lattigo: fix _ := foo emitter bug

PiperOrigin-RevId: 918498275

Author: j2kun

lib/Target/Lattigo/LattigoEmitter.cpp

@@ -328,7 +328,12 @@ LogicalResult LattigoEmitter::printOperation(affine::AffineForOp op) {
   for (auto i = 0; i < op.getNumRegionIterArgs(); ++i) {
     Value opResult = op.getResult(i);
     Value iterArg = op.getRegionIterArgs()[i];
-    os << getName(opResult) << " := " << getName(iterArg) << "\n";
+    std::string resultName = getName(opResult);
+    if (resultName == "_") {
+      os << resultName << " = " << getName(iterArg) << "\n";
+    } else {
+      os << resultName << " := " << getName(iterArg) << "\n";
+    }
   }
   return success();
 }
@@ -970,7 +975,12 @@ LogicalResult LattigoEmitter::printOperation(scf::ForOp op) {
   for (int i = 0; i < op.getNumResults(); ++i) {
     Value opResult = op.getResult(i);
     Value iterArg = op.getRegionIterArg(i);
-    os << getName(opResult) << " := " << getName(iterArg) << "\n";
+    std::string resultName = getName(opResult);
+    if (resultName == "_") {
+      os << resultName << " = " << getName(iterArg) << "\n";
+    } else {
+      os << resultName << " := " << getName(iterArg) << "\n";
+    }
   }
   return success();
 }

tests/Emitter/Lattigo/emit_loops.mlir

@@ -73,4 +73,43 @@ module attributes {scheme.bgv} {
     }
     return %1 : !ct
   }
+  // CHECK: test_affine_for_unused_result
+  // CHECK-SAME: [[ct_init:[^ ]*]] *rlwe.Ciphertext
+  // CHECK: [[iter_arg:[^ ]*]] := [[ct_init]]
+  // CHECK: for [[induction_var:[^ ]*]] := 1; [[induction_var]] < 10; [[induction_var]] += 2 {
+  // CHECK:   [[op_result:[^ ,]*]], [[err0:[^ ]*]] := evaluator.RotateColumnsNew([[iter_arg]], 1)
+  // CHECK:   [[iter_arg]] = [[op_result]]
+  // CHECK: }
+  // CHECK: _ = [[iter_arg]]
+  // CHECK: return
+  func.func @test_affine_for_unused_result(%evaluator: !evaluator, %ct: !ct) {
+    %1 = affine.for %arg0 = 1 to 10 step 2 iter_args(%arg1 = %ct) -> (!ct) {
+      %ct_12 = lattigo.bgv.rotate_columns_new %evaluator, %arg1 {static_shift = 1} : (!evaluator, !ct) -> !ct
+      affine.yield %ct_12 : !ct
+    }
+    return
+  }
+
+  // CHECK: test_scf_for_unused_result
+  // CHECK-SAME: [[ct_init:[^ ]*]] *rlwe.Ciphertext
+  // CHECK: [[c1:[^ ]*]] := int64(1)
+  // CHECK: [[c10:[^ ]*]] := int64(10)
+  // CHECK: [[c2:[^ ]*]] := int64(2)
+  // CHECK: [[iter_arg:[^ ]*]] := [[ct_init]]
+  // CHECK: for [[induction_var:[^ ]*]] := [[c1]]; [[induction_var]] < [[c10]]; [[induction_var]] += [[c2]] {
+  // CHECK:   [[op_result:[^ ,]*]], [[err0:[^ ]*]] := evaluator.RotateColumnsNew([[iter_arg]], 1)
+  // CHECK:   [[iter_arg]] = [[op_result]]
+  // CHECK: }
+  // CHECK: _ = [[iter_arg]]
+  // CHECK: return
+  func.func @test_scf_for_unused_result(%evaluator: !evaluator, %ct: !ct) {
+    %c1 = arith.constant 1 : index
+    %c10 = arith.constant 10 : index
+    %c2 = arith.constant 2 : index
+    %1 = scf.for %arg0 = %c1 to %c10 step %c2 iter_args(%arg1 = %ct) -> (!ct) {
+      %ct_12 = lattigo.bgv.rotate_columns_new %evaluator, %arg1 {static_shift = 1} : (!evaluator, !ct) -> !ct
+      scf.yield %ct_12 : !ct
+    }
+    return
+  }
 }