[clang] [ARM] Introduce -mtp=auto and make it the default (PR #128728)

[Peter Smith via cfe-commits]

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@@ -580,6 +581,9 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
     Features.push_back("+read-tp-tpidruro");
   if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::TPIDRPRW)
     Features.push_back("+read-tp-tpidrprw");
+  if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::Auto
+      && isHardTPSupported(Triple) && !ForAS)
+    Features.push_back("+read-tp-tpidrprw");
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smithp35 wrote:

I think you mean `+read-tp-tpidruro` here as that is what GCC defaults to.

https://github.com/llvm/llvm-project/pull/128728