[RISCV] Remove sext_inreg+add/sub/mul/shl isel patterns.

[craig.topper]

Summary

Let the sext_inreg be selected to sext.w. Remove unneeded sext.w
during PostProcessISelDAG.

This gives opportunities for some other isel patterns to match
like the ADDIPair or matching mul with immediate to shXadd.

This becomes possible after D107658 started selecting W instructions
based on users. The sext.w will be considered a W user so isel
will often select a W instruction for the sext.w input and we can
just remove the sext.w. Otherwise we can combine the sext.w with
a ADD/SUB/MUL/SLLI to create a new W instruction in parallel
to the the original instruction.

[craig.topper]

Rebase

[craig.topper]

Rebase on new tests that have been added.
Factor the new post isel peephole into a helper function.

[luismarques]

LGTM.

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.h

 //===---- RISCVISelDAGToDAG.h - A dag to dag inst selector for RISCV ------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
public:
   void selectVLXSEG(SDNode *Node, bool IsMasked, bool IsOrdered);
   void selectVSSEG(SDNode *Node, bool IsMasked, bool IsStrided);
   void selectVSXSEG(SDNode *Node, bool IsMasked, bool IsOrdered);
 
 // Include the pieces autogenerated from the target description.
 #include "RISCVGenDAGISel.inc"
 
 private:
-  void doPeepholeLoadStoreADDI();
+  bool doPeepholeLoadStoreADDI(SDNode *Node);
 };
 
 namespace RISCV {
 struct VLSEGPseudo {
   uint16_t NF : 4;
   uint16_t Masked : 1;
   uint16_t Strided : 1;
   uint16_t FF : 1;

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

 //===-- RISCVISelDAGToDAG.cpp - A dag to dag inst selector for RISCV ------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
for (SelectionDAG::allnodes_iterator I = CurDAG->allnodes_begin(),
     // Now that we did that, the node is dead.  Increment the iterator to the
     // next node to process, then delete N.
     ++I;
     CurDAG->DeleteNode(N);
   }
 }
 
 void RISCVDAGToDAGISel::PostprocessISelDAG() {
-  doPeepholeLoadStoreADDI();
+  SelectionDAG::allnodes_iterator Position = CurDAG->allnodes_end();
+
+  bool MadeChange = false;
+  while (Position != CurDAG->allnodes_begin()) {
+    SDNode *N = &*--Position;
+    // Skip dead nodes and any non-machine opcodes.
+    if (N->use_empty() || !N->isMachineOpcode())
+      continue;
+
+    // Try to remove sext.w.
+    if (N->getMachineOpcode() == RISCV::ADDIW &&
+        isNullConstant(N->getOperand(1))) {
+      SDValue N0 = N->getOperand(0);
+      if (!N0.isMachineOpcode())
+        continue;
+
+      switch (N0.getMachineOpcode()) {
+      default:
+        break;
+      case RISCV::ADD:
+      case RISCV::ADDI:
+      case RISCV::SUB:
+      case RISCV::MUL:
+      case RISCV::SLLI: {
+        // Convert sext.w+add/sub/mul to their W instructions. This will create
+        // a new independent instruction. This improves latency.
+        unsigned Opc;
+        switch (N0.getMachineOpcode()) {
+        default:
+          llvm_unreachable("Unexpected opcode!");
+        case RISCV::ADD:  Opc = RISCV::ADDW;  break;
+        case RISCV::ADDI: Opc = RISCV::ADDIW; break;
+        case RISCV::SUB:  Opc = RISCV::SUBW;  break;
+        case RISCV::MUL:  Opc = RISCV::MULW;  break;
+        case RISCV::SLLI: Opc = RISCV::SLLIW; break;
+        }
+
+        SDValue N00 = N0.getOperand(0);
+        SDValue N01 = N0.getOperand(1);
+
+        // Shift amount needs to be uimm5.
+        if (N0.getMachineOpcode() == RISCV::SLLI &&
+            !isUInt<5>(cast<ConstantSDNode>(N01)->getSExtValue()))
+          break;
+
+        SDNode *Result =
+            CurDAG->getMachineNode(Opc, SDLoc(N), N->getValueType(0),
+                                   N00, N01);
+        ReplaceUses(N, Result);
+        MadeChange = true;
+        continue;
+      }
+      case RISCV::ADDW:
+      case RISCV::ADDIW:
+      case RISCV::SUBW:
+      case RISCV::MULW:
+      case RISCV::SLLIW:
+        // Result is already sign extended just remove the sext.w.
+        // NOTE: We only handle the nodes that are selected with hasAllWUsers.
+        ReplaceUses(N, N0.getNode());
+        MadeChange = true;
+        continue;
+      }
+
+      continue;
+    }
+
+    MadeChange |= doPeepholeLoadStoreADDI(N);
+  }
+
+  if (MadeChange)
+    CurDAG->RemoveDeadNodes();
 }
 
 static SDNode *selectImm(SelectionDAG *CurDAG, const SDLoc &DL, int64_t Imm,
                          const RISCVSubtarget &Subtarget) {
   MVT XLenVT = Subtarget.getXLenVT();
   RISCVMatInt::InstSeq Seq =
       RISCVMatInt::generateInstSeq(Imm, Subtarget.getFeatureBits());
 
bool RISCVDAGToDAGISel::selectRVVSimm5(SDValue N, unsigned Width,
 
   return false;
 }
 
 // Merge an ADDI into the offset of a load/store instruction where possible.
 // (load (addi base, off1), off2) -> (load base, off1+off2)
 // (store val, (addi base, off1), off2) -> (store val, base, off1+off2)
 // This is possible when off1+off2 fits a 12-bit immediate.
-void RISCVDAGToDAGISel::doPeepholeLoadStoreADDI() {
-  SelectionDAG::allnodes_iterator Position(CurDAG->getRoot().getNode());
-  ++Position;
-
-  while (Position != CurDAG->allnodes_begin()) {
-    SDNode *N = &*--Position;
-    // Skip dead nodes and any non-machine opcodes.
-    if (N->use_empty() || !N->isMachineOpcode())
-      continue;
-
-    int OffsetOpIdx;
-    int BaseOpIdx;
+bool RISCVDAGToDAGISel::doPeepholeLoadStoreADDI(SDNode *N) {
 
-    // Only attempt this optimisation for I-type loads and S-type stores.
-    switch (N->getMachineOpcode()) {
-    default:
-      continue;
-    case RISCV::LB:
-    case RISCV::LH:
-    case RISCV::LW:
-    case RISCV::LBU:
-    case RISCV::LHU:
-    case RISCV::LWU:
-    case RISCV::LD:
-    case RISCV::FLH:
-    case RISCV::FLW:
-    case RISCV::FLD:
-      BaseOpIdx = 0;
-      OffsetOpIdx = 1;
-      break;
-    case RISCV::SB:
-    case RISCV::SH:
-    case RISCV::SW:
-    case RISCV::SD:
-    case RISCV::FSH:
-    case RISCV::FSW:
-    case RISCV::FSD:
-      BaseOpIdx = 1;
-      OffsetOpIdx = 2;
-      break;
-    }
+    return false;
 
-    if (!isa<ConstantSDNode>(N->getOperand(OffsetOpIdx)))
-      continue;
+    return false;
 
-    SDValue Base = N->getOperand(BaseOpIdx);
 
-    // If the base is an ADDI, we can merge it in to the load/store.
-    if (!Base.isMachineOpcode() || Base.getMachineOpcode() != RISCV::ADDI)
-      continue;
+    return false;
 
-    SDValue ImmOperand = Base.getOperand(1);
-    uint64_t Offset2 = N->getConstantOperandVal(OffsetOpIdx);
 
-    if (auto *Const = dyn_cast<ConstantSDNode>(ImmOperand)) {
-      int64_t Offset1 = Const->getSExtValue();
-      int64_t CombinedOffset = Offset1 + Offset2;
-      if (!isInt<12>(CombinedOffset))
-        continue;
-      ImmOperand = CurDAG->getTargetConstant(CombinedOffset, SDLoc(ImmOperand),
-                                             ImmOperand.getValueType());
-    } else if (auto *GA = dyn_cast<GlobalAddressSDNode>(ImmOperand)) {
-      // If the off1 in (addi base, off1) is a global variable's address (its
-      // low part, really), then we can rely on the alignment of that variable
-      // to provide a margin of safety before off1 can overflow the 12 bits.
-      // Check if off2 falls within that margin; if so off1+off2 can't overflow.
-      const DataLayout &DL = CurDAG->getDataLayout();
-      Align Alignment = GA->getGlobal()->getPointerAlignment(DL);
-      if (Offset2 != 0 && Alignment <= Offset2)
-        continue;
-      int64_t Offset1 = GA->getOffset();
-      int64_t CombinedOffset = Offset1 + Offset2;
-      ImmOperand = CurDAG->getTargetGlobalAddress(
-          GA->getGlobal(), SDLoc(ImmOperand), ImmOperand.getValueType(),
-          CombinedOffset, GA->getTargetFlags());
-    } else if (auto *CP = dyn_cast<ConstantPoolSDNode>(ImmOperand)) {
-      // Ditto.
-      Align Alignment = CP->getAlign();
-      if (Offset2 != 0 && Alignment <= Offset2)
-        continue;
-      int64_t Offset1 = CP->getOffset();
-      int64_t CombinedOffset = Offset1 + Offset2;
-      ImmOperand = CurDAG->getTargetConstantPool(
-          CP->getConstVal(), ImmOperand.getValueType(), CP->getAlign(),
-          CombinedOffset, CP->getTargetFlags());
-    } else {
-      continue;
-    }
+      return false;
+      return false;
+      return false;
+    return false;
 
-    LLVM_DEBUG(dbgs() << "Folding add-immediate into mem-op:\nBase:    ");
-    LLVM_DEBUG(Base->dump(CurDAG));
-    LLVM_DEBUG(dbgs() << "\nN: ");
-    LLVM_DEBUG(N->dump(CurDAG));
-    LLVM_DEBUG(dbgs() << "\n");
 
-    // Modify the offset operand of the load/store.
-    if (BaseOpIdx == 0) // Load
-      CurDAG->UpdateNodeOperands(N, Base.getOperand(0), ImmOperand,
-                                 N->getOperand(2));
-    else // Store
-      CurDAG->UpdateNodeOperands(N, N->getOperand(0), Base.getOperand(0),
-                                 ImmOperand, N->getOperand(3));
 
-    // The add-immediate may now be dead, in which case remove it.
-    if (Base.getNode()->use_empty())
-      CurDAG->RemoveDeadNode(Base.getNode());
-  }
+  return true;
 }
 
 // This pass converts a legalized DAG into a RISCV-specific DAG, ready
 // for instruction scheduling.
 FunctionPass *llvm::createRISCVISelDag(RISCVTargetMachine &TM) {
   return new RISCVDAGToDAGISel(TM);
 }

llvm/lib/Target/RISCV/RISCVInstrInfo.td

 let Predicates = [IsRV64] in {
 
 /// sext and zext
 
 def : Pat<(sext_inreg GPR:$rs1, i32), (ADDIW GPR:$rs1, 0)>;
 
 /// ALU operations
 
-def : Pat<(sext_inreg (add GPR:$rs1, GPR:$rs2), i32),
-          (ADDW GPR:$rs1, GPR:$rs2)>;
-def : Pat<(sext_inreg (add GPR:$rs1, simm12:$imm12), i32),
-          (ADDIW GPR:$rs1, simm12:$imm12)>;
-def : Pat<(sext_inreg (sub GPR:$rs1, GPR:$rs2), i32),
-          (SUBW GPR:$rs1, GPR:$rs2)>;
-def : Pat<(sext_inreg (shl GPR:$rs1, uimm5:$shamt), i32),
-          (SLLIW GPR:$rs1, uimm5:$shamt)>;
 def : Pat<(i64 (srl (and GPR:$rs1, 0xffffffff), uimm5:$shamt)),
           (SRLIW GPR:$rs1, uimm5:$shamt)>;
 def : Pat<(i64 (srl (shl GPR:$rs1, (i64 32)), uimm6gt32:$shamt)),
           (SRLIW GPR:$rs1, (ImmSub32 uimm6gt32:$shamt))>;
 def : Pat<(sra (sext_inreg GPR:$rs1, i32), uimm5:$shamt),
           (SRAIW GPR:$rs1, uimm5:$shamt)>;
 def : Pat<(i64 (sra (shl GPR:$rs1, (i64 32)), uimm6gt32:$shamt)),
           (SRAIW GPR:$rs1, (ImmSub32 uimm6gt32:$shamt))>;

 def : Pat<(debugtrap), (EBREAK)>;
 
 /// Simple optimization
 def : Pat<(add GPR:$rs1, (AddiPair:$rs2)),
           (ADDI (ADDI GPR:$rs1, (AddiPairImmB AddiPair:$rs2)),
                 (AddiPairImmA GPR:$rs2))>;
 
 let Predicates = [IsRV64] in {
-def : Pat<(sext_inreg (add_oneuse GPR:$rs1, (AddiPair:$rs2)), i32),
+// Select W instructions if only the lower 32-bits of the result are used.
+def : Pat<(addw GPR:$rs1, (AddiPair:$rs2)),
           (ADDIW (ADDIW GPR:$rs1, (AddiPairImmB AddiPair:$rs2)),
                  (AddiPairImmA AddiPair:$rs2))>;
 }
 
 //===----------------------------------------------------------------------===//
 // Standard extensions
 //===----------------------------------------------------------------------===//
 
 include "RISCVInstrInfoM.td"
 include "RISCVInstrInfoA.td"
 include "RISCVInstrInfoF.td"
 include "RISCVInstrInfoD.td"
 include "RISCVInstrInfoC.td"
 include "RISCVInstrInfoB.td"
 include "RISCVInstrInfoV.td"
 include "RISCVInstrInfoZfh.td"

llvm/lib/Target/RISCV/RISCVInstrInfoM.td

 } // Predicates = [HasStdExtM]
 
 def mulw : PatFrag<(ops node:$lhs, node:$rhs),
                    (mul node:$lhs, node:$rhs), [{
   return hasAllWUsers(Node);
 }]>;
 
 let Predicates = [HasStdExtM, IsRV64] in {
-def : Pat<(sext_inreg (mul GPR:$rs1, GPR:$rs2), i32),
-          (MULW GPR:$rs1, GPR:$rs2)>;
-
 // Select W instructions without sext_inreg if only the lower 32-bits of the
 // result are used.
 def : Pat<(mulw GPR:$rs1, GPR:$rs2), (MULW GPR:$rs1, GPR:$rs2)>;
 
 def : PatGprGpr<riscv_divw, DIVW>;
 def : PatGprGpr<riscv_divuw, DIVUW>;
 def : PatGprGpr<riscv_remuw, REMUW>;
 

 // Special case for calculating the full 64-bit product of a 32x32 unsigned
 // multiply where the inputs aren't known to be zero extended. We can shift the
 // inputs left by 32 and use a MULHU. This saves two SRLIs needed to finish
 // zeroing the upper 32 bits.
 // TODO: If one of the operands is zero extended and the other isn't, we might
 // still be better off shifting both left by 32.
 def : Pat<(i64 (mul (and GPR:$rs1, 0xffffffff), (and GPR:$rs2, 0xffffffff))),
           (MULHU (SLLI GPR:$rs1, 32), (SLLI GPR:$rs2, 32))>;
-// Prevent matching the first part of this pattern to mulw. The mul here has
-// additionals users or the ANDs would have been removed. The above pattern
-// will be used for the other users. If we form a mulw we'll keep the ANDs alive
-// and they'll still become SLLI+SRLI.
-def : Pat<(sext_inreg (mul (and GPR:$rs1, 0xffffffff),
-                           (and GPR:$rs2, 0xffffffff)), i32),
-          (ADDIW (MULHU (SLLI GPR:$rs1, 32), (SLLI GPR:$rs2, 32)), 0)>;
 } // Predicates = [HasStdExtM, IsRV64, NotHasStdExtZba]

llvm/test/CodeGen/RISCV/add-imm.ll

 ; RV32I-NEXT:    addi a0, a0, 1500
 ; RV32I-NEXT:    addi a0, a0, 1500
 ; RV32I-NEXT:    lui a1, %hi(gv0)
 ; RV32I-NEXT:    sw a0, %lo(gv0)(a1)
 ; RV32I-NEXT:    ret
 ;
 ; RV64I-LABEL: add32_sext_reject_on_rv64:
 ; RV64I:       # %bb.0:
-; RV64I-NEXT:    lui a1, 1
-; RV64I-NEXT:    addiw a1, a1, -1096
-; RV64I-NEXT:    addw a0, a0, a1
+; RV64I-NEXT:    addiw a0, a0, 1500
+; RV64I-NEXT:    addiw a0, a0, 1500
 ; RV64I-NEXT:    lui a1, %hi(gv0)
 ; RV64I-NEXT:    sw a0, %lo(gv0)(a1)
 ; RV64I-NEXT:    ret
   %b = add nsw i32 %a, 3000
   store i32 %b, i32* @gv0, align 4
   ret i32 %b
 }
 

llvm/test/CodeGen/RISCV/xaluo.ll

 ; RV32ZBA-NEXT:    xor a0, a3, a0
 ; RV32ZBA-NEXT:    snez a0, a0
 ; RV32ZBA-NEXT:    sw a2, 0(a1)
 ; RV32ZBA-NEXT:    ret
 ;
 ; RV64ZBA-LABEL: smulo2.i32:
 ; RV64ZBA:       # %bb.0: # %entry
 ; RV64ZBA-NEXT:    sext.w a0, a0
-; RV64ZBA-NEXT:    addi a2, zero, 13
-; RV64ZBA-NEXT:    mul a3, a0, a2
-; RV64ZBA-NEXT:    mulw a0, a0, a2
-; RV64ZBA-NEXT:    xor a0, a0, a3
+; RV64ZBA-NEXT:    sh1add a2, a0, a0
+; RV64ZBA-NEXT:    sh2add a2, a2, a0
+; RV64ZBA-NEXT:    sext.w a0, a2
+; RV64ZBA-NEXT:    xor a0, a0, a2
 ; RV64ZBA-NEXT:    snez a0, a0
-; RV64ZBA-NEXT:    sw a3, 0(a1)
+; RV64ZBA-NEXT:    sw a2, 0(a1)
 ; RV64ZBA-NEXT:    ret
 entry:
   %t = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %v1, i32 13)
   %val = extractvalue {i32, i1} %t, 0
   %obit = extractvalue {i32, i1} %t, 1
   store i32 %val, i32* %res
   ret i1 %obit
 }