<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 23, 2015 at 11:00 PM, Justin Bogner <span dir="ltr"><<a href="mailto:mail@justinbogner.com" target="_blank">mail@justinbogner.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Author: bogner<br>
Date: Wed Jun 24 01:00:53 2015<br>
New Revision: 240521<br>
<br>
URL: <a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D240521-26view-3Drev&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=0n5-e-aWPrIa9UJN57Uh1sYz4e9Z83u53a6zWOwlPW0&s=uYPJVY_dIqu3hx_KTTFIfSb1AKfNfNFRXm_-gOVA_uo&e=" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=240521&view=rev</a><br>
Log:<br>
Hexagon: Avoid left shifting negative values (it's UB)<br>
<br>
Found by ubsan.<br>
<br>
Modified:<br>
    llvm/trunk/lib/Target/Hexagon/MCTargetDesc/HexagonShuffler.h<br>
<br>
Modified: llvm/trunk/lib/Target/Hexagon/MCTargetDesc/HexagonShuffler.h<br>
URL: <a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_llvm_trunk_lib_Target_Hexagon_MCTargetDesc_HexagonShuffler.h-3Frev-3D240521-26r1-3D240520-26r2-3D240521-26view-3Ddiff&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=0n5-e-aWPrIa9UJN57Uh1sYz4e9Z83u53a6zWOwlPW0&s=kAdzozyiKh4-UXhqDlUcNV0ng5d4FFP-yEGU_s3hlfQ&e=" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/MCTargetDesc/HexagonShuffler.h?rev=240521&r1=240520&r2=240521&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Target/Hexagon/MCTargetDesc/HexagonShuffler.h (original)<br>
+++ llvm/trunk/lib/Target/Hexagon/MCTargetDesc/HexagonShuffler.h Wed Jun 24 01:00:53 2015<br>
@@ -34,7 +34,7 @@ public:<br>
   HexagonResource(unsigned s) { setUnits(s); };<br>
<br>
   void setUnits(unsigned s) {<br>
-    Slots = s & ~(-1 << HEXAGON_PACKET_SIZE);<br>
+    Slots = s & ~(~0U << HEXAGON_PACKET_SIZE);<br></blockquote><div><br></div><div>ISTM that this is equivalent to `s & ((1 << HEXAGON_PACKET_SIZE) - 1)`.  Personally, I find that this version is more obvious while still avoiding UB.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
     setWeight(s);<br>
   };<br>
   unsigned setWeight(unsigned s);<br>
<br>
<br>
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</blockquote></div><br></div></div>