[llvm-commits] [llvm] r102381 - /llvm/trunk/docs/LangRef.html

[Dan Gohman]

Author: djg
Date: Mon Apr 26 15:54:53 2010
New Revision: 102381

URL: http://llvm.org/viewvc/llvm-project?rev=102381&view=rev
Log:
Branching or switching on trap transfers imminent undefined behavior
onto control-dependent instructions.

Modified:
    llvm/trunk/docs/LangRef.html

Modified: llvm/trunk/docs/LangRef.html
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/LangRef.html?rev=102381&r1=102380&r2=102381&view=diff
==============================================================================
--- llvm/trunk/docs/LangRef.html (original)
+++ llvm/trunk/docs/LangRef.html Mon Apr 26 15:54:53 2010
@@ -2318,6 +2318,15 @@
    Any instruction with a trap operand which may have side effects emits
    those side effects as if it had an undef operand instead.</p>
 
+<p>If a <a href="#i_br"><tt>br</tt></a> or
+   <a href="#i_switch"><tt>switch</tt></a> instruction has a trap value
+   operand, all non-phi non-void instructions which control-depend on it
+   have trap as their result value. If any instruction which
+   control-depends on the <tt>br</tt> or <tt>switch</tt> invokes externally
+   visible side effects, the behavior of the program is undefined.</p>
+
+<!-- FIXME: What about exceptions thrown from control-dependent instrs? -->
+
 <p>For example, an <a href="#i_and"><tt>and</tt></a> of a trap value with
    zero still has a trap value result. Using that value as an index in a
    <a href="#i_getelementptr"><tt>getelementptr</tt></a> yields a trap