X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FFAQ.rst;h=8db94c6250c199505293c5ef91f789feb730ab8f;hb=daf061cf05d9ea2682c660f8208c40776f926cde;hp=67e8d0b27b26ee4ba991b638b6bd24c6643eb639;hpb=527036d5ff4bcb1afe6e85cfab9a3d85dcc5db7b;p=oota-llvm.git

diff --git a/docs/FAQ.rst b/docs/FAQ.rst
index 67e8d0b27b2..8db94c6250c 100644
--- a/docs/FAQ.rst
+++ b/docs/FAQ.rst
@@ -1,5 +1,3 @@
-.. _faq:
-
 ================================
 Frequently Asked Questions (FAQ)
 ================================
@@ -53,6 +51,29 @@ Some porting problems may exist in the following areas:
   like the Bourne Shell and sed.  Porting to systems without these tools
   (MacOS 9, Plan 9) will require more effort.
 
+What API do I use to store a value to one of the virtual registers in LLVM IR's SSA representation?
+---------------------------------------------------------------------------------------------------
+
+In short: you can't. It's actually kind of a silly question once you grok
+what's going on. Basically, in code like:
+
+.. code-block:: llvm
+
+    %result = add i32 %foo, %bar
+
+, ``%result`` is just a name given to the ``Value`` of the ``add``
+instruction. In other words, ``%result`` *is* the add instruction. The
+"assignment" doesn't explicitly "store" anything to any "virtual register";
+the "``=``" is more like the mathematical sense of equality.
+
+Longer explanation: In order to generate a textual representation of the
+IR, some kind of name has to be given to each instruction so that other
+instructions can textually reference it. However, the isomorphic in-memory
+representation that you manipulate from C++ has no such restriction since
+instructions can simply keep pointers to any other ``Value``'s that they
+reference. In fact, the names of dummy numbered temporaries like ``%1`` are
+not explicitly represented in the in-memory representation at all (see
+``Value::getName()``).
 
 Build Problems
 ==============
@@ -163,14 +184,6 @@ This is `a bug in GCC <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13392>`_,
 and affects projects other than LLVM.  Try upgrading or downgrading your GCC.
 
 
-Compiling LLVM with GCC succeeds, but the resulting tools do not work, what can be wrong?
------------------------------------------------------------------------------------------
-Several versions of GCC have shown a weakness in miscompiling the LLVM
-codebase.  Please consult your compiler version (``gcc --version``) to find
-out whether it is `broken <GettingStarted.html#brokengcc>`_.  If so, your only
-option is to upgrade GCC to a known good version.
-
-
 After Subversion update, rebuilding gives the error "No rule to make target".
 -----------------------------------------------------------------------------
 If the error is of the form: