[ARM] Merging 64-bit divmod lib calls into one

When div+rem calls on the same arguments are found, the ARM back-end merges the
two calls into one __aeabi_divmod call for up to 32-bits values. However,
for 64-bit values, which also have a lib call (__aeabi_ldivmod), it wasn't
merging the calls, and thus calling ldivmod twice and spilling the temporary
results, which generated pretty bad code.

This patch legalises 64-bit lib calls for divmod, so that now all the spilling
and the second call are gone. It also relaxes the DivRem combiner a bit on the
legal type check, since it was already checking for isLegalOrCustom on every
value, so the extra check for isTypeLegal was redundant.

Second attempt, creating TLI.isOperationCustom like isOperationExpand, to make
sure we only emit valid types or the ones that were explicitly marked as custom.
Now, passing check-all and test-suite on x86, ARM and AArch64.

This patch fixes PR17193 (and a long time FIXME in the tests).

llvm-svn: 262738

1 files changed, 8 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 76187e29116..dfae183723f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2155,14 +2155,18 @@ SDValue DAGCombiner::useDivRem(SDNode *Node) {
   if (Node->use_empty())
     return SDValue(); // This is a dead node, leave it alone.
 
+  unsigned Opcode = Node->getOpcode();
+  bool isSigned = (Opcode == ISD::SDIV) || (Opcode == ISD::SREM);
+  unsigned DivRemOpc = isSigned ? ISD::SDIVREM : ISD::UDIVREM;
+
+  // DivMod lib calls can still work on non-legal types if using lib-calls.
   EVT VT = Node->getValueType(0);
-  if (!TLI.isTypeLegal(VT))
+  if (VT.isVector() || !VT.isInteger())
     return SDValue();
 
-  unsigned Opcode = Node->getOpcode();
-  bool isSigned = (Opcode == ISD::SDIV) || (Opcode == ISD::SREM);
+  if (!TLI.isTypeLegal(VT) && !TLI.isOperationCustom(DivRemOpc, VT))
+    return SDValue();
 
-  unsigned DivRemOpc = isSigned ? ISD::SDIVREM : ISD::UDIVREM;
   // If DIVREM is going to get expanded into a libcall,
   // but there is no libcall available, then don't combine.
   if (!TLI.isOperationLegalOrCustom(DivRemOpc, VT) &&