Initial implementation of __atomic_is_lock_free. The input is the size of an atomic type rather than an atomic type itself just to save some implementation pain; I can change that if it seems worthwhile.
I think this is the last hook needed for <atomic> besides defines for ATOMIC_CHAR_LOCK_FREE and friends.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142281 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Basic/Builtins.def b/include/clang/Basic/Builtins.def
index e5690c1..63de4e5 100644
--- a/include/clang/Basic/Builtins.def
+++ b/include/clang/Basic/Builtins.def
@@ -598,6 +598,7 @@
BUILTIN(__atomic_fetch_xor, "v.", "t")
BUILTIN(__atomic_thread_fence, "vi", "n")
BUILTIN(__atomic_signal_fence, "vi", "n")
+BUILTIN(__atomic_is_lock_free, "iz", "n")
// Non-overloaded atomic builtins.
BUILTIN(__sync_synchronize, "v.", "n")
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 3c21dc4..c3cc78e 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -1344,6 +1344,50 @@
}
return Error(E->getLocStart(), diag::note_invalid_subexpr_in_ice, E);
+
+ case Builtin::BI__atomic_is_lock_free: {
+ APSInt SizeVal;
+ if (!EvaluateInteger(E->getArg(0), SizeVal, Info))
+ return false;
+
+ // For __atomic_is_lock_free(sizeof(_Atomic(T))), if the size is a power
+ // of two less than the maximum inline atomic width, we know it is
+ // lock-free. If the size isn't a power of two, or greater than the
+ // maximum alignment where we promote atomics, we know it is not lock-free
+ // (at least not in the sense of atomic_is_lock_free). Otherwise,
+ // the answer can only be determined at runtime; for example, 16-byte
+ // atomics have lock-free implementations on some, but not all,
+ // x86-64 processors.
+
+ // Check power-of-two.
+ CharUnits Size = CharUnits::fromQuantity(SizeVal.getZExtValue());
+ if (!Size.isPowerOfTwo())
+#if 0
+ // FIXME: Suppress this folding until the ABI for the promotion width
+ // settles.
+ return Success(0, E);
+#else
+ return Error(E->getLocStart(), diag::note_invalid_subexpr_in_ice, E);
+#endif
+
+#if 0
+ // Check against promotion width.
+ // FIXME: Suppress this folding until the ABI for the promotion width
+ // settles.
+ unsigned PromoteWidthBits =
+ Info.Ctx.getTargetInfo().getMaxAtomicPromoteWidth();
+ if (Size > Info.Ctx.toCharUnitsFromBits(PromoteWidthBits))
+ return Success(0, E);
+#endif
+
+ // Check against inlining width.
+ unsigned InlineWidthBits =
+ Info.Ctx.getTargetInfo().getMaxAtomicInlineWidth();
+ if (Size <= Info.Ctx.toCharUnitsFromBits(InlineWidthBits))
+ return Success(1, E);
+
+ return Error(E->getLocStart(), diag::note_invalid_subexpr_in_ice, E);
+ }
}
}
diff --git a/test/CodeGen/atomic-ops.c b/test/CodeGen/atomic-ops.c
index e2904cf..0ae70b1 100644
--- a/test/CodeGen/atomic-ops.c
+++ b/test/CodeGen/atomic-ops.c
@@ -75,3 +75,9 @@
// CHECK: atomicrmw xchg i32*
return __atomic_exchange(c, (X){2}, memory_order_seq_cst);
}
+
+int lock_free() {
+ // CHECK: @lock_free
+ // CHECK: ret i32 1
+ return __atomic_is_lock_free(sizeof(_Atomic(int)));
+}
\ No newline at end of file
