Promote atomic type sizes up to a power of two, capped by
MaxAtomicPromoteWidth. Fix a ton of terrible bugs with
_Atomic types and (non-intrinsic-mediated) loads and stores
thereto.
llvm-svn: 176658
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index db1aa1a..4580424 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1602,18 +1602,21 @@
}
case Type::Atomic: {
+ // Start with the base type information.
std::pair<uint64_t, unsigned> Info
= getTypeInfo(cast<AtomicType>(T)->getValueType());
Width = Info.first;
Align = Info.second;
- if (Width != 0 && Width <= Target->getMaxAtomicPromoteWidth() &&
- llvm::isPowerOf2_64(Width)) {
- // We can potentially perform lock-free atomic operations for this
- // type; promote the alignment appropriately.
- // FIXME: We could potentially promote the width here as well...
- // is that worthwhile? (Non-struct atomic types generally have
- // power-of-two size anyway, but structs might not. Requires a bit
- // of implementation work to make sure we zero out the extra bits.)
+
+ // If the size of the type doesn't exceed the platform's max
+ // atomic promotion width, make the size and alignment more
+ // favorable to atomic operations:
+ if (Width != 0 && Width <= Target->getMaxAtomicPromoteWidth()) {
+ // Round the size up to a power of 2.
+ if (!llvm::isPowerOf2_64(Width))
+ Width = llvm::NextPowerOf2(Width);
+
+ // Set the alignment equal to the size.
Align = static_cast<unsigned>(Width);
}
}