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author | Renato Golin <renato.golin@linaro.org> | 2014-03-26 14:01:32 +0000 |
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committer | Renato Golin <renato.golin@linaro.org> | 2014-03-26 14:01:32 +0000 |
commit | 58839f43de03c894c3398ba2f7429c3ba82c96c1 (patch) | |
tree | 87aaf33c8ea1753977004fca30253065b725feac /docs/LangRef.rst | |
parent | cee1aecc57161f75c6d6af7c1f2ea6758bdd6b02 (diff) | |
download | llvm-58839f43de03c894c3398ba2f7429c3ba82c96c1.tar.gz llvm-58839f43de03c894c3398ba2f7429c3ba82c96c1.tar.bz2 llvm-58839f43de03c894c3398ba2f7429c3ba82c96c1.tar.xz |
Change @llvm.clear_cache default to call rt-lib
After some discussion on IRC, emitting a call to the library function seems
like a better default, since it will move from a compiler internal error to
a linker error, that the user can work around until LLVM is fixed.
I'm also adding a note on the responsibility of the user to confirm that
the cache was cleared on platforms where nothing is done.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204806 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/LangRef.rst')
-rw-r--r-- | docs/LangRef.rst | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/docs/LangRef.rst b/docs/LangRef.rst index d18d4ebac9..1a6549a15d 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -6964,10 +6964,20 @@ 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. +altogether when they are (ex. x86_64). Some targets can lower these +directly into special instructions, if they have it. + +The default behaviour is to emit a call to ``__clear_cache``, so in +case a target doesn't support it, the user gets a linker error rather +than a compiler internal error. It also provides a work around to +the user (implement an empty function called ``__clear_cache``) while +LLVM doesn't implement it in the target's back-end. + +Please note that the caller is responsible for ensuring the cache +is actually cleared. This is most important in targets that don't +need to flush the cache directly (ex. x86_64) and could potentially +still execute old instructions while the cache is not cleared. LLVM +will *not* insert nops or busy-wait sequences. Standard C Library Intrinsics ----------------------------- |