[clang] [C++17] Support __GCC_[CON|DE]STRUCTIVE_SIZE (PR #89446)

via cfe-commits cfe-commits at lists.llvm.org
Fri Apr 19 12:59:59 PDT 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Aaron Ballman (AaronBallman)

<details>
<summary>Changes</summary>

These macros are used by STL implementations to support implementation of std::hardware_destructive_interference_size and std::hardware_constructive_interference_size

Fixes #<!-- -->60174

---
Full diff: https://github.com/llvm/llvm-project/pull/89446.diff


6 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+13) 
- (modified) clang/include/clang/Basic/TargetInfo.h (+5) 
- (modified) clang/lib/Frontend/InitPreprocessor.cpp (+7) 
- (modified) clang/test/Preprocessor/init-aarch64.c (+7-5) 
- (modified) clang/test/Preprocessor/init.c (+29-20) 
- (modified) clang/test/Preprocessor/predefined-win-macros.c (+4-2) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index aea8fda35bb29c..7414856fd6a03e 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -89,6 +89,19 @@ sections with improvements to Clang's support for those languages.
 C++ Language Changes
 --------------------
 
+C++17 Feature Support
+^^^^^^^^^^^^^^^^^^^^^
+- Clang now exposes ``__GCC_DESTRUCTIVE_SIZE`` and ``__GCC_CONSTRUCTIVE_SIZE``
+  predefined macros to support standard library implementations of
+  ``std::hardware_destructive_interference_size`` and
+  ``std::hardware_constructive_interference_size``, respectively. These macros
+  are predefined in all C and C++ language modes. These macros can be
+  overridden on the command line with ``-D``, if desired. The values the macros
+  expand to are not stable between releases of Clang and do not need to match
+  the values produced by GCC, so these macros should not be used from header
+  files because they may not be stable across multiple TUs (the values may vary
+  based on compiler version as well as CPU tuning). #GH60174
+
 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
index e1ef7454f01669..a7b112a41f1b99 100644
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -1792,6 +1792,11 @@ class TargetInfo : public TransferrableTargetInfo,
   /// Whether to support HIP image/texture API's.
   virtual bool hasHIPImageSupport() const { return true; }
 
+  /// The minimum offset between two objects to avoid false sharing.
+  virtual unsigned hardwareDestructiveInterferenceSize() const { return 64; }
+  // The maximum size of contiguous memory to promote true sharing.
+  virtual unsigned hardwareConstructiveInterferenceSize() const { return 64; }
+
 protected:
   /// Copy type and layout related info.
   void copyAuxTarget(const TargetInfo *Aux);
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 4f44c3b7b89d4d..b88cd86e09fa1e 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -1309,6 +1309,13 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
     Builder.defineMacro("__GCC_ATOMIC_TEST_AND_SET_TRUEVAL", "1");
   }
 
+  // GCC defines these macros in both C and C++ modes despite them being needed
+  // mostly for STL implementations in C++.
+  Builder.defineMacro("__GCC_DESTRUCTIVE_SIZE",
+                      Twine(TI.hardwareDestructiveInterferenceSize()));
+  Builder.defineMacro("__GCC_CONSTRUCTIVE_SIZE",
+                      Twine(TI.hardwareConstructiveInterferenceSize()));
+
   auto addLockFreeMacros = [&](const llvm::Twine &Prefix) {
     // Used by libc++ and libstdc++ to implement ATOMIC_<foo>_LOCK_FREE.
 #define DEFINE_LOCK_FREE_MACRO(TYPE, Type)                                     \
diff --git a/clang/test/Preprocessor/init-aarch64.c b/clang/test/Preprocessor/init-aarch64.c
index cf96870b27acb3..f0845985c9efc3 100644
--- a/clang/test/Preprocessor/init-aarch64.c
+++ b/clang/test/Preprocessor/init-aarch64.c
@@ -119,6 +119,8 @@
 // AARCH64-NEXT: #define __FP_FAST_FMA 1
 // AARCH64-NEXT: #define __FP_FAST_FMAF 1
 // AARCH64-NEXT: #define __GCC_ASM_FLAG_OUTPUTS__ 1
+// AARCH64-NEXT: #define __GCC_CONSTRUCTIVE_SIZE {{.+}}
+// AARCH64-NEXT: #define __GCC_DESTRUCTIVE_SIZE {{.+}}
 // AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
 // AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 1
 // AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
@@ -220,11 +222,11 @@
 // AARCH64-NEXT: #define __LONG_MAX__ 9223372036854775807L
 // AARCH64-NEXT: #define __LONG_WIDTH__ 64
 // AARCH64-NEXT: #define __LP64__ 1
-// AARCH64-NEXT: #define __MEMORY_SCOPE_DEVICE 1 
-// AARCH64-NEXT: #define __MEMORY_SCOPE_SINGLE 4 
-// AARCH64-NEXT: #define __MEMORY_SCOPE_SYSTEM 0 
-// AARCH64-NEXT: #define __MEMORY_SCOPE_WRKGRP 2 
-// AARCH64-NEXT: #define __MEMORY_SCOPE_WVFRNT 3 
+// AARCH64-NEXT: #define __MEMORY_SCOPE_DEVICE 1
+// AARCH64-NEXT: #define __MEMORY_SCOPE_SINGLE 4
+// AARCH64-NEXT: #define __MEMORY_SCOPE_SYSTEM 0
+// AARCH64-NEXT: #define __MEMORY_SCOPE_WRKGRP 2
+// AARCH64-NEXT: #define __MEMORY_SCOPE_WVFRNT 3
 // AARCH64-NEXT: #define __NO_INLINE__ 1
 // AARCH64-NEXT: #define __NO_MATH_ERRNO__ 1
 // AARCH64-NEXT: #define __OBJC_BOOL_IS_BOOL 0
diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
index c4a55efca6f712..2641fee940231f 100644
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -1,3 +1,10 @@
+// RUN: %clang_cc1 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix INTERFERENCE %s
+//
+// We purposefully do not test the values produced, only that the macros are
+// predefined to some value.
+// INTERFERENCE:#define __GCC_CONSTRUCTIVE_SIZE {{.+}}
+// INTERFERENCE:#define __GCC_DESTRUCTIVE_SIZE {{.+}}
+
 // RUN: %clang_cc1 -E -dM -x assembler-with-cpp < /dev/null | FileCheck -match-full-lines -check-prefix ASM %s
 //
 // ASM:#define __ASSEMBLER__ 1
@@ -1697,6 +1704,8 @@
 // WEBASSEMBLY-NEXT:#define __GCC_ATOMIC_SHORT_LOCK_FREE 2
 // WEBASSEMBLY-NEXT:#define __GCC_ATOMIC_TEST_AND_SET_TRUEVAL 1
 // WEBASSEMBLY-NEXT:#define __GCC_ATOMIC_WCHAR_T_LOCK_FREE 2
+// WEBASSEMBLY-NEXT:#define __GCC_CONSTRUCTIVE_SIZE {{.+}}
+// WEBASSEMBLY-NEXT:#define __GCC_DESTRUCTIVE_SIZE {{.+}}
 // WEBASSEMBLY-NEXT:#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
 // WEBASSEMBLY-NEXT:#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
 // WEBASSEMBLY-NEXT:#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
@@ -1806,11 +1815,11 @@
 // WEBASSEMBLY64-NEXT:#define __LONG_MAX__ 9223372036854775807L
 // WEBASSEMBLY64-NEXT:#define __LONG_WIDTH__ 64
 // WEBASSEMBLY64-NEXT:#define __LP64__ 1
-// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_DEVICE 1 
-// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_SINGLE 4 
-// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_SYSTEM 0 
-// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_WRKGRP 2 
-// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_WVFRNT 3 
+// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_DEVICE 1
+// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_SINGLE 4
+// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_SYSTEM 0
+// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_WRKGRP 2
+// WEBASSEMBLY-NEXT:#define __MEMORY_SCOPE_WVFRNT 3
 // WEBASSEMBLY-NEXT:#define __NO_INLINE__ 1
 // WEBASSEMBLY-NEXT:#define __NO_MATH_ERRNO__ 1
 // WEBASSEMBLY-NEXT:#define __OBJC_BOOL_IS_BOOL 0
@@ -2126,11 +2135,11 @@
 // AVR:#define __LDBL_MIN__ 1.17549435e-38L
 // AVR:#define __LONG_LONG_MAX__ 9223372036854775807LL
 // AVR:#define __LONG_MAX__ 2147483647L
-// AVR:#define __MEMORY_SCOPE_DEVICE 1 
-// AVR:#define __MEMORY_SCOPE_SINGLE 4 
-// AVR:#define __MEMORY_SCOPE_SYSTEM 0 
-// AVR:#define __MEMORY_SCOPE_WRKGRP 2 
-// AVR:#define __MEMORY_SCOPE_WVFRNT 3 
+// AVR:#define __MEMORY_SCOPE_DEVICE 1
+// AVR:#define __MEMORY_SCOPE_SINGLE 4
+// AVR:#define __MEMORY_SCOPE_SYSTEM 0
+// AVR:#define __MEMORY_SCOPE_WRKGRP 2
+// AVR:#define __MEMORY_SCOPE_WVFRNT 3
 // AVR:#define __NO_INLINE__ 1
 // AVR:#define __ORDER_BIG_ENDIAN__ 4321
 // AVR:#define __ORDER_LITTLE_ENDIAN__ 1234
@@ -2422,11 +2431,11 @@
 // RISCV32: #define __LITTLE_ENDIAN__ 1
 // RISCV32: #define __LONG_LONG_MAX__ 9223372036854775807LL
 // RISCV32: #define __LONG_MAX__ 2147483647L
-// RISCV32: #define __MEMORY_SCOPE_DEVICE 1 
-// RISCV32: #define __MEMORY_SCOPE_SINGLE 4 
-// RISCV32: #define __MEMORY_SCOPE_SYSTEM 0 
-// RISCV32: #define __MEMORY_SCOPE_WRKGRP 2 
-// RISCV32: #define __MEMORY_SCOPE_WVFRNT 3 
+// RISCV32: #define __MEMORY_SCOPE_DEVICE 1
+// RISCV32: #define __MEMORY_SCOPE_SINGLE 4
+// RISCV32: #define __MEMORY_SCOPE_SYSTEM 0
+// RISCV32: #define __MEMORY_SCOPE_WRKGRP 2
+// RISCV32: #define __MEMORY_SCOPE_WVFRNT 3
 // RISCV32: #define __NO_INLINE__ 1
 // RISCV32: #define __POINTER_WIDTH__ 32
 // RISCV32: #define __PRAGMA_REDEFINE_EXTNAME 1
@@ -2634,11 +2643,11 @@
 // RISCV64: #define __LONG_LONG_MAX__ 9223372036854775807LL
 // RISCV64: #define __LONG_MAX__ 9223372036854775807L
 // RISCV64: #define __LP64__ 1
-// RISCV64: #define __MEMORY_SCOPE_DEVICE 1 
-// RISCV64: #define __MEMORY_SCOPE_SINGLE 4 
-// RISCV64: #define __MEMORY_SCOPE_SYSTEM 0 
-// RISCV64: #define __MEMORY_SCOPE_WRKGRP 2 
-// RISCV64: #define __MEMORY_SCOPE_WVFRNT 3 
+// RISCV64: #define __MEMORY_SCOPE_DEVICE 1
+// RISCV64: #define __MEMORY_SCOPE_SINGLE 4
+// RISCV64: #define __MEMORY_SCOPE_SYSTEM 0
+// RISCV64: #define __MEMORY_SCOPE_WRKGRP 2
+// RISCV64: #define __MEMORY_SCOPE_WVFRNT 3
 // RISCV64: #define __NO_INLINE__ 1
 // RISCV64: #define __POINTER_WIDTH__ 64
 // RISCV64: #define __PRAGMA_REDEFINE_EXTNAME 1
diff --git a/clang/test/Preprocessor/predefined-win-macros.c b/clang/test/Preprocessor/predefined-win-macros.c
index b830dc39d477dd..14e2f584bd0938 100644
--- a/clang/test/Preprocessor/predefined-win-macros.c
+++ b/clang/test/Preprocessor/predefined-win-macros.c
@@ -3,7 +3,7 @@
 // RUN: %clang_cc1 %s -x c++ -E -dM -triple x86_64-pc-win32 -fms-extensions -fms-compatibility \
 // RUN:     -fms-compatibility-version=19.00 -std=c++14 -o - | FileCheck -match-full-lines %s --check-prefix=CHECK-MS64
 // RUN: %clang_cc1 %s -x c++ -E -dM -triple x86_64-pc-win32 -fms-extensions -fms-compatibility \
-// RUN:     -fms-compatibility-version=19.00 -std=c++14 -o - | grep GCC | count 5
+// RUN:     -fms-compatibility-version=19.00 -std=c++14 -o - | grep GCC | count 7
 // CHECK-MS64: #define _INTEGRAL_MAX_BITS 64
 // CHECK-MS64: #define _ISO_VOLATILE 1
 // CHECK-MS64: #define _MSC_EXTENSIONS 1
@@ -26,7 +26,7 @@
 // RUN: %clang_cc1 %s -x c++ -E -dM -triple i686-pc-win32 -fms-extensions -fms-compatibility \
 // RUN:     -fms-compatibility-version=19.00 -std=c++17 -o - | FileCheck -match-full-lines %s --check-prefix=CHECK-MS
 // RUN: %clang_cc1 %s -x c++ -E -dM -triple i686-pc-win32 -fms-extensions -fms-compatibility \
-// RUN:     -fms-compatibility-version=19.00 -std=c++17 -o - | grep GCC | count 5
+// RUN:     -fms-compatibility-version=19.00 -std=c++17 -o - | grep GCC | count 7
 // CHECK-MS: #define _INTEGRAL_MAX_BITS 64
 // CHECK-MS: #define _ISO_VOLATILE 1
 // CHECK-MS: #define _MSC_EXTENSIONS 1
@@ -39,6 +39,8 @@
 // CHECK-MS-NOT: GNU
 // CHECK-MS-NOT: GXX
 // CHECK-MS: #define __GCC_ASM_FLAG_OUTPUTS__ 1
+// CHECK-MS: #define __GCC_CONSTRUCTIVE_SIZE {{.+}}
+// CHECK-MS: #define __GCC_DESTRUCTIVE_SIZE {{.+}}
 // CHECK-MS: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
 // CHECK-MS: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
 // CHECK-MS: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1

``````````

</details>


https://github.com/llvm/llvm-project/pull/89446


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