From 5d05ed1d1725f801b0d11ce2b2cc712484085cb0 Mon Sep 17 00:00:00 2001 From: Juergen Ributzka Date: Fri, 17 Jan 2014 22:24:35 +0000 Subject: [PATCH] Update LangRef to emphasize the difference between "coldcc" and "preserve_mostcc". llvm-svn: 199521 --- llvm/docs/LangRef.rst | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index 39948f4b083c..a76770063657 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -312,7 +312,8 @@ added in the future: so that the call does not break any live ranges in the caller side. This calling convention does not support varargs and requires the prototype of all callees to exactly match the prototype of the - function definition. + function definition. Furthermore the inliner doesn't consider such function + calls for inlining. "``cc 10``" - GHC convention This calling convention has been implemented specifically for use by the `Glasgow Haskell Compiler (GHC) `_. @@ -375,7 +376,13 @@ added in the future: that have a hot path and a cold path. The hot path is usually a small piece of code that doesn't many registers. The cold path might need to call out to another function and therefore only needs to preserve the caller-saved - registers, which haven't already been saved by the caller. + registers, which haven't already been saved by the caller. The + `PreserveMost` calling convention is very similar to the `cold` calling + convention in terms of caller/callee-saved registers, but they are used for + different types of function calls. `coldcc` is for function calls that are + rarely executed, whereas `preserve_mostcc` function calls are intended to be + on the hot path and definitely executed a lot. Furthermore `preserve_mostcc` + doesn't prevent the inliner from inlining the function call. This calling convention will be used by a future version of the ObjectiveC runtime and should therefore still be considered experimental at this time.