From aea4339802650c1765d1cfed1c8cf3b28cb2a09b Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sat, 15 Aug 2026 03:37:35 +0800
Subject: [GlobalISel] Lower combined division and remainder

---
 backend/lib/CodeGen/GlobalISel/LegalizerHelper.cpp | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)

(limited to 'backend/lib/CodeGen/GlobalISel')

diff --git a/backend/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/backend/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 84513e6..f300680 100644
--- a/backend/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/backend/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -2966,6 +2966,9 @@ Expected<void> LegalizerHelper::lower(MachineInstr &Instruction,
   case GenericOpcode::G_SCMP:
   case GenericOpcode::G_UCMP:
     return lowerThreewayCompare(Instruction);
+  case GenericOpcode::G_SDIVREM:
+  case GenericOpcode::G_UDIVREM:
+    return lowerDivRem(Instruction);
   case GenericOpcode::G_ROTL:
   case GenericOpcode::G_ROTR:
     return lowerRotate(Instruction);
@@ -3424,6 +3427,32 @@ Expected<void> LegalizerHelper::lowerThreewayCompare(MachineInstr &Instruction)
   return Block->removeInstruction(Instruction);
 }
 
+Expected<void> LegalizerHelper::lowerDivRem(MachineInstr &Instruction) {
+  const bool IsSigned = Instruction.opcode() == opcode(GenericOpcode::G_SDIVREM);
+  const Register Quotient = *Instruction.operandAt(0)->getIf<Register>();
+  const Register Remainder = *Instruction.operandAt(1)->getIf<Register>();
+  const Register Dividend = *Instruction.operandAt(2)->getIf<Register>();
+  const Register Divisor = *Instruction.operandAt(3)->getIf<Register>();
+
+  if (auto Point = MIRBuilder.setInsertPointBefore(Instruction); !Point)
+    return std::unexpected(Point.error());
+  const GenericOpcode DivideOpcode = IsSigned ? GenericOpcode::G_SDIV : GenericOpcode::G_UDIV;
+  const GenericOpcode RemainderOpcode = IsSigned ? GenericOpcode::G_SREM : GenericOpcode::G_UREM;
+  if (auto Built = MIRBuilder.buildInstr(opcode(DivideOpcode), {Quotient}, {Dividend, Divisor});
+      !Built) {
+    return std::unexpected(Built.error());
+  }
+  if (auto Built = MIRBuilder.buildInstr(opcode(RemainderOpcode), {Remainder}, {Dividend, Divisor});
+      !Built) {
+    return std::unexpected(Built.error());
+  }
+
+  MachineBasicBlock *Block = Instruction.parent();
+  if (Block == nullptr)
+    return makeUnexpected(ErrorCode::InternalError, "DIVREM became detached during lowering");
+  return Block->removeInstruction(Instruction);
+}
+
 Expected<void> LegalizerHelper::lowerRotate(MachineInstr &Instruction) {
   const Register Destination = *Instruction.operandAt(0)->getIf<Register>();
   const Register Source = *Instruction.operandAt(1)->getIf<Register>();
-- 
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