[OPENMP] Codegen for 'atomic capture'.

Adds codegen for 'atomic capture' constructs with the following forms of expressions/statements:

v = x binop= expr;
v = x++;
v = ++x;
v = x--;
v = --x;
v = x = x binop expr;
v = x = expr binop x;
{v = x; x = binop= expr;}
{v = x; x++;}
{v = x; ++x;}
{v = x; x--;}
{v = x; --x;}
{x = x binop expr; v = x;}
{x binop= expr; v = x;}
{x++; v = x;}
{++x; v = x;}
{x--; v = x;}
{--x; v = x;}
{x = x binop expr; v = x;}
{x = expr binop x; v = x;}
{v = x; x = expr;}
If x and expr are integer and binop is associative or x is a LHS in a RHS of the assignment expression, and atomics are allowed for type of x on the target platform atomicrmw instruction is emitted.
Otherwise compare-and-swap sequence is emitted.
Update of 'v' is not required to be be atomic with respect to the read or write of the 'x'.

bb:
...
atomic load <x>
cont:
<expected> = phi [ <x>, label %bb ], [ <new_failed>, %cont ]
<desired> = <expected> binop <expr>
<res> = cmpxchg atomic &<x>, desired, expected
<new_failed> = <res>.field1;
br <res>field2, label %exit, label %cont
exit:
atomic store <old/new x>, <v>
...
Differential Revision: http://reviews.llvm.org/D9049

llvm-svn: 235573

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 0d3fa07..87b7a2bc 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2063,7 +2063,9 @@ public:
   /// \param AO Atomic ordering of the generated atomic instructions.
   /// \param CommonGen Code generator for complex expressions that cannot be
   /// expressed through atomicrmw instruction.
-  void EmitOMPAtomicSimpleUpdateExpr(
+  /// \returns <true, OldAtomicValue> if simple 'atomicrmw' instruction was
+  /// generated, <false, RValue::get(nullptr)> otherwise.
+  std::pair<bool, RValue> EmitOMPAtomicSimpleUpdateExpr(
       LValue X, RValue E, BinaryOperatorKind BO, bool IsXLHSInRHSPart,
       llvm::AtomicOrdering AO, SourceLocation Loc,
       const llvm::function_ref<RValue(RValue)> &CommonGen);