[IR] Add support for floating pointer atomic loads and stores
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
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 72c0a31..f8d87da 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -6844,12 +6844,12 @@
``release`` and ``acq_rel`` orderings are not valid on ``load``
instructions. Atomic loads produce :ref:`defined <memmodel>` results
when they may see multiple atomic stores. The type of the pointee must
-be an integer type whose bit width is a power of two greater than or
-equal to eight and less than or equal to a target-specific size limit.
-``align`` must be explicitly specified on atomic loads, and the load has
-undefined behavior if the alignment is not set to a value which is at
-least the size in bytes of the pointee. ``!nontemporal`` does not have
-any defined semantics for atomic loads.
+be an integer or floating point type whose bit width is a power of two,
+greater than or equal to eight, and less than or equal to a
+target-specific size limit. ``align`` must be explicitly specified on
+atomic loads, and the load has undefined behavior if the alignment is
+not set to a value which is at least the size in bytes of the pointee.
+``!nontemporal`` does not have any defined semantics for atomic loads.
The optional constant ``align`` argument specifies the alignment of the
operation (that is, the alignment of the memory address). A value of 0
@@ -6969,12 +6969,13 @@
``acquire`` and ``acq_rel`` orderings aren't valid on ``store``
instructions. Atomic loads produce :ref:`defined <memmodel>` results
when they may see multiple atomic stores. The type of the pointee must
-be an integer type whose bit width is a power of two greater than or
-equal to eight and less than or equal to a target-specific size limit.
-``align`` must be explicitly specified on atomic stores, and the store
-has undefined behavior if the alignment is not set to a value which is
-at least the size in bytes of the pointee. ``!nontemporal`` does not
-have any defined semantics for atomic stores.
+be an integer or floating point type whose bit width is a power of two,
+greater than or equal to eight, and less than or equal to a
+target-specific size limit. ``align`` must be explicitly specified
+on atomic stores, and the store has undefined behavior if the alignment
+is not set to a value which is at least the size in bytes of the
+pointee. ``!nontemporal`` does not have any defined semantics for
+atomic stores.
The optional constant ``align`` argument specifies the alignment of the
operation (that is, the alignment of the memory address). A value of 0