From 7020f255b1807704e0dfc5a42f3016b0b940327b Mon Sep 17 00:00:00 2001 From: Matt Arsenault Date: Thu, 16 Jun 2016 16:33:41 +0000 Subject: [PATCH] LangRef: Note expectations when loading with extra alignment llvm-svn: 272914 --- llvm/docs/LangRef.rst | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index 086df648da47..42ee5bf72625 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -7019,7 +7019,12 @@ alignment for the target. It is the responsibility of the code emitter to ensure that the alignment information is correct. Overestimating the alignment results in undefined behavior. Underestimating the alignment may produce less efficient code. An alignment of 1 is always safe. The -maximum possible alignment is ``1 << 29``. +maximum possible alignment is ``1 << 29``. An alignment value higher +than the size of the loaded type implies memory up to the alignment +value bytes can be safely loaded without trapping in the default +address space. Access of the high bytes can interfere with debugging +tools, so should not be accessed if the function has the +``sanitize_thread`` or ``sanitize_address`` attributes. The optional ``!nontemporal`` metadata must reference a single metadata name ```` corresponding to a metadata node with one @@ -7144,7 +7149,14 @@ alignment for the target. It is the responsibility of the code emitter to ensure that the alignment information is correct. Overestimating the alignment results in undefined behavior. Underestimating the alignment may produce less efficient code. An alignment of 1 is always -safe. The maximum possible alignment is ``1 << 29``. +safe. The maximum possible alignment is ``1 << 29``. An alignment +value higher than the size of the stored type implies memory up to the +alignment value bytes can be stored to without trapping in the default +address space. Storing to the higher bytes however may result in data +races if another thread can access the same address. Introducing a +data race is not allowed. Storing to the extra bytes is not allowed +even in situations where a data race is known to not exist if the +function has the ``sanitize_address`` attribute. The optional ``!nontemporal`` metadata must reference a single metadata name ```` corresponding to a metadata node with one ``i32`` entry of