[llvm-branch-commits] [clang] [clang] Add clang::nooutline Attribute (PR #163666)

[Erich Keane via llvm-branch-commits]

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@@ -862,6 +862,36 @@ with ``__noinline__`` defined as a macro as ``__attribute__((noinline))``.
   }];
 }
 
+def NoOutlineDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+This function attribute suppresses outlining from the annotated function.
+
+Outlining is the process where common parts of separate functions are extracted
+into a separate function (or assembly snippet), and calls to that function or
+snippet are inserted in the original functions. In this way, it can be seen as
+the opposite of inlining. It can help to reduce code size.
+
+.. code-block:: c
+
+  [[clang::nooutline]] int x1(int y) {
+    int z = COMPLEX_MACRO(y); // Not outlined
+    return z + const1;
+  }
+
+  int x2(int y) {
+    int z = COMPLEX_MACRO(y); // May be outlined
+    return z * const2;
+  }
+
+  int x3(int y) {
+    int z = COMPLEX_MACRO(y); // May be outlined
+    reutrn z / const3;
+  }
+
+  }];
+}
----------------
erichkeane wrote:

Can you explain why one would not want this to happen?  Perhaps a quick example?  And can you show a psuedo-code version of x2/x3 (though I'd probably suggest only a single-one of those examples, they aren't unique enough to have 2) as to what it might look like as an 'outlined' version?

https://github.com/llvm/llvm-project/pull/163666