diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index d8bcc59..a9af31f 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -1675,7 +1675,15 @@
   case TargetOpcode::G_CONSTANT: {
     MachineOperand &SrcMO = MI.getOperand(1);
     LLVMContext &Ctx = MIRBuilder.getMF().getFunction().getContext();
-    const APInt &Val = SrcMO.getCImm()->getValue().sext(WideTy.getSizeInBits());
+    unsigned ExtOpc = LI.getExtOpcodeForWideningConstant(
+        MRI.getType(MI.getOperand(0).getReg()));
+    assert((ExtOpc == TargetOpcode::G_ZEXT || ExtOpc == TargetOpcode::G_SEXT ||
+            ExtOpc == TargetOpcode::G_ANYEXT) &&
+           "Illegal Extend");
+    const APInt &SrcVal = SrcMO.getCImm()->getValue();
+    const APInt &Val = (ExtOpc == TargetOpcode::G_SEXT)
+                           ? SrcVal.sext(WideTy.getSizeInBits())
+                           : SrcVal.zext(WideTy.getSizeInBits());
     Observer.changingInstr(MI);
     SrcMO.setCImm(ConstantInt::get(Ctx, Val));
 
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
index 7004551..f897f9c 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
@@ -685,6 +685,10 @@
   return true;
 }
 
+unsigned LegalizerInfo::getExtOpcodeForWideningConstant(LLT SmallTy) const {
+  return SmallTy.isByteSized() ? TargetOpcode::G_SEXT : TargetOpcode::G_ZEXT;
+}
+
 /// \pre Type indices of every opcode form a dense set starting from 0.
 void LegalizerInfo::verify(const MCInstrInfo &MII) const {
 #ifndef NDEBUG