Reworked and fixed.

Author: JonPsson1

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

@@ -7218,12 +7218,21 @@ SDValue SystemZTargetLowering::combineSTORE(
 
     // Find a replicated immediate and return it if found in Word and its
     // type in WordVT.
-    auto FindReplicatedImm = [&](ConstantSDNode *C) {
+    auto FindReplicatedImm = [&](ConstantSDNode *C, unsigned TotBytes) {
       // Some constants are better handled with a scalar store.
       if (C->getAPIntValue().getBitWidth() > 64 || C->isAllOnes() ||
           isInt<16>(C->getSExtValue()) || MemVT.getStoreSize() <= 2)
         return;
-      SystemZVectorConstantInfo VCI(C->getAPIntValue());
+
+      APInt Val = C->getAPIntValue();
+      // Truncate Val in case of a truncating store.
+      if (!llvm::isUIntN(TotBytes * 8, Val.getZExtValue())) {
+        assert(SN->isTruncatingStore() &&
+               "Non-truncating store and immediate value does not fit?");
+        Val = Val.trunc(TotBytes * 8);
+      }
+
+      SystemZVectorConstantInfo VCI(Val);
       if (VCI.isVectorConstantLegal(Subtarget) &&
           VCI.Opcode == SystemZISD::REPLICATE) {
         Word = DAG.getConstant(VCI.OpVals[0], SDLoc(SN), MVT::i32);
@@ -7261,12 +7270,12 @@ SDValue SystemZTargetLowering::combineSTORE(
         DAG.isSplatValue(Op1, true/*AllowUndefs*/)) {
       SDValue SplatVal = Op1->getOperand(0);
       if (auto *C = dyn_cast<ConstantSDNode>(SplatVal))
-        FindReplicatedImm(C);
+        FindReplicatedImm(C, SplatVal.getValueType().getStoreSize());
       else
         FindReplicatedReg(SplatVal);
     } else {
       if (auto *C = dyn_cast<ConstantSDNode>(Op1))
-        FindReplicatedImm(C);
+        FindReplicatedImm(C, MemVT.getStoreSize());
       else
         FindReplicatedReg(Op1);
     }

llvm/test/CodeGen/SystemZ/dag-combine-07.ll

@@ -16,7 +16,7 @@ define void @func_5(ptr %Dst) {
 ; CHECK-NEXT:    stg %r0, 0(%r1)
 ; CHECK-NEXT:    lgrl %r1, G1@GOT
 ; CHECK-NEXT:    stg %r0, 0(%r1)
-; CHECK-NEXT:    st %r0, 0(%r2)
+; CHECK-NEXT:    mvhi 0(%r2), 2
 ; CHECK-NEXT:    br %r14
   store i64 214748364802, ptr @G2, align 8
   store i64 214748364802, ptr @G1, align 8