bcraig added inline comments. ================ Comment at: lib/Frontend/InitPreprocessor.cpp:305 @@ +304,3 @@ + if (TypeWidth == TypeAlign && (TypeWidth & (TypeWidth - 1)) == 0 && + TypeWidth <= InlineWidth) + return Always; ---------------- jyknight wrote: > jfb wrote: > > bcraig wrote: > > > On some targets (like Hexagon), 4-byte values are cheap to inline, but > > > 1-byte values are not. Clang is spotty about checking this, but > > > TargetInfo::hasBuiltinAtomic seems like the right function to ask, if you > > > have access to it. > > You're commenting on: > > ``` > > if (TypeWidth == TypeAlign && (TypeWidth & (TypeWidth - 1)) == 0 && > > TypeWidth <= InlineWidth) > > ``` > > ? > > > > Are you asking for a separate change, or for a change to my patch? > That issue in clang's purview in any case; if hexagon wants to lower a 1-byte > cmpxchg to a compiler runtime function, it should do so in its backend. I am asking for a change to this patch. Don't assume that all widths smaller than some value are inline-able and lock free, because that may not be the case. A 4 byte cmpxchg could be lock free, while a 1 byte cmpxchg may not be lock free.
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