Today, we do not allow cmpxchg operations with pointer arguments. We require the frontend to insert ptrtoint casts and do the cmpxchg in integers. While correct, this is problematic from a couple of perspectives:
1) It makes the IR harder to analyse (for instance, it make capture tracking overly conservative)
2) It pushes work onto the frontend authors for no real gain
This patch implements the simplest form of IR support. As we did with floating point loads and stores, we teach AtomicExpand to convert back to the old representation. This prevents us needing to change all backends in a single lock step change. Over time, we can migrate each backend to natively selecting the pointer type. In the meantime, we get the advantages of a cleaner IR representation without waiting for the backend changes.
Differential Revision: http://reviews.llvm.org/D17413
llvm-svn: 261281
This patch allows atomic loads and stores of floating point to be specified in the IR and adds an adapter to allow them to be lowered via existing backend support for bitcast-to-equivalent-integer idiom.
Previously, the only way to specify a atomic float operation was to bitcast the pointer to a i32, load the value as an i32, then bitcast to a float. At it's most basic, this patch simply moves this expansion step to the point we start lowering to the backend.
This patch does not add canonicalization rules to convert the bitcast idioms to the appropriate atomic loads. I plan to do that in the future, but for now, let's simply add the support. I'd like to get instruction selection working through at least one backend (x86-64) without the bitcast conversion before canonicalizing into this form.
Similarly, I haven't yet added the target hooks to opt out of the lowering step I added to AtomicExpand. I figured it would more sense to add those once at least one backend (x86) was ready to actually opt out.
As you can see from the included tests, the generated code quality is not great. I plan on submitting some patches to fix this, but help from others along that line would be very welcome. I'm not super familiar with the backend and my ramp up time may be material.
Differential Revision: http://reviews.llvm.org/D15471
llvm-svn: 255737
Summary: Divide the primitive size in bits by eight so the initial load's alignment is in bytes as expected. Tested with the included unit test.
Reviewers: rengolin, jfb
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D11804
llvm-svn: 244229
Philip Reames