Representation of 'atomic load' and 'atomic store' in IR.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137170 91177308-0d34-0410-b5e6-96231b3b80d8
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@@ -1583,8 +1583,10 @@
<div class="doc_text">
<p>Atomic instructions (<a href="#i_cmpxchg"><code>cmpxchg</code></a>,
-<a href="#i_atomicrmw"><code>atomicrmw</code></a>, and
-<a href="#i_fence"><code>fence</code></a>) take an ordering parameter
+<a href="#i_atomicrmw"><code>atomicrmw</code></a>,
+<a href="#i_fence"><code>fence</code></a>,
+<a href="#i_load"><code>atomic load</code></a>, and
+<a href="#i_load"><code>atomic store</code></a>) take an ordering parameter
that determines which other atomic instructions on the same address they
<i>synchronize with</i>. These semantics are borrowed from Java and C++0x,
but are somewhat more colloquial. If these descriptions aren't precise enough,
@@ -1592,11 +1594,7 @@
treat these orderings somewhat differently since they don't take an address.
See that instruction's documentation for details.</p>
-<!-- FIXME Note atomic load+store here once those get added. -->
-
<dl>
-<!-- FIXME: unordered is intended to be used for atomic load and store;
-it isn't allowed for any instruction yet. -->
<dt><code>unordered</code></dt>
<dd>The set of values that can be read is governed by the happens-before
partial order. A value cannot be read unless some operation wrote it.
@@ -4572,8 +4570,8 @@
<h5>Syntax:</h5>
<pre>
- <result> = load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
- <result> = volatile load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
+ <result> = [volatile] load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
+ <result> = atomic [volatile] load <ty>* <pointer> [singlethread] <ordering>, align <alignment>
!<index> = !{ i32 1 }
</pre>
@@ -4588,6 +4586,19 @@
number or order of execution of this <tt>load</tt> with other <a
href="#volatile">volatile operations</a>.</p>
+<p>If the <code>load</code> is marked as <code>atomic</code>, it takes an extra
+ <a href="#ordering">ordering</a> and optional <code>singlethread</code>
+ argument. The <code>release</code> and <code>acq_rel</code> orderings are
+ not valid on <code>load</code> instructions. Atomic loads produce <a
+ href="#memorymodel">defined</a> 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. <code>align</code> 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. <code>!nontemporal</code> does not have any defined semantics
+ for atomic loads.</p>
+
<p>The optional constant <tt>align</tt> argument specifies the alignment of the
operation (that is, the alignment of the memory address). A value of 0 or an
omitted <tt>align</tt> argument means that the operation has the preferential
@@ -4631,8 +4642,8 @@
<h5>Syntax:</h5>
<pre>
- store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
- volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
+ [volatile] store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
+ atomic [volatile] store <ty> <value>, <ty>* <pointer> [singlethread] <ordering>, align <alignment> <i>; yields {void}</i>
</pre>
<h5>Overview:</h5>
@@ -4648,6 +4659,19 @@
order of execution of this <tt>store</tt> with other <a
href="#volatile">volatile operations</a>.</p>
+<p>If the <code>store</code> is marked as <code>atomic</code>, it takes an extra
+ <a href="#ordering">ordering</a> and optional <code>singlethread</code>
+ argument. The <code>acquire</code> and <code>acq_rel</code> orderings aren't
+ valid on <code>store</code> instructions. Atomic loads produce <a
+ href="#memorymodel">defined</a> 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. <code>align</code> 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. <code>!nontemporal</code> does not have any defined semantics
+ for atomic stores.</p>
+
<p>The optional constant "align" argument specifies the alignment of the
operation (that is, the alignment of the memory address). A value of 0 or an
omitted "align" argument means that the operation has the preferential
@@ -4730,9 +4754,6 @@
specifies that the fence only synchronizes with other fences in the same
thread. (This is useful for interacting with signal handlers.)</p>
-<p>FIXME: This instruction is a work in progress; until it is finished, use
- llvm.memory.barrier.
-
<h5>Example:</h5>
<pre>
fence acquire <i>; yields {void}</i>