[AVR] Expand 16-bit rotations during the legalization stage

In r356860, the legalization logic for BSWAP was modified to ISD::ROTL,
rather than the old ISD::{SHL, SRL, OR} nodes.

This works fine on AVR for 8-bit rotations, but 16-bit rotations are
currently unimplemented - they always trigger an assertion error in the
AVRExpandPseudoInsts pass ("RORW unimplemented").

This patch instructions the legalizer to expand 16-bit rotations into
the previous SHL, SRL, OR pattern it did previously.

This fixes the 'issue-cannot-select-bswap.ll' test. Interestingly, this
test failure seems flaky - it passes successfully on the avr-build-01
buildbot, but fails locally on my Arch Linux install.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@362773 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AVR/AVRISelLowering.cpp b/lib/Target/AVR/AVRISelLowering.cpp
index 3103c20f0c2625122df3cd9d6cbc2fa4582f38f0..f6e1ba8d1b3686a9857395a4d77db0234b85a78f 100644 (file)
--- a/lib/Target/AVR/AVRISelLowering.cpp
+++ b/lib/Target/AVR/AVRISelLowering.cpp
@@ -89,9 +89,9 @@ AVRTargetLowering::AVRTargetLowering(const AVRTargetMachine &TM,
   setOperationAction(ISD::SRL_PARTS, MVT::i16, Expand);
 
   setOperationAction(ISD::ROTL, MVT::i8, Custom);
-  setOperationAction(ISD::ROTL, MVT::i16, Custom);
+  setOperationAction(ISD::ROTL, MVT::i16, Expand);
   setOperationAction(ISD::ROTR, MVT::i8, Custom);
-  setOperationAction(ISD::ROTR, MVT::i16, Custom);
+  setOperationAction(ISD::ROTR, MVT::i16, Expand);
 
   setOperationAction(ISD::BR_CC, MVT::i8, Custom);
   setOperationAction(ISD::BR_CC, MVT::i16, Custom);