Add @llvm.clear_cache builtin

Implementing the LLVM part of the call to __builtin___clear_cache
which translates into an intrinsic @llvm.clear_cache and is lowered
by each target, either to a call to __clear_cache or nothing at all
incase the caches are unified.

Updating LangRef and adding some tests for the implemented architectures.
Other archs will have to implement the method in case this builtin
has to be compiled for it, since the default behaviour is to bail
unimplemented.

A Clang patch is required for the builtin to be lowered into the
llvm intrinsic. This will be done next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204802 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 30 insertions, 0 deletions

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index c959f56ef1..d18d4ebac9 100644
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -6939,6 +6939,36 @@ is lowered to a constant 0.
 Note that runtime support may be conditional on the privilege-level code is
 running at and the host platform.
 
+'``llvm.clear_cache``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare void @llvm.clear_cache(i8*, i8*)
+
+Overview:
+"""""""""
+
+The '``llvm.clear_cache``' intrinsic provides access to the systemcall
+that flushes the cache at the range specified. Some targets need this
+to specifically flush the instruction cache when executable data changes
+in memory (self-modifying code). Other targets have unified intruction
+and data cache, so they don't need any calls.
+
+Semantics:
+""""""""""
+
+When directly supported, this intrinsic will either return a call to
+the appropriate cache clearing system call (usually ``__clear_cache``)
+when the caches are not unified (ARM, Mips) or just remove the call
+altogether when they are (ex. x86_64).
+
+Targets must implement it directly to have either behaviour, as the
+default is to bail with "Not Implemented" message.
+
 Standard C Library Intrinsics
 -----------------------------