Merging r323857:

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r323857 | rogfer01 | 2018-01-31 10:23:43 +0100 (Wed, 31 Jan 2018) | 19 lines

[ARM] Allow the scheduler to clone a node with glue to avoid a copy CPSR ↔ GPR.

In Thumb 1, with the new ADDCARRY / SUBCARRY the scheduler may need to do
copies CPSR ↔ GPR but not all Thumb1 targets implement them.

The schedule can attempt, before attempting a copy, to clone the instructions
but it does not currently do that for nodes with input glue. In this patch we
introduce a target-hook to let the hook decide if a glued machinenode is still
eligible for copying. In this case these are ARM::tADCS and ARM::tSBCS .

As a follow-up of this change we should actually implement the copies for the
Thumb1 targets that do implement them and restrict the hook to the targets that
can't really do such copy as these clones are not ideal.

This change fixes PR35836.

Differential Revision: https://reviews.llvm.org/D42051


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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@324082 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 4 deletions

diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index 49f304c8cc8..82337d43c5c 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -1117,22 +1117,34 @@ SUnit *ScheduleDAGRRList::CopyAndMoveSuccessors(SUnit *SU) {
   if (!N)
     return nullptr;
 
-  if (SU->getNode()->getGluedNode())
+  DEBUG(dbgs() << "Considering duplicating the SU\n");
+  DEBUG(SU->dump(this));
+
+  if (N->getGluedNode() &&
+      !TII->canCopyGluedNodeDuringSchedule(N)) {
+    DEBUG(dbgs()
+        << "Giving up because it has incoming glue and the target does not "
+           "want to copy it\n");
     return nullptr;
+  }
 
   SUnit *NewSU;
   bool TryUnfold = false;
   for (unsigned i = 0, e = N->getNumValues(); i != e; ++i) {
     MVT VT = N->getSimpleValueType(i);
-    if (VT == MVT::Glue)
+    if (VT == MVT::Glue) {
+      DEBUG(dbgs() << "Giving up because it has outgoing glue\n");
       return nullptr;
-    else if (VT == MVT::Other)
+    } else if (VT == MVT::Other)
       TryUnfold = true;
   }
   for (const SDValue &Op : N->op_values()) {
     MVT VT = Op.getNode()->getSimpleValueType(Op.getResNo());
-    if (VT == MVT::Glue)
+    if (VT == MVT::Glue && !TII->canCopyGluedNodeDuringSchedule(N)) {
+      DEBUG(dbgs() << "Giving up because it one of the operands is glue and "
+                      "the target does not want to copy it\n");
       return nullptr;
+    }
   }
 
   // If possible unfold instruction.