https://bugs.llvm.org/show_bug.cgi?id=51823
Bug ID: 51823
Summary: llvm.aarch64.ldxr incompatible with opaque pointers
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: AArch64
Assignee: unassignedb...@nondot.org
Reporter: nikita....@gmail.com
CC: arnaud.degrandmai...@arm.com,
llvm-bugs@lists.llvm.org, smithp...@googlemail.com,
ties.st...@arm.com
Blocks: 46673
The AArch64 ldxr/ldxar/stxr/stlxr family of intrinsics currently works like
this:
call i64 @llvm.aarch64.ldxr.p0i8(i8* %addr)
The return value is always i64, and the size of the loaded/stored value is
determined by the pointer element type of the address.
To support opaque pointers, this could be changes in two ways. We could keep
the current approach and require an elementtype attribute:
call i64 @llvm.aarch64.ldxr.p0i8(i8* elementtype(i8) %addr)
Or we could change the definition of the intrinsic to return the loaded type,
rather than i64:
call i8 @llvm.aarch64.ldxr.i8.p0i8(i8* %addr)
The latter variant looks preferable to me. However, I think that needs some
significant changes to how these are lowered/selected. I tried to work on this,
but didn't get far
(https://gist.github.com/nikic/9b6d48d89d4b6e735d4f100e18c9b08a).
Referenced Bugs:
https://bugs.llvm.org/show_bug.cgi?id=46673
[Bug 46673] Remove pointer element types from the IR
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