[PATCH] D79421: [CodeGen] Fix FoldConstantVectorArithmetic for scalable vectors

[David Sherwood via Phabricator via llvm-commits]

david-arm updated this revision to Diff 264176.
david-arm edited the summary of this revision.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D79421/new/

https://reviews.llvm.org/D79421

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp


Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4915,8 +4915,14 @@
     if (GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(N2))
       return FoldSymbolOffset(Opcode, VT, GA, N1);
 
-  // For vectors, extract each constant element and fold them individually.
-  // Either input may be an undef value.
+  // TODO: All the folds below are performed lane-by-lane and assume a fixed
+  // vector width, however we should be able to do constant folds involving
+  // splat vector nodes too.
+  if (VT.isScalableVector())
+    return SDValue();
+
+  // For fixed width vectors, extract each constant element and fold them
+  // individually. Either input may be an undef value.
   auto *BV1 = dyn_cast<BuildVectorSDNode>(N1);
   if (!BV1 && !N1->isUndef())
     return SDValue();
@@ -4992,6 +4998,13 @@
   if (!VT.isVector())
     return SDValue();
 
+  // TODO: All the folds below are performed lane-by-lane and assume a fixed
+  // vector width, however we should be able to do constant folds involving
+  // splat vector nodes too.
+  if (VT.isScalableVector())
+    return SDValue();
+
+  // From this point onwards all vectors are assumed to be fixed width.
   unsigned NumElts = VT.getVectorNumElements();
 
   auto IsScalarOrSameVectorSize = [&](const SDValue &Op) {


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