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| author | Stephen Lin <stephenwlin@gmail.com> | 2013-04-20 05:14:40 +0000 |
|---|---|---|
| committer | Stephen Lin <stephenwlin@gmail.com> | 2013-04-20 05:14:40 +0000 |
| commit | 456ca048af35163b9f52187e92a23ee0a9f059e8 (patch) | |
| tree | f7b4d4711424b927d5b323a9e4ef4d97742beeb4 /docs | |
| parent | 5c34e08b9fff9d4df2421e4f41ff15b85f638dd1 (diff) | |
Add CodeGen support for functions that always return arguments via a new parameter attribute 'returned', which is taken advantage of in target-independent tail call opportunity detection and in ARM call lowering (when placed on an integral first parameter).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179925 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/LangRef.rst | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/docs/LangRef.rst b/docs/LangRef.rst index 905053fef0..7dafbb9877 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -719,7 +719,17 @@ Currently, only the following parameter attributes are defined: ``nest`` This indicates that the pointer parameter can be excised using the :ref:`trampoline intrinsics <int_trampoline>`. This is not a valid - attribute for return values. + attribute for return values and can only be applied to one parameter. + +``returned`` + This indicates that the value of the function always returns the value + of the parameter as its return value. This is an optimization hint to + the code generator when generating the caller, allowing tail call + optimization and omission of register saves and restores in some cases; + it is not checked or enforced when generating the callee. The parameter + and the function return type must be valid operands for the + :ref:`bitcast instruction <i_bitcast>`. This is not a valid attribute for + return values and can only be applied to one parameter. .. _gc: |