From 4283499dcd76355d1c8ee4b28883635e967b7c81 Mon Sep 17 00:00:00 2001 From: Michael Gottesman Date: Sun, 3 Feb 2013 09:57:15 +0000 Subject: Added clarification paragraph to LangRef's documentation of GlobalVariable about LLVM's assumptions vis-a-vis Global Variable initial values and Global Variable initializers. This is in preparation for adding the new keyword externally_initialized. Specifically, the patch explains how LLVM optimizes global initializers by assumign that global variables defined within the module are not modified from their initial values before the start of the global initializer. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174269 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/LangRef.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/docs/LangRef.rst b/docs/LangRef.rst index d3bfddd..c9f37bd 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -501,6 +501,13 @@ is zero. The address space qualifier must precede any other attributes. LLVM allows an explicit section to be specified for globals. If the target supports it, it will emit globals to the section specified. +By default, LLVM optimizes global initializers by assuming that global +variables defined within the module are not modified from their +initial values before the start of the global initializer. This is +true even for variables potentially accessible from outside the +module, including those with external linkage or appearing in +``@llvm.used``. + An explicit alignment may be specified for a global, which must be a power of 2. If not present, or if the alignment is set to zero, the alignment of the global is set by the target to whatever it feels -- cgit v1.1