Lower mem-ops to unaligned i32/i16 load/stores on ARM where supported.

Add support for trimming constants to GetDemandedBits. This fixes some funky
constant generation that occurs when stores are expanded for targets that don't
support unaligned stores natively.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144102 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 17 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index e67016ca0c..8b28ea997f 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4564,6 +4564,16 @@ SDValue DAGCombiner::visitANY_EXTEND(SDNode *N) {
 SDValue DAGCombiner::GetDemandedBits(SDValue V, const APInt &Mask) {
   switch (V.getOpcode()) {
   default: break;
+  case ISD::Constant: {
+    const ConstantSDNode *CV = cast<ConstantSDNode>(V.getNode());
+    assert(CV != 0 && "Const value should be ConstSDNode.");
+    const APInt &CVal = CV->getAPIntValue();
+    APInt NewVal = CVal & Mask;
+    if (NewVal != CVal) {
+      return DAG.getConstant(NewVal, V.getValueType());
+    }
+    break;
+  }
   case ISD::OR:
   case ISD::XOR:
     // If the LHS or RHS don't contribute bits to the or, drop them.
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 84a34d587b..c51e7ae535 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -8171,6 +8171,13 @@ EVT ARMTargetLowering::getOptimalMemOpType(uint64_t Size,
     }
   }
 
+  // Lowering to i32/i16 if the size permits.
+  if (Size >= 4) {
+    return MVT::i32;
+  } else if (Size >= 2) {
+    return MVT::i16;
+  }
+
   // Let the target-independent logic figure it out.
   return MVT::Other;
 }