !{!0}
- !1 = !{!1}
-
-The loop identifier metadata can be used to specify additional
-per-loop metadata. Any operands after the first operand can be treated
-as user-defined metadata. For example the ``llvm.loop.unroll.count``
-suggests an unroll factor to the loop unroller:
+in the loop latch block. The loop metadata node is an unordered list of
+other metadata nodes, each representing a property of the loop. Usually,
+the first item of the property node is a string. For example the
+``llvm.loop.unroll.count`` suggests an unroll factor to the loop
+unroller:
.. code-block:: llvm
br i1 %exitcond, label %._crit_edge, label %.lr.ph, !llvm.loop !0
...
- !0 = !{!0, !1}
- !1 = !{!"llvm.loop.unroll.count", i32 4}
+ !0 = distinct !{!0, !1, !2}
+ !1 = !{!"llvm.loop.unroll.enable"}
+ !2 = !{!"llvm.loop.unroll.count", i32 4}
+
+For legacy reasons, the first item of a loop metadata node must be a
+reference to itself. It was used to avoid collapsing of multiple loop
+metadata nodes into one. The 'distinct' keyword for loop metadata nodes
+is also not necessary anymore.
+
+Loop metadata nodes cannot be used as identifiers. They are neither
+necessarily persistent for the same loop through pass transformations
+nor unique to just one loop.
'``llvm.loop.vectorize``' and '``llvm.loop.interleave``'
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D55290.176694.patch
Type: text/x-patch
Size: 2344 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20181204/23b3e799/attachment.bin>
More information about the llvm-commits
mailing list