enhance vmcore to know that udiv's can be exact, and add a trivial

instcombine xform to exercise this.

Nothing forms exact udivs yet though.  This is progress on PR8862

llvm-svn: 124992

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/docs/LangRef.html b/llvm/docs/LangRef.html
index da365ff808a..f7997495e04 100644
--- a/llvm/docs/LangRef.html
+++ b/llvm/docs/LangRef.html
@@ -3441,7 +3441,8 @@ Instruction</a> </div>
 
 <h5>Syntax:</h5>
 <pre>
-  &lt;result&gt; = udiv &lt;ty&gt; &lt;op1&gt;, &lt;op2&gt;   <i>; yields {ty}:result</i>
+  &lt;result&gt; = udiv &lt;ty&gt; &lt;op1&gt;, &lt;op2&gt;         <i>; yields {ty}:result</i>
+  &lt;result&gt; = udiv exact &lt;ty&gt; &lt;op1&gt;, &lt;op2&gt;   <i>; yields {ty}:result</i>
 </pre>
 
 <h5>Overview:</h5>
@@ -3460,6 +3461,11 @@ Instruction</a> </div>
 
 <p>Division by zero leads to undefined behavior.</p>
 
+<p>If the <tt>exact</tt> keyword is present, the result value of the
+   <tt>udiv</tt> is a <a href="#trapvalues">trap value</a> if %op1 is not a
+  multiple of %op2 (as such, "((a udiv exact b) mul b) == a").</p>
+
+
 <h5>Example:</h5>
 <pre>
   &lt;result&gt; = udiv i32 4, %var          <i>; yields {i32}:result = 4 / %var</i>