Fix shl crash

Author: lukel97

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -2269,8 +2269,10 @@ Instruction *InstCombinerImpl::foldVectorBinop(BinaryOperator &Inst) {
       // It may not be safe to execute a binop on a vector with poison elements
       // because the entire instruction can be folded to undef or create poison
       // that did not exist in the original code.
+      // This isn't needed for scalable vectors since they're always splats.
       // TODO: The shift case should not be necessary.
-      if (Inst.isIntDivRem() || (Inst.isShift() && ConstOp1))
+      if (isa<FixedVectorType>(V1->getType()) &&
+          (Inst.isIntDivRem() || (Inst.isShift() && ConstOp1)))
         NewC = getSafeVectorConstantForBinop(Opcode, NewC, ConstOp1);
 
       // Op(shuffle(V1, Mask), C) -> shuffle(Op(V1, NewC), Mask)

llvm/test/Transforms/InstCombine/vec_shuffle.ll

@@ -938,6 +938,28 @@ define <2 x i32> @shl_splat_constant1(<2 x i32> %x) {
   ret <2 x i32> %r
 }
 
+define <vscale x 2 x i32> @shl_splat_constant0_scalable(<vscale x 2 x i32> %x) {
+; CHECK-LABEL: @shl_splat_constant0_scalable(
+; CHECK-NEXT:    [[TMP1:%.*]] = shl <vscale x 2 x i32> splat (i32 5), [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = shufflevector <vscale x 2 x i32> [[TMP1]], <vscale x 2 x i32> poison, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT:    ret <vscale x 2 x i32> [[R]]
+;
+  %splat = shufflevector <vscale x 2 x i32> %x, <vscale x 2 x i32> undef, <vscale x 2 x i32> zeroinitializer
+  %r = shl <vscale x 2 x i32> splat (i32 5), %splat
+  ret <vscale x 2 x i32> %r
+}
+
+define <vscale x 2 x i32> @shl_splat_constant1_scalable(<vscale x 2 x i32> %x) {
+; CHECK-LABEL: @shl_splat_constant1_scalable(
+; CHECK-NEXT:    [[TMP1:%.*]] = shl <vscale x 2 x i32> [[X:%.*]], splat (i32 5)
+; CHECK-NEXT:    [[R:%.*]] = shufflevector <vscale x 2 x i32> [[TMP1]], <vscale x 2 x i32> poison, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT:    ret <vscale x 2 x i32> [[R]]
+;
+  %splat = shufflevector <vscale x 2 x i32> %x, <vscale x 2 x i32> undef, <vscale x 2 x i32> zeroinitializer
+  %r = shl <vscale x 2 x i32> %splat, splat (i32 5)
+  ret <vscale x 2 x i32> %r
+}
+
 define <2 x i32> @ashr_splat_constant0(<2 x i32> %x) {
 ; CHECK-LABEL: @ashr_splat_constant0(
 ; CHECK-NEXT:    [[TMP1:%.*]] = lshr <2 x i32> <i32 5, i32 poison>, [[X:%.*]]