[clang] [CIR] Enable x86_64 calling-convention lowering by default (PR #215026)

[Adam Smith via cfe-commits]

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@@ -423,9 +423,10 @@ class FrontendOptions {
   LLVM_PREFERRED_TYPE(bool)
   unsigned ClangIREnableIdiomRecognizer : 1;
 
-  /// Enable Clang IR (CIR) calling-convention lowering
+  /// Run the Clang IR (CIR) calling-convention lowering pass.  A no-op on
+  /// targets whose calling convention is not yet implemented.
   LLVM_PREFERRED_TYPE(bool)
-  unsigned ClangIREnableCallConvLowering : 1;
+  unsigned ClangIRCallConvLowering : 1;
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adams381 wrote:

After our discussion offline, I will open a new PR to address these after this merges.

https://github.com/llvm/llvm-project/pull/215026