Implement the missing pieces needed to support libstdc++4.7's <atomic>:

__atomic_test_and_set, __atomic_clear, plus a pile of undocumented __GCC_*
predefined macros.

Implement library fallback for __atomic_is_lock_free and
__c11_atomic_is_lock_free, and implement __atomic_always_lock_free.

Contrary to their documentation, GCC's __atomic_fetch_add family don't
multiply the operand by sizeof(T) when operating on a pointer type.
libstdc++ relies on this quirk. Remove this handling for all but the
__c11_atomic_fetch_add and __c11_atomic_fetch_sub builtins.

Contrary to their documentation, __atomic_test_and_set and __atomic_clear
take a first argument of type 'volatile void *', not 'void *' or 'bool *',
and __atomic_is_lock_free and __atomic_always_lock_free have an argument
of type 'const volatile void *', not 'void *'.

With this change, libstdc++4.7's <atomic> passes libc++'s atomic test suite,
except for a couple of libstdc++ bugs and some cases where libc++'s test
suite tests for properties which implementations have latitude to vary.

llvm-svn: 154640

1 files changed, 40 insertions, 0 deletions

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index c1b9d57f09d..93d49b0563b 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -202,6 +202,20 @@ static void DefineExactWidthIntType(TargetInfo::IntType Ty,
                         ConstSuffix);
 }
 
+/// Get the value the ATOMIC_*_LOCK_FREE macro should have for a type with
+/// the specified properties.
+static const char *getLockFreeValue(unsigned TypeWidth, unsigned TypeAlign,
+                                    unsigned InlineWidth) {
+  // Fully-aligned, power-of-2 sizes no larger than the inline
+  // width will be inlined as lock-free operations.
+  if (TypeWidth == TypeAlign && (TypeWidth & (TypeWidth - 1)) == 0 &&
+      TypeWidth <= InlineWidth)
+    return "2"; // "always lock free"
+  // We cannot be certain what operations the lib calls might be
+  // able to implement as lock-free on future processors.
+  return "1"; // "sometimes lock free"
+}
+
 /// \brief Add definitions required for a smooth interaction between
 /// Objective-C++ automated reference counting and libstdc++ (4.2).
 static void AddObjCXXARCLibstdcxxDefines(const LangOptions &LangOpts, 
@@ -521,6 +535,32 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   else
     Builder.defineMacro("__GNUC_STDC_INLINE__");
 
+  // The value written by __atomic_test_and_set.
+  // FIXME: This is target-dependent.
+  Builder.defineMacro("__GCC_ATOMIC_TEST_AND_SET_TRUEVAL", "1");
+
+  // Used by libstdc++ to implement ATOMIC_<foo>_LOCK_FREE.
+  unsigned InlineWidthBits = TI.getMaxAtomicInlineWidth();
+#define DEFINE_LOCK_FREE_MACRO(TYPE, Type) \
+  Builder.defineMacro("__GCC_ATOMIC_" #TYPE "_LOCK_FREE", \
+                      getLockFreeValue(TI.get##Type##Width(), \
+                                       TI.get##Type##Align(), \
+                                       InlineWidthBits));
+  DEFINE_LOCK_FREE_MACRO(BOOL, Bool);
+  DEFINE_LOCK_FREE_MACRO(CHAR, Char);
+  DEFINE_LOCK_FREE_MACRO(CHAR16_T, Char16);
+  DEFINE_LOCK_FREE_MACRO(CHAR32_T, Char32);
+  DEFINE_LOCK_FREE_MACRO(WCHAR_T, WChar);
+  DEFINE_LOCK_FREE_MACRO(SHORT, Short);
+  DEFINE_LOCK_FREE_MACRO(INT, Int);
+  DEFINE_LOCK_FREE_MACRO(LONG, Long);
+  DEFINE_LOCK_FREE_MACRO(LLONG, LongLong);
+  Builder.defineMacro("__GCC_ATOMIC_POINTER_LOCK_FREE",
+                      getLockFreeValue(TI.getPointerWidth(0),
+                                       TI.getPointerAlign(0),
+                                       InlineWidthBits));
+#undef DEFINE_LOCK_FREE_MACRO
+
   if (LangOpts.NoInlineDefine)
     Builder.defineMacro("__NO_INLINE__");