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[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.

Reviewed By: hfinkel, efriedma

Differential Revision: https://reviews.llvm.org/D28213
This commit is contained in:
Ryan Prichard 2022-07-21 13:09:48 -07:00
parent 408a2638fd
commit 02a25279ae
3 changed files with 7 additions and 13 deletions
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10
clang/lib/Frontend/InitPreprocessor.cpp
View File

@ -298,12 +298,12 @@ 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.
@ -1142,7 +1142,6 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
#define DEFINE_LOCK_FREE_MACRO(TYPE, Type) \
Builder.defineMacro(Prefix + #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);
@ -1157,7 +1156,6 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
DEFINE_LOCK_FREE_MACRO(LLONG, LongLong);
Builder.defineMacro(Prefix + "POINTER_LOCK_FREE",
getLockFreeValue(TI.getPointerWidth(0),
TI.getPointerAlign(0),
InlineWidthBits));
#undef DEFINE_LOCK_FREE_MACRO
};

6
clang/test/Preprocessor/init-x86.c
View File

@ -185,9 +185,9 @@
// I386:#define __i386__ 1
// I386:#define i386 1
// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN32 %s
// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-CXX -check-prefix I386-LINUX-ALIGN32 %s
// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 -malign-double < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN64 %s
// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu i486 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN32 %s
// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN64 %s
// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN64 -check-prefix I386-LINUX-CXX %s
//
// I386-LINUX-NOT:#define _LP64
// I386-LINUX:#define __BIGGEST_ALIGNMENT__ 16

4
clang/test/Sema/atomic-ops.c
View File

@ -33,11 +33,7 @@ _Static_assert(__GCC_ATOMIC_INT_LOCK_FREE == 2, "");
_Static_assert(__GCC_ATOMIC_INT_LOCK_FREE == __CLANG_ATOMIC_INT_LOCK_FREE, "");
_Static_assert(__GCC_ATOMIC_LONG_LOCK_FREE == 2, "");
_Static_assert(__GCC_ATOMIC_LONG_LOCK_FREE == __CLANG_ATOMIC_LONG_LOCK_FREE, "");
#ifdef __i386__
_Static_assert(__GCC_ATOMIC_LLONG_LOCK_FREE == 1, "");
#else
_Static_assert(__GCC_ATOMIC_LLONG_LOCK_FREE == 2, "");
#endif
_Static_assert(__GCC_ATOMIC_LLONG_LOCK_FREE == __CLANG_ATOMIC_LLONG_LOCK_FREE, "");
_Static_assert(__GCC_ATOMIC_POINTER_LOCK_FREE == 2, "");
_Static_assert(__GCC_ATOMIC_POINTER_LOCK_FREE == __CLANG_ATOMIC_POINTER_LOCK_FREE, "");