[llvm] [TableGen] Integrate TableGen-based macro fusion (PR #73115)

[Wang Pengcheng via llvm-commits]

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@@ -149,6 +151,10 @@ class CodeGenTarget {
 
   const CodeGenHwModes &getHwModes() const { return CGH; }
 
+  bool hasMacroFusion() const { return !MacroFusions.empty(); }
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wangpc-pp wrote:

This is to simplify `getMacroFusions().empty()`.

https://github.com/llvm/llvm-project/pull/73115