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From f1ea62e93cba334828c427146cc2ca7718a9ffb3 Mon Sep 17 00:00:00 2001
From: Michal Gorny <mgorny@gentoo.org>
Date: Mon, 9 Jan 2017 20:54:20 +0000
Subject: [PATCH] [Frontend] Correct values of ATOMIC_*_LOCK_FREE to match
builtin
Correct the logic used to set ATOMIC_*_LOCK_FREE preprocessor macros not
to rely on the ABI alignment of types. Instead, just assume all those
types are aligned correctly by default since clang uses safe alignment
for _Atomic types even if the underlying types are aligned to a lower
boundary by default.
For example, the 'long long' and 'double' types on x86 are aligned to
32-bit boundary by default. However, '_Atomic long long' and '_Atomic
double' are aligned to 64-bit boundary, therefore satisfying
the requirements of lock-free atomic operations.
This fixes PR #19355 by correcting the value of
__GCC_ATOMIC_LLONG_LOCK_FREE on x86, and therefore also fixing
the assumption made in libc++ tests. This also fixes PR #30581 by
applying a consistent logic between the functions used to implement
both interfaces.
Differential Revision: https://reviews.llvm.org/D28213
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291477 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Frontend/InitPreprocessor.cpp | 10 ++++------
test/Sema/atomic-ops.c | 4 ----
2 files changed, 4 insertions(+), 10 deletions(-)
diff --git a/lib/Frontend/InitPreprocessor.cpp b/lib/Frontend/InitPreprocessor.cpp
index 17603ada11..4502c92499 100644
--- a/lib/Frontend/InitPreprocessor.cpp
+++ b/lib/Frontend/InitPreprocessor.cpp
@@ -286,12 +286,12 @@ static void DefineFastIntType(unsigned TypeWidth, bool IsSigned,
/// 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) {
+static const char *getLockFreeValue(unsigned TypeWidth, 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)
+ // Note: we do not need to check alignment since _Atomic(T) is always
+ // appropriately-aligned in clang.
+ if ((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.
@@ -881,7 +881,6 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
#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);
@@ -894,7 +893,6 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
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
}
diff --git a/test/Sema/atomic-ops.c b/test/Sema/atomic-ops.c
index 8ebf3eaed4..d3ebdf67db 100644
--- a/test/Sema/atomic-ops.c
+++ b/test/Sema/atomic-ops.c
@@ -14,11 +14,7 @@ _Static_assert(__GCC_ATOMIC_WCHAR_T_LOCK_FREE == 2, "");
_Static_assert(__GCC_ATOMIC_SHORT_LOCK_FREE == 2, "");
_Static_assert(__GCC_ATOMIC_INT_LOCK_FREE == 2, "");
_Static_assert(__GCC_ATOMIC_LONG_LOCK_FREE == 2, "");
-#ifdef __i386__
-_Static_assert(__GCC_ATOMIC_LLONG_LOCK_FREE == 1, "");
-#else
_Static_assert(__GCC_ATOMIC_LLONG_LOCK_FREE == 2, "");
-#endif
_Static_assert(__GCC_ATOMIC_POINTER_LOCK_FREE == 2, "");
_Static_assert(__c11_atomic_is_lock_free(1), "");
--
2.12.0
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