<div dir="ltr"><div>Not sure ComputeKnownBits etc. really helps with that sort of transform? I mean, fundamentally the basic transform we're talking about here is "x ^ 1 ^ 2" <-> "x ^ 3", which is basically reassociation.<br><br></div>-Eli<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jul 13, 2016 at 1:01 PM, Sanjay Patel <span dir="ltr"><<a href="mailto:spatel@rotateright.com" target="_blank">spatel@rotateright.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Sure. The general theme is that casts of all flavors interfere with all optimizations. Is the solution to use ValueTracking (computeKnownBits, etc) more liberally than pattern matching?<br></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jul 13, 2016 at 1:23 PM, Eli Friedman <span dir="ltr"><<a href="mailto:eli.friedman@gmail.com" target="_blank">eli.friedman@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>On Wed, Jul 13, 2016 at 11:40 AM, Sanjay Patel via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br></div></div><div class="gmail_extra"><div class="gmail_quote"><div><div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: spatel<br>
Date: Wed Jul 13 13:40:38 2016<br>
New Revision: 275297<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=275297&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=275297&view=rev</a><br>
Log:<br>
add test for zexty xor sandwich<br>
<br>
Modified:<br>
    llvm/trunk/test/Transforms/InstCombine/xor.ll<br>
<br>
Modified: llvm/trunk/test/Transforms/InstCombine/xor.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/xor.ll?rev=275297&r1=275296&r2=275297&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/xor.ll?rev=275297&r1=275296&r2=275297&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/test/Transforms/InstCombine/xor.ll (original)<br>
+++ llvm/trunk/test/Transforms/InstCombine/xor.ll Wed Jul 13 13:40:38 2016<br>
@@ -242,6 +242,20 @@ define i32 @test22(i1 %X) {<br>
   ret i32 %Q<br>
 }<br>
<br>
+; Look through a zext between xors.<br>
+<br>
+define i32 @fold_zext_xor_sandwich(i1 %X) {<br>
+; CHECK-LABEL: @fold_zext_xor_sandwich(<br>
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i1 %X to i32<br>
+; CHECK-NEXT:    [[Q:%.*]] = xor i32 [[TMP1]], 3<br>
+; CHECK-NEXT:    ret i32 [[Q]]<br>
+;<br>
+  %Y = xor i1 %X, true<br>
+  %Z = zext i1 %Y to i32<br>
+  %Q = xor i32 %Z, 2<br>
+  ret i32 %Q<br>
+}<br><br></blockquote><div><br></div></div></div><div>You might want to write a similar testcase replacing the "xor" with an "or".<span><font color="#888888"><br></font></span></div><span><font color="#888888"><div><br></div><div>-Eli<br></div></font></span></div></div></div>
</blockquote></div><br></div>
</div></div></blockquote></div><br></div>