diff --git a/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp b/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
--- a/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
@@ -11,11 +11,13 @@
 /// \todo This should be generated by TableGen.
 //===----------------------------------------------------------------------===//
 
+#include "MCTargetDesc/RISCVMatInt.h"
 #include "RISCVRegisterBankInfo.h"
 #include "RISCVSubtarget.h"
 #include "RISCVTargetMachine.h"
 #include "llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h"
 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
+#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
 #include "llvm/IR/IntrinsicsRISCV.h"
 #include "llvm/Support/Debug.h"
 
@@ -35,7 +37,9 @@
                            const RISCVSubtarget &STI,
                            const RISCVRegisterBankInfo &RBI);
 
-  bool select(MachineInstr &I) override;
+  bool select(MachineInstr &MI) override;
+  bool selectConstant(MachineInstr &MI, MachineIRBuilder &MIB,
+                      MachineRegisterInfo &MRI);
   static const char *getName() { return DEBUG_TYPE; }
 
 private:
@@ -80,17 +84,91 @@
 {
 }
 
-bool RISCVInstructionSelector::select(MachineInstr &I) {
+bool RISCVInstructionSelector::select(MachineInstr &MI) {
+  unsigned Opc = MI.getOpcode();
+  MachineBasicBlock &MBB = *MI.getParent();
+  MachineFunction &MF = *MBB.getParent();
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+  MachineIRBuilder MIB(MF);
 
-  if (!isPreISelGenericOpcode(I.getOpcode())) {
+  if (!isPreISelGenericOpcode(MI.getOpcode())) {
     // Certain non-generic instructions also need some special handling.
     return true;
   }
 
-  if (selectImpl(I, *CoverageInfo))
+  if (selectImpl(MI, *CoverageInfo))
     return true;
 
-  return false;
+  MIB.setInstrAndDebugLoc(MI);
+
+  switch (Opc) {
+  case TargetOpcode::G_CONSTANT:
+    if (!selectConstant(MI, MIB, MRI))
+      return false;
+    break;
+  default:
+    return false;
+  }
+
+  MI.eraseFromParent();
+
+  return true;
+}
+
+bool RISCVInstructionSelector::selectConstant(MachineInstr &MI,
+                                              MachineIRBuilder &MIB,
+                                              MachineRegisterInfo &MRI) {
+  assert(MI.getOpcode() == TargetOpcode::G_CONSTANT);
+  Register FinalReg = MI.getOperand(0).getReg();
+  int64_t Imm = MI.getOperand(1).getCImm()->getSExtValue();
+
+  RISCVMatInt::InstSeq Seq =
+      RISCVMatInt::generateInstSeq(Imm, Subtarget->getFeatureBits());
+  unsigned NumInsts = Seq.size();
+  Register SrcReg = RISCV::X0;
+
+  for (unsigned i = 0; i < NumInsts; i++) {
+    Register DstReg = i < NumInsts - 1
+                          ? MRI.createVirtualRegister(&RISCV::GPRRegClass)
+                          : FinalReg;
+    const RISCVMatInt::Inst I = Seq[i];
+    MachineInstr *Result;
+
+    switch (I.getOpndKind()) {
+    case RISCVMatInt::Imm:
+      // clang-format off
+      Result = MIB.buildInstr(I.getOpcode())
+                   .addDef(DstReg)
+                   .addImm(I.getImm());
+      // clang-format on
+      break;
+    case RISCVMatInt::RegX0:
+      Result = MIB.buildInstr(I.getOpcode())
+                   .addDef(DstReg)
+                   .addReg(SrcReg)
+                   .addReg(RISCV::X0);
+      break;
+    case RISCVMatInt::RegReg:
+      Result = MIB.buildInstr(I.getOpcode())
+                   .addDef(DstReg)
+                   .addReg(SrcReg)
+                   .addReg(SrcReg);
+      break;
+    case RISCVMatInt::RegImm:
+      Result = MIB.buildInstr(I.getOpcode())
+                   .addDef(DstReg)
+                   .addReg(SrcReg)
+                   .addImm(I.getImm());
+      break;
+    }
+
+    if (!constrainSelectedInstRegOperands(*Result, TII, TRI, RBI))
+      return false;
+
+    SrcReg = DstReg;
+  }
+
+  return true;
 }
 
 namespace llvm {
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/constant32.mir b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/constant32.mir
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/constant32.mir
@@ -0,0 +1,125 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv32 -run-pass=instruction-select %s -o - \
+# RUN: | FileCheck %s
+---
+name:            const_i32_INT_MIN
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i32_INT_MIN
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[LUI:%[0-9]+]]:gpr = LUI 524288
+    ; CHECK-NEXT: $x10 = COPY [[LUI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s32) = G_CONSTANT i32 -2147483648
+    $x10 = COPY %0(s32)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i32_neg_2147483000
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i32_neg_2147483000
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[LUI:%[0-9]+]]:gpr = LUI 524288
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI [[LUI]], 648
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s32) = G_CONSTANT i32 -2147483000
+    $x10 = COPY %0(s32)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i32_INT_MAX
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i32_INT_MAX
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[LUI:%[0-9]+]]:gpr = LUI 524288
+    ; CHECK-NEXT: $x10 = COPY [[LUI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s32) = G_CONSTANT i32 2147483648
+    $x10 = COPY %0(s32)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i32_2147483000
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i32_2147483000
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[LUI:%[0-9]+]]:gpr = LUI 524288
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI [[LUI]], -648
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s32) = G_CONSTANT i32 2147483000
+    $x10 = COPY %0(s32)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i32_256
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i32_256
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, 256
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s32) = G_CONSTANT i32 256
+    $x10 = COPY %0(s32)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i32_0
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i32_0
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, 0
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s32) = G_CONSTANT i32 0
+    $x10 = COPY %0(s32)
+    PseudoRET implicit $x10
+
+...
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/constant64.mir b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/constant64.mir
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/constant64.mir
@@ -0,0 +1,128 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv64 -run-pass=instruction-select %s -o - \
+# RUN: | FileCheck %s
+---
+name:            const_i64_INT_MIN
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i64_INT_MIN
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, -1
+    ; CHECK-NEXT: [[SLLI:%[0-9]+]]:gpr = SLLI [[ADDI]], 63
+    ; CHECK-NEXT: $x10 = COPY [[SLLI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = G_CONSTANT i64 -9223372036854775808
+    $x10 = COPY %0(s64)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i64_neg_9223372036854775000
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i64_neg_9223372036854775000
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, -1
+    ; CHECK-NEXT: [[SLLI:%[0-9]+]]:gpr = SLLI [[ADDI]], 63
+    ; CHECK-NEXT: [[ADDI1:%[0-9]+]]:gpr = ADDI [[SLLI]], 808
+    ; CHECK-NEXT: $x10 = COPY [[ADDI1]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = G_CONSTANT i64 -9223372036854775000
+    $x10 = COPY %0(s64)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i64_INT_MAX
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i64_INT_MAX
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, -1
+    ; CHECK-NEXT: [[SRLI:%[0-9]+]]:gpr = SRLI [[ADDI]], 1
+    ; CHECK-NEXT: $x10 = COPY [[SRLI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = G_CONSTANT i64 9223372036854775807
+    $x10 = COPY %0(s64)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i64_9223372036854775000
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i64_9223372036854775000
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, -1615
+    ; CHECK-NEXT: [[SRLI:%[0-9]+]]:gpr = SRLI [[ADDI]], 1
+    ; CHECK-NEXT: $x10 = COPY [[SRLI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = G_CONSTANT i64 9223372036854775000
+    $x10 = COPY %0(s64)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i64_256
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i64_256
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, 256
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = G_CONSTANT i64 256
+    $x10 = COPY %0(s64)
+    PseudoRET implicit $x10
+
+...
+---
+name:            const_i64_0
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:            |
+  bb.0:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: const_i64_0
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[ADDI:%[0-9]+]]:gpr = ADDI $x0, 0
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = G_CONSTANT i64 0
+    $x10 = COPY %0(s64)
+    PseudoRET implicit $x10
+
+...