[clang] [clang][Driver] Fix triple config loading for clang-cl (PR #111397)

[via cfe-commits]

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@@ -1286,6 +1299,16 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
           appendOneArg(Args, Opt, nullptr);
         }
     }
+
+    // The config file may have changed the architecture so apply it.
+    if (HasConfigFile && Args.hasArg(options::OPT__SLASH_arm64EC)) {
+      llvm::Triple T(TargetTriple);
+      if (T.getArch() != llvm::Triple::aarch64 ||
+          T.getSubArch() != llvm::Triple::AArch64SubArch_arm64ec) {
+        T.setArch(llvm::Triple::aarch64, llvm::Triple::AArch64SubArch_arm64ec);
+        TargetTriple = T.str();
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zmodem wrote:

The PR description only mentions moving the default triple calculation earlier, but not this part.

The config file can presumably change many things, so why does the target triple need special handling? Also what about flags that affect x86 vs. x86_64 (-m32 and -m64), do we need to handle those too?

https://github.com/llvm/llvm-project/pull/111397