[PATCH] D135142: Use TI.hasBuiltinAtomic() when setting ATOMIC_*_LOCK_FREE values. NFCI

[Alexander Richardson via Phabricator via cfe-commits]

arichardson created this revision.
arichardson added reviewers: rprichard, efriedma, hfinkel.
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arichardson requested review of this revision.
Herald added a project: clang.
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I noticed that the values for __{CLANG,GCC}_ATOMIC_POINTER_LOCK_FREE were
incorrectly set to 1 instead of two in downstream CHERI targets because
pointers are handled specially there. While fixing this downstream, I
noticed that the existing code could be refactored to use
TargetInfo::hasBuiltinAtomic instead of repeating the almost identical
logic. In theory there could be a difference here since hasBuiltinAtomic() also
returns true for types less than 1 char in size, but since
InitializePredefinedMacros() never passes such a value this change should
not introduce any functional changes.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135142

Files:
  clang/lib/Frontend/InitPreprocessor.cpp


Index: clang/lib/Frontend/InitPreprocessor.cpp
===================================================================
--- clang/lib/Frontend/InitPreprocessor.cpp
+++ clang/lib/Frontend/InitPreprocessor.cpp
@@ -298,12 +298,12 @@
 
 /// Get the value the ATOMIC_*_LOCK_FREE macro should have for a type with
 /// the specified properties.
-static const char *getLockFreeValue(unsigned TypeWidth, unsigned InlineWidth) {
+static const char *getLockFreeValue(unsigned TypeWidth, const TargetInfo &TI) {
   // Fully-aligned, power-of-2 sizes no larger than the inline
   // width will be inlined as lock-free operations.
   // Note: we do not need to check alignment since _Atomic(T) is always
   // appropriately-aligned in clang.
-  if ((TypeWidth & (TypeWidth - 1)) == 0 && TypeWidth <= InlineWidth)
+  if (TI.hasBuiltinAtomic(TypeWidth, TypeWidth))
     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.
@@ -1149,11 +1149,9 @@
 
   auto addLockFreeMacros = [&](const llvm::Twine &Prefix) {
     // Used by libc++ and libstdc++ to implement ATOMIC_<foo>_LOCK_FREE.
-    unsigned InlineWidthBits = TI.getMaxAtomicInlineWidth();
 #define DEFINE_LOCK_FREE_MACRO(TYPE, Type)                                     \
   Builder.defineMacro(Prefix + #TYPE "_LOCK_FREE",                             \
-                      getLockFreeValue(TI.get##Type##Width(),                  \
-                                       InlineWidthBits));
+                      getLockFreeValue(TI.get##Type##Width(), TI));
     DEFINE_LOCK_FREE_MACRO(BOOL, Bool);
     DEFINE_LOCK_FREE_MACRO(CHAR, Char);
     if (LangOpts.Char8)
@@ -1166,8 +1164,7 @@
     DEFINE_LOCK_FREE_MACRO(LONG, Long);
     DEFINE_LOCK_FREE_MACRO(LLONG, LongLong);
     Builder.defineMacro(Prefix + "POINTER_LOCK_FREE",
-                        getLockFreeValue(TI.getPointerWidth(0),
-                                         InlineWidthBits));
+                        getLockFreeValue(TI.getPointerWidth(0), TI));
 #undef DEFINE_LOCK_FREE_MACRO
   };
   addLockFreeMacros("__CLANG_ATOMIC_");


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