[PATCH] D60485: [AArch64] Add support for MTE intrinsics

Tim Northover via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Thu Apr 25 11:32:03 PDT 2019

t.p.northover accepted this revision.
t.p.northover added inline comments.
This revision is now accepted and ready to land.

Comment at: lib/CodeGen/CGBuiltin.cpp:7129-7131
+    // Although it is possible to supply a different return
+    // address (first arg) to this intrinsic, for now we set
+    // return address same as input address.
javed.absar wrote:
> t.p.northover wrote:
> > I think this should be fixed now.  It looks like technical debt from the fact that the instructions only fairly recently gained that feature after the intrinsics were implemented internally. There's no good way to justify the current semantics to someone unaware of that history.
> Not quite that really.  So the instruction did gain the feature recently like you mentioned. But the ACLE/intrinsics were designed and agreed upon after it and it was decided in ACLE discussions that the exta feature added complexity that need not be exposed at ACLE level yet. No big use case to justify complicating the ACLE MTE spec yet. Directly assembly can use that instruction though.
I think the ACLE decision was a mistake, but since it happened I withdraw this request. I expect (and hope) far more people will use these through ACLE than as compiler-specific builtins.



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