The DAGCombiner was threading select over pairs of extending loads even

if the extension types were not the same.  The result was that if you
fed a select with sext and zext loads, as in the testcase, then it
would get turned into a zext (or sext) of the select, which is wrong
in the cases when it should have been an sext (resp. zext).  Reported
and diagnosed by Sebastien Deldon.

llvm-svn: 119728

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1a0f503378d..53b449309c7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6658,6 +6658,11 @@ bool DAGCombiner::SimplifySelectOps(SDNode *TheSelect, SDValue LHS,
         LLD->isVolatile() || RLD->isVolatile() ||
         // If this is an EXTLOAD, the VT's must match.
         LLD->getMemoryVT() != RLD->getMemoryVT() ||
+        // If this is an EXTLOAD, the kind of extension must match.
+        (LLD->getExtensionType() != RLD->getExtensionType() &&
+         // The only exception is if one of the extensions is anyext.
+         LLD->getExtensionType() != ISD::EXTLOAD &&
+         RLD->getExtensionType() != ISD::EXTLOAD) ||
         // FIXME: this discards src value information.  This is
         // over-conservative. It would be beneficial to be able to remember
         // both potential memory locations.  Since we are discarding