[LoongArch] Expand fptrunc store from f64 to f32

[xen0n]

Very straightforward.

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

if (Subtarget.hasBasicD()) {
     setOperationAction(ISD::FMA, MVT::f64, Legal);
     setOperationAction(ISD::FMINNUM_IEEE, MVT::f64, Legal);
     setOperationAction(ISD::FMAXNUM_IEEE, MVT::f64, Legal);
     setOperationAction(ISD::FSIN, MVT::f64, Expand);
     setOperationAction(ISD::FCOS, MVT::f64, Expand);
     setOperationAction(ISD::FSINCOS, MVT::f64, Expand);
     setOperationAction(ISD::FPOW, MVT::f64, Expand);
     setOperationAction(ISD::FREM, MVT::f64, Expand);
+    setTruncStoreAction(MVT::f64, MVT::f32, Expand);
   }
 
   setOperationAction(ISD::BR_JT, MVT::Other, Expand);
 
   setOperationAction(ISD::BR_CC, GRLenVT, Expand);
   setOperationAction(ISD::SELECT_CC, GRLenVT, Expand);
   setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);
   setOperationAction({ISD::SMUL_LOHI, ISD::UMUL_LOHI}, GRLenVT, Expand);

llvm/test/CodeGen/LoongArch/fp-trunc-store.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc --mtriple=loongarch32 --mattr=+f,-d < %s | FileCheck %s --check-prefix=LA32F
+; RUN: llc --mtriple=loongarch32 --mattr=+d < %s | FileCheck %s --check-prefix=LA32D
+; RUN: llc --mtriple=loongarch64 --mattr=+f,-d < %s | FileCheck %s --check-prefix=LA64F
+; RUN: llc --mtriple=loongarch64 --mattr=+d < %s | FileCheck %s --check-prefix=LA64D
+
+define void @fp_trunc(ptr %a, double %b) nounwind {
+; LA32F-LABEL: fp_trunc:
+; LA32F:       # %bb.0:
+; LA32F-NEXT:    addi.w $sp, $sp, -16
+; LA32F-NEXT:    st.w $ra, $sp, 12 # 4-byte Folded Spill
+; LA32F-NEXT:    st.w $fp, $sp, 8 # 4-byte Folded Spill
+; LA32F-NEXT:    move $fp, $a0
+; LA32F-NEXT:    move $a0, $a1
+; LA32F-NEXT:    move $a1, $a2
+; LA32F-NEXT:    bl %plt(__truncdfsf2)
+; LA32F-NEXT:    fst.s $fa0, $fp, 0
+; LA32F-NEXT:    ld.w $fp, $sp, 8 # 4-byte Folded Reload
+; LA32F-NEXT:    ld.w $ra, $sp, 12 # 4-byte Folded Reload
+; LA32F-NEXT:    addi.w $sp, $sp, 16
+; LA32F-NEXT:    ret
+;
+; LA32D-LABEL: fp_trunc:
+; LA32D:       # %bb.0:
+; LA32D-NEXT:    fcvt.s.d $fa0, $fa0
+; LA32D-NEXT:    fst.s $fa0, $a0, 0
+; LA32D-NEXT:    ret
+;
+; LA64F-LABEL: fp_trunc:
+; LA64F:       # %bb.0:
+; LA64F-NEXT:    addi.d $sp, $sp, -16
+; LA64F-NEXT:    st.d $ra, $sp, 8 # 8-byte Folded Spill
+; LA64F-NEXT:    st.d $fp, $sp, 0 # 8-byte Folded Spill
+; LA64F-NEXT:    move $fp, $a0
+; LA64F-NEXT:    move $a0, $a1
+; LA64F-NEXT:    bl %plt(__truncdfsf2)
+; LA64F-NEXT:    fst.s $fa0, $fp, 0
+; LA64F-NEXT:    ld.d $fp, $sp, 0 # 8-byte Folded Reload
+; LA64F-NEXT:    ld.d $ra, $sp, 8 # 8-byte Folded Reload
+; LA64F-NEXT:    addi.d $sp, $sp, 16
+; LA64F-NEXT:    ret
+;
+; LA64D-LABEL: fp_trunc:
+; LA64D:       # %bb.0:
+; LA64D-NEXT:    fcvt.s.d $fa0, $fa0
+; LA64D-NEXT:    fst.s $fa0, $a0, 0
+; LA64D-NEXT:    ret
+  %1 = fptrunc double %b to float
+  store float %1, ptr %a, align 4
+  ret void
+}