[mips] Fix multiprecision arithmetic.

For multiprecision arithmetic on MIPS, rather than using ISD::ADDE / ISD::ADDC,
get SelectionDAG to break down the operation into ISD::ADDs and ISD::SETCCs.

For MIPS, only the DSP ASE has a carry flag, so in the general case it is not
useful to directly support ISD::{ADDE, ADDC, SUBE, SUBC} nodes.

Also improve the generation code in such cases for targets with
TargetLoweringBase::ZeroOrOneBooleanContent by directly using the result of the
comparison node rather than using it in selects. Similarly for ISD::SUBE /
ISD::SUBC.

Address optimization breakage by moving the generation of MIPS specific integer
multiply-accumulate nodes to before legalization.

This revolves PR32713 and PR33424.

Thanks to Simonas Kazlauskas and Pirama Arumuga Nainar for reporting the issue!

Reviewers: slthakur

Differential Revision: https://reviews.llvm.org/D33494

llvm-svn: 305389

1 files changed, 17 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 0d5e07ded25..a3ba52a148e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -1828,10 +1828,11 @@ void DAGTypeLegalizer::ExpandIntRes_ADDSUB(SDNode *N,
     TLI.isOperationLegalOrCustom(N->getOpcode() == ISD::ADD ?
                                    ISD::UADDO : ISD::USUBO,
                                  TLI.getTypeToExpandTo(*DAG.getContext(), NVT));
+  TargetLoweringBase::BooleanContent BoolType = TLI.getBooleanContents(NVT);
+
   if (hasOVF) {
     EVT OvfVT = getSetCCResultType(NVT);
     SDVTList VTList = DAG.getVTList(NVT, OvfVT);
-    TargetLoweringBase::BooleanContent BoolType = TLI.getBooleanContents(NVT);
     int RevOpc;
     if (N->getOpcode() == ISD::ADD) {
       RevOpc = ISD::SUB;
@@ -1864,6 +1865,13 @@ void DAGTypeLegalizer::ExpandIntRes_ADDSUB(SDNode *N,
     Hi = DAG.getNode(ISD::ADD, dl, NVT, makeArrayRef(HiOps, 2));
     SDValue Cmp1 = DAG.getSetCC(dl, getSetCCResultType(NVT), Lo, LoOps[0],
                                 ISD::SETULT);
+
+    if (BoolType == TargetLoweringBase::ZeroOrOneBooleanContent) {
+      SDValue Carry = DAG.getZExtOrTrunc(Cmp1, dl, NVT);
+      Hi = DAG.getNode(ISD::ADD, dl, NVT, Hi, Carry);
+      return;
+    }
+
     SDValue Carry1 = DAG.getSelect(dl, NVT, Cmp1,
                                    DAG.getConstant(1, dl, NVT),
                                    DAG.getConstant(0, dl, NVT));
@@ -1878,9 +1886,14 @@ void DAGTypeLegalizer::ExpandIntRes_ADDSUB(SDNode *N,
     SDValue Cmp =
       DAG.getSetCC(dl, getSetCCResultType(LoOps[0].getValueType()),
                    LoOps[0], LoOps[1], ISD::SETULT);
-    SDValue Borrow = DAG.getSelect(dl, NVT, Cmp,
-                                   DAG.getConstant(1, dl, NVT),
-                                   DAG.getConstant(0, dl, NVT));
+
+    SDValue Borrow;
+    if (BoolType == TargetLoweringBase::ZeroOrOneBooleanContent)
+      Borrow = DAG.getZExtOrTrunc(Cmp, dl, NVT);
+    else
+      Borrow = DAG.getSelect(dl, NVT, Cmp, DAG.getConstant(1, dl, NVT),
+                             DAG.getConstant(0, dl, NVT));
+
     Hi = DAG.getNode(ISD::SUB, dl, NVT, Hi, Borrow);
   }
 }