[RISCV] Fix assertion failure from performBUILD_VECTORCombine when the binop is a shift.

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -13717,7 +13717,7 @@ static SDValue performSELECTCombine(SDNode *N, SelectionDAG &DAG,
   return tryFoldSelectIntoOp(N, DAG, FalseVal, TrueVal, /*Swapped*/true);
 }
 
-/// IF we have a build_vector where each lane is binop X, C, where C
+/// If we have a build_vector where each lane is binop X, C, where C
 /// is a constant (but not necessarily the same constant on all lanes),
 /// form binop (build_vector x1, x2, ...), (build_vector c1, c2, c3, ..).
 /// We assume that materializing a constant build vector will be no more
@@ -13759,6 +13759,10 @@ static SDValue performBUILD_VECTORCombine(SDNode *N, SelectionDAG &DAG,
     if (!isa<ConstantSDNode>(Op.getOperand(1)) &&
         !isa<ConstantFPSDNode>(Op.getOperand(1)))
       return SDValue();
+    // FIXME: Return failure if the RHS type doesn't match the LHS. Shifts may
+    // have different LHS and RHS types.
+    if (Op.getOperand(0).getValueType() != Op.getOperand(1).getValueType())
+      return SDValue();
     RHSOps.push_back(Op.getOperand(1));
   }
 

llvm/test/CodeGen/RISCV/rvv/fixed-vectors-buildvec-of-binop.ll

@@ -442,3 +442,15 @@ define <4 x i32> @add_general_splat(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) {
   %v3 = insertelement <4 x i32> %v2, i32 %e3, i32 3
   ret <4 x i32> %v3
 }
+
+; This test previously failed with an assertion failure because constant shift
+; amounts are type legalized early.
+define void @buggy(i32 %0) #0 {
+entry:
+  %mul.us.us.i.3 = shl i32 %0, 1
+  %1 = insertelement <4 x i32> zeroinitializer, i32 %mul.us.us.i.3, i64 0
+  %2 = or <4 x i32> %1, <i32 1, i32 1, i32 1, i32 1>
+  %3 = shufflevector <4 x i32> %2, <4 x i32> zeroinitializer, <4 x i32> zeroinitializer
+  store <4 x i32> %3, ptr null, align 16
+  ret void
+}