[LoongArch] Support llvm.lround intrinsics with i32 return type. (#114733)

This is needed by flang, similar to RISCV-64 in
https://reviews.llvm.org/D147195.

Author: ylzsx

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

@@ -143,6 +143,7 @@ LoongArchTargetLowering::LoongArchTargetLowering(const TargetMachine &TM,
     setOperationAction(ISD::BITREVERSE, MVT::i32, Custom);
     setOperationAction(ISD::BSWAP, MVT::i32, Custom);
     setOperationAction({ISD::UDIV, ISD::UREM}, MVT::i32, Custom);
+    setOperationAction(ISD::LROUND, MVT::i32, Custom);
   }
 
   // Set operations for LA32 only.
@@ -3107,6 +3108,18 @@ void LoongArchTargetLowering::ReplaceNodeResults(
     replaceINTRINSIC_WO_CHAINResults(N, Results, DAG, Subtarget);
     break;
   }
+  case ISD::LROUND: {
+    SDValue Op0 = N->getOperand(0);
+    EVT OpVT = Op0.getValueType();
+    RTLIB::Libcall LC =
+        OpVT == MVT::f64 ? RTLIB::LROUND_F64 : RTLIB::LROUND_F32;
+    MakeLibCallOptions CallOptions;
+    CallOptions.setTypeListBeforeSoften(OpVT, MVT::i64, true);
+    SDValue Result = makeLibCall(DAG, LC, MVT::i64, Op0, CallOptions, DL).first;
+    Result = DAG.getNode(ISD::TRUNCATE, DL, MVT::i32, Result);
+    Results.push_back(Result);
+    break;
+  }
   }
 }
 

llvm/test/CodeGen/LoongArch/double-lround.ll

@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc --mtriple=loongarch64  %s -o - | FileCheck %s
+
+declare i32 @llvm.lround.i32.f64(double)
+
+;; We support lround with i32 as return type on LoongArch64. This is needed by flang.
+define i32 @lround_i32_f64(double %a) nounwind {
+; CHECK-LABEL: lround_i32_f64:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    addi.d $sp, $sp, -16
+; CHECK-NEXT:    st.d $ra, $sp, 8 # 8-byte Folded Spill
+; CHECK-NEXT:    bl %plt(lround)
+; CHECK-NEXT:    ld.d $ra, $sp, 8 # 8-byte Folded Reload
+; CHECK-NEXT:    addi.d $sp, $sp, 16
+; CHECK-NEXT:    ret
+  %1 = call i32 @llvm.lround.i32.f64(double %a)
+  ret i32 %1
+}

llvm/test/CodeGen/LoongArch/float-lround.ll

@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc --mtriple=loongarch64 %s -o - | FileCheck %s
+
+declare i32 @llvm.lround.i32.f32(float)
+
+;; We support lround with i32 as return type on LoongArch64. This is needed by flang.
+define i32 @lround_i32_f32(float %a) nounwind {
+; CHECK-LABEL: lround_i32_f32:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    addi.d $sp, $sp, -16
+; CHECK-NEXT:    st.d $ra, $sp, 8 # 8-byte Folded Spill
+; CHECK-NEXT:    bl %plt(lroundf)
+; CHECK-NEXT:    ld.d $ra, $sp, 8 # 8-byte Folded Reload
+; CHECK-NEXT:    addi.d $sp, $sp, 16
+; CHECK-NEXT:    ret
+  %1 = call i32 @llvm.lround.i32.f32(float %a)
+  ret i32 %1
+}