[DAGCombiner] Support {a|s}ext, {a|z|s}ext load nodes in load combine

Resubmit -r295314 with PowerPC and AMDGPU tests updated.

Support {a|s}ext, {a|z|s}ext load nodes as a part of load combine patters.

Reviewed By: filcab

Differential Revision: https://reviews.llvm.org/D29591

llvm-svn: 295336

1 files changed, 19 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index cb356c63c9b..25a6431ea75 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4446,6 +4446,8 @@ const Optional<ByteProvider> calculateByteProvider(SDValue Op, unsigned Index,
                : calculateByteProvider(Op->getOperand(0), Index - ByteShift,
                                        Depth + 1);
   }
+  case ISD::ANY_EXTEND:
+  case ISD::SIGN_EXTEND:
   case ISD::ZERO_EXTEND: {
     SDValue NarrowOp = Op->getOperand(0);
     unsigned NarrowBitWidth = NarrowOp.getScalarValueSizeInBits();
@@ -4453,22 +4455,32 @@ const Optional<ByteProvider> calculateByteProvider(SDValue Op, unsigned Index,
       return None;
     uint64_t NarrowByteWidth = NarrowBitWidth / 8;
 
-    return Index >= NarrowByteWidth
-               ? ByteProvider::getConstantZero()
-               : calculateByteProvider(NarrowOp, Index, Depth + 1);
+    if (Index >= NarrowByteWidth)
+      return Op.getOpcode() == ISD::ZERO_EXTEND
+                 ? Optional<ByteProvider>(ByteProvider::getConstantZero())
+                 : None;
+    else
+      return calculateByteProvider(NarrowOp, Index, Depth + 1);
   }
   case ISD::BSWAP:
     return calculateByteProvider(Op->getOperand(0), ByteWidth - Index - 1,
                                  Depth + 1);
   case ISD::LOAD: {
     auto L = cast<LoadSDNode>(Op.getNode());
+    if (L->isVolatile() || L->isIndexed())
+      return None;
 
-    // TODO: support ext loads
-    if (L->isVolatile() || L->isIndexed() ||
-        L->getExtensionType() != ISD::NON_EXTLOAD)
+    unsigned NarrowBitWidth = L->getMemoryVT().getSizeInBits();
+    if (NarrowBitWidth % 8 != 0)
       return None;
+    uint64_t NarrowByteWidth = NarrowBitWidth / 8;
 
-    return ByteProvider::getMemory(L, Index);
+    if (Index >= NarrowByteWidth)
+      return L->getExtensionType() == ISD::ZEXTLOAD
+                 ? Optional<ByteProvider>(ByteProvider::getConstantZero())
+                 : None;
+    else
+      return ByteProvider::getMemory(L, Index);
   }
   }
 
@@ -4548,7 +4560,6 @@ SDValue DAGCombiner::MatchLoadCombine(SDNode *N) {
 
     LoadSDNode *L = P->Load;
     assert(L->hasNUsesOfValue(1, 0) && !L->isVolatile() && !L->isIndexed() &&
-           (L->getExtensionType() == ISD::NON_EXTLOAD) &&
            "Must be enforced by calculateByteProvider");
     assert(L->getOffset().isUndef() && "Unindexed load must have undef offset");