[PATCH] D53229: [LegalizeTypes] Teach PromoteIntRes_BITCAST to better handle a bitcast with vector output type and a vector input type that needs to be widened

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: efriedma, RKSimon.

Previously if we had a bitcast vector output type that needs promotion and a vector input type that needs widening we would just do a stack store and load to handle the conversion. We can do a little better if we can widen the bitcast to a legal vector type the same size as the widened input type. Then we can do the bitcast between this widened type and the widened input type. Afterwards we can extract_subvector back to the original output and any_extend that. Type legalization will then circle back and handle promotion of the extract_subvector and the any_extend will just be removed. This will avoid going through the stack and allows us to remove a custom version of this legalization from X86.


https://reviews.llvm.org/D53229

Files:
  lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
  lib/Target/X86/X86ISelLowering.cpp


Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -26296,22 +26296,16 @@
       return;
     }
 
-    if ((SrcVT != MVT::f64 && SrcVT != MVT::v2f32) ||
+    if (SrcVT != MVT::f64 ||
         (DstVT != MVT::v2i32 && DstVT != MVT::v4i16 && DstVT != MVT::v8i8) ||
         getTypeAction(*DAG.getContext(), DstVT) == TypeWidenVector)
       return;
 
     unsigned NumElts = DstVT.getVectorNumElements();
     EVT SVT = DstVT.getVectorElementType();
     EVT WiderVT = EVT::getVectorVT(*DAG.getContext(), SVT, NumElts * 2);
     SDValue Res;
-    if (SrcVT == MVT::f64)
-      Res = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl,
-                             MVT::v2f64, N->getOperand(0));
-    else
-      Res = DAG.getNode(ISD::CONCAT_VECTORS, dl, MVT::v4f32, N->getOperand(0),
-                        DAG.getUNDEF(MVT::v2f32));
-
+    Res = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, MVT::v2f64, N->getOperand(0));
     Res = DAG.getBitcast(WiderVT, Res);
     Res = DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, DstVT, Res,
                       DAG.getIntPtrConstant(0, dl));
Index: lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -305,6 +305,26 @@
     // make us bitcast between two vectors which are legalized in different ways.
     if (NOutVT.bitsEq(NInVT) && !NOutVT.isVector())
       return DAG.getNode(ISD::BITCAST, dl, NOutVT, GetWidenedVector(InOp));
+    // If the output type is also a vector and widening it to the same size
+    // as the widened input type would be a legal type, we can widen the bitcast
+    // and handle the promotion after.
+    if (NOutVT.isVector()) {
+      unsigned WidenInSize = NInVT.getSizeInBits();
+      unsigned OutSize = OutVT.getSizeInBits();
+      if (WidenInSize % OutSize == 0) {
+        unsigned Scale = WidenInSize / OutSize;
+        EVT WideOutVT = EVT::getVectorVT(*DAG.getContext(),
+                                         OutVT.getVectorElementType(),
+                                         OutVT.getVectorNumElements() * Scale);
+        if (isTypeLegal(WideOutVT)) {
+          InOp = DAG.getBitcast(WideOutVT, GetWidenedVector(InOp));
+          MVT IdxTy = TLI.getVectorIdxTy(DAG.getDataLayout());
+          InOp = DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, OutVT, InOp,
+                             DAG.getConstant(0, dl, IdxTy));
+          return DAG.getNode(ISD::ANY_EXTEND, dl, NOutVT, InOp);
+        }
+      }
+    }
   }
 
   return DAG.getNode(ISD::ANY_EXTEND, dl, NOutVT,


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