Implement new way of expanding extloads.

Now that the source and destination types can be specified,
allow doing an expansion that doesn't use an EXTLOAD of the
result type. Try to do a legal extload to an intermediate type
and extend that if possible.

This generalizes the special case custom lowering of extloads
R600 has been using to work around this problem.

This also happens to fix a bug that would incorrectly use more
aligned loads than should be used.

llvm-svn: 225925

2 files changed, 19 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index ce8f96b7605..e5473e35cae 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -1090,22 +1090,25 @@ void SelectionDAGLegalize::LegalizeLoadOps(SDNode *Node) {
       break;
     }
     case TargetLowering::Expand:
-      if (!TLI.isLoadExtLegal(ISD::EXTLOAD, Node->getValueType(0),
-                              SrcVT) && TLI.isTypeLegal(SrcVT)) {
-        SDValue Load = DAG.getLoad(SrcVT, dl, Chain, Ptr, LD->getMemOperand());
-        unsigned ExtendOp;
-        switch (ExtType) {
-        case ISD::EXTLOAD:
-          ExtendOp = (SrcVT.isFloatingPoint() ?
-                      ISD::FP_EXTEND : ISD::ANY_EXTEND);
+      if (!TLI.isLoadExtLegal(ISD::EXTLOAD, Node->getValueType(0), SrcVT)) {
+        // If the source type is not legal, see if there is a legal extload to
+        // an intermediate type that we can then extend further.
+        EVT LoadVT = TLI.getRegisterType(SrcVT.getSimpleVT());
+        if (TLI.isTypeLegal(SrcVT) || // Same as SrcVT == LoadVT?
+            TLI.isLoadExtLegal(ExtType, LoadVT, SrcVT)) {
+          // If we are loading a legal type, this is a non-extload followed by a
+          // full extend.
+          ISD::LoadExtType MidExtType =
+              (LoadVT == SrcVT) ? ISD::NON_EXTLOAD : ExtType;
+
+          SDValue Load = DAG.getExtLoad(MidExtType, dl, LoadVT, Chain, Ptr,
+                                        SrcVT, LD->getMemOperand());
+          unsigned ExtendOp =
+              ISD::getExtForLoadExtType(SrcVT.isFloatingPoint(), ExtType);
+          Value = DAG.getNode(ExtendOp, dl, Node->getValueType(0), Load);
+          Chain = Load.getValue(1);
           break;
-        case ISD::SEXTLOAD: ExtendOp = ISD::SIGN_EXTEND; break;
-        case ISD::ZEXTLOAD: ExtendOp = ISD::ZERO_EXTEND; break;
-        default: llvm_unreachable("Unexpected extend load type!");
         }
-        Value = DAG.getNode(ExtendOp, dl, Node->getValueType(0), Load);
-        Chain = Load.getValue(1);
-        break;
       }
 
       assert(!SrcVT.isVector() &&
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index f271bd5122e..c819516eca0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -234,10 +234,10 @@ bool ISD::allOperandsUndef(const SDNode *N) {
   return true;
 }
 
-ISD::NodeType ISD::getExtForLoadExtType(ISD::LoadExtType ExtType) {
+ISD::NodeType ISD::getExtForLoadExtType(bool IsFP, ISD::LoadExtType ExtType) {
   switch (ExtType) {
   case ISD::EXTLOAD:
-    return ISD::ANY_EXTEND;
+    return IsFP ? ISD::FP_EXTEND : ISD::ANY_EXTEND;
   case ISD::SEXTLOAD:
     return ISD::SIGN_EXTEND;
   case ISD::ZEXTLOAD: