[PATCH] D122377: [PowerPC][Linux] Support 16-byte lock free atomics on pwr8 and up

[Eli Friedman via Phabricator via cfe-commits]

efriedma added inline comments.


================
Comment at: clang/lib/Basic/Targets/PPC.h:451
+      MaxAtomicPromoteWidth = 128;
+      MaxAtomicInlineWidth = 128;
+    }
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MaxAtomicPromoteWidth should not depend on whether quadword-atomics is present, only the target OS.  It determines the layout of `_Atomic(__int128_t)`.

(MaxAtomicInlineWidth is allowed to adjust as necessary.)


================
Comment at: clang/lib/Driver/ToolChains/Clang.cpp:2140
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("-ppc-quadword-atomics");
+  }
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Please avoid using "-mllvm" options like this; among other issues, it doesn't work with LTO.  If we need to indicate this, please use a function attribute in the IR.

(Yes, there are other cases where we translate flags to -mllvm options, but it's not something you should copy.)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122377/new/

https://reviews.llvm.org/D122377