R600: Move CONST_ADDRESS folding into AMDGPUDAGToDAGISel::Select()

This increases the number of opportunites we have for folding.  With the
previous implementation we were unable to fold into any instructions
other than the first when multiple instructions were selected from a
single SDNode.

Reviewed-by: Vincent Lejeune <vljn at ovi.com>
llvm-svn: 186919

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Target/R600/R600ISelLowering.cpp b/llvm/lib/Target/R600/R600ISelLowering.cpp
index dd613d56a60..a2bc2c3a9fa 100644
--- a/llvm/lib/Target/R600/R600ISelLowering.cpp
+++ b/llvm/lib/Target/R600/R600ISelLowering.cpp
@@ -1154,6 +1154,30 @@ SDValue R600TargetLowering::LowerLOAD(SDValue Op, SelectionDAG &DAG) const
     return DAG.getMergeValues(MergedValues, 2, DL);
   }
 
+  // For most operations returning SDValue() will result int he node being
+  // expanded by the DAG Legalizer.  This is not the case for ISD::LOAD, so
+  // we need to manually expand loads that may be legal in some address spaces
+  // and illegal in others.  SEXT loads from CONSTANT_BUFFER_0 are supported
+  // for compute shaders, since the data is sign extended when it is uploaded
+  // to the buffer.  Howerver SEXT loads from other addresspaces are not
+  // supported, so we need to expand them here.
+  if (LoadNode->getExtensionType() == ISD::SEXTLOAD) {
+    EVT MemVT = LoadNode->getMemoryVT();
+    assert(!MemVT.isVector() && (MemVT == MVT::i16 || MemVT == MVT::i8));
+    SDValue ShiftAmount =
+          DAG.getConstant(VT.getSizeInBits() - MemVT.getSizeInBits(), MVT::i32);
+    SDValue NewLoad = DAG.getExtLoad(ISD::EXTLOAD, DL, VT, Chain, Ptr,
+                                  LoadNode->getPointerInfo(), MemVT,
+                                  LoadNode->isVolatile(),
+                                  LoadNode->isNonTemporal(),
+                                  LoadNode->getAlignment());
+    SDValue Shl = DAG.getNode(ISD::SHL, DL, VT, NewLoad, ShiftAmount);
+    SDValue Sra = DAG.getNode(ISD::SRA, DL, VT, Shl, ShiftAmount);
+
+    SDValue MergedValues[2] = { Sra, Chain };
+    return DAG.getMergeValues(MergedValues, 2, DL);
+  }
+
   if (LoadNode->getAddressSpace() != AMDGPUAS::PRIVATE_ADDRESS) {
     return SDValue();
   }