Index: lib/CodeGen/GlobalISel/LegalizerHelper.cpp
===================================================================
--- lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -536,6 +536,7 @@
   }
   case TargetOpcode::G_MUL:
   case TargetOpcode::G_UMULH:
+  case TargetOpcode::G_SMULH:
     return narrowScalarMul(MI, NarrowTy);
   case TargetOpcode::G_EXTRACT:
     return narrowScalarExtract(MI, TypeIdx, NarrowTy);
@@ -2637,10 +2638,18 @@
 
   unsigned NumDstParts = DstSize / NarrowSize;
   unsigned NumSrcParts = SrcSize / NarrowSize;
-  bool IsMulHigh = MI.getOpcode() == TargetOpcode::G_UMULH;
+  bool IsMulHigh = MI.getOpcode() == TargetOpcode::G_UMULH ||
+                   MI.getOpcode() == TargetOpcode::G_SMULH;
   unsigned DstTmpParts = NumDstParts * (IsMulHigh ? 2 : 1);
 
   SmallVector<unsigned, 2> Src1Parts, Src2Parts, DstTmpRegs;
+  if (MI.getOpcode() == TargetOpcode::G_SMULH) {
+    LLT SextTy = LLT::scalar(SrcSize * 2);
+    Src1 = MRI.createGenericVirtualRegister(SextTy);
+    Src2 = MRI.createGenericVirtualRegister(SextTy);
+    MIRBuilder.buildSExt(Src1, MI.getOperand(1).getReg());
+    MIRBuilder.buildSExt(Src2, MI.getOperand(2).getReg());
+  }
   extractParts(Src1, NarrowTy, NumSrcParts, Src1Parts);
   extractParts(Src2, NarrowTy, NumSrcParts, Src2Parts);
   DstTmpRegs.resize(DstTmpParts);
@@ -2650,7 +2659,6 @@
   ArrayRef<unsigned> DstRegs(
       IsMulHigh ? &DstTmpRegs[DstTmpParts / 2] : &DstTmpRegs[0], NumDstParts);
   MIRBuilder.buildMerge(DstReg, DstRegs);
-
   MI.eraseFromParent();
   return Legalized;
 }
Index: lib/Target/Mips/MipsInstructionSelector.cpp
===================================================================
--- lib/Target/Mips/MipsInstructionSelector.cpp
+++ lib/Target/Mips/MipsInstructionSelector.cpp
@@ -143,20 +143,24 @@
   using namespace TargetOpcode;
 
   switch (I.getOpcode()) {
-  case G_UMULH: {
-    unsigned PseudoMULTuReg = MRI.createVirtualRegister(&Mips::ACC64RegClass);
-    MachineInstr *PseudoMULTu, *PseudoMove;
-
-    PseudoMULTu = BuildMI(MBB, I, I.getDebugLoc(), TII.get(Mips::PseudoMULTu))
-                      .addDef(PseudoMULTuReg)
-                      .add(I.getOperand(1))
-                      .add(I.getOperand(2));
-    if (!constrainSelectedInstRegOperands(*PseudoMULTu, TII, TRI, RBI))
+  case G_UMULH:
+  case G_SMULH: {
+    unsigned PseudoMULReg = MRI.createVirtualRegister(&Mips::ACC64RegClass);
+    bool IsSigned = I.getOpcode() == TargetOpcode::G_SMULH;
+    MachineInstr *PseudoMUL, *PseudoMove;
+
+    PseudoMUL =
+        BuildMI(MBB, I, I.getDebugLoc(),
+                TII.get(IsSigned ? Mips::PseudoMULT : Mips::PseudoMULTu))
+            .addDef(PseudoMULReg)
+            .add(I.getOperand(1))
+            .add(I.getOperand(2));
+    if (!constrainSelectedInstRegOperands(*PseudoMUL, TII, TRI, RBI))
       return false;
 
     PseudoMove = BuildMI(MBB, I, I.getDebugLoc(), TII.get(Mips::PseudoMFHI))
                      .addDef(I.getOperand(0).getReg())
-                     .addUse(PseudoMULTuReg);
+                     .addUse(PseudoMULReg);
     if (!constrainSelectedInstRegOperands(*PseudoMove, TII, TRI, RBI))
       return false;
 
Index: lib/Target/Mips/MipsLegalizerInfo.cpp
===================================================================
--- lib/Target/Mips/MipsLegalizerInfo.cpp
+++ lib/Target/Mips/MipsLegalizerInfo.cpp
@@ -31,7 +31,7 @@
   getActionDefinitionsBuilder({G_UADDO, G_UADDE, G_USUBO, G_USUBE, G_UMULO})
       .lowerFor({{s32, s1}});
 
-  getActionDefinitionsBuilder(G_UMULH)
+  getActionDefinitionsBuilder({G_UMULH, G_SMULH})
       .legalFor({s32})
       .maxScalar(0, s32);
 
Index: lib/Target/Mips/MipsRegisterBankInfo.cpp
===================================================================
--- lib/Target/Mips/MipsRegisterBankInfo.cpp
+++ lib/Target/Mips/MipsRegisterBankInfo.cpp
@@ -87,6 +87,7 @@
   case G_SUB:
   case G_MUL:
   case G_UMULH:
+  case G_SMULH:
   case G_LOAD:
   case G_STORE:
   case G_ZEXTLOAD: