[LoongArch] Override TargetSubtargetInfo::getSelectionDAGInfo

[wangleiat]

Summary

The target selection DAG lowering information is needed for
SelectionDAGBuilder to lower a call like memcmp into an optimized
form.

[xen0n]

Cross-checked with RISCV codegen, looks okay ;-)

llvm/lib/Target/LoongArch/LoongArchSubtarget.h

class LoongArchSubtarget : public LoongArchGenSubtargetInfo {
   bool HasExtLBT = false;
   unsigned GRLen = 32;
   MVT GRLenVT = MVT::i32;
   LoongArchABI::ABI TargetABI = LoongArchABI::ABI_Unknown;
   LoongArchFrameLowering FrameLowering;
   LoongArchInstrInfo InstrInfo;
   LoongArchRegisterInfo RegInfo;
   LoongArchTargetLowering TLInfo;
+  SelectionDAGTargetInfo TSInfo;
 
   /// Initializes using the passed in CPU and feature strings so that we can
   /// use initializer lists for subtarget initialization.
   LoongArchSubtarget &initializeSubtargetDependencies(const Triple &TT,
                                                       StringRef CPU,
                                                       StringRef TuneCPU,
                                                       StringRef FS,
                                                       StringRef ABIName);
public:
   }
   const LoongArchInstrInfo *getInstrInfo() const override { return &InstrInfo; }
   const LoongArchRegisterInfo *getRegisterInfo() const override {
     return &RegInfo;
   }
   const LoongArchTargetLowering *getTargetLowering() const override {
     return &TLInfo;
   }
+  const SelectionDAGTargetInfo *getSelectionDAGInfo() const override {
+    return &TSInfo;
+  }
   bool is64Bit() const { return HasLA64; }
   bool hasBasicF() const { return HasBasicF; }
   bool hasBasicD() const { return HasBasicD; }
   bool hasExtLSX() const { return HasExtLSX; }
   bool hasExtLASX() const { return HasExtLASX; }
   bool hasExtLVZ() const { return HasExtLVZ; }
   bool hasExtLBT() const { return HasExtLBT; }
   MVT getGRLenVT() const { return GRLenVT; }
   unsigned getGRLen() const { return GRLen; }
   LoongArchABI::ABI getTargetABI() const { return TargetABI; }
 };
 } // end namespace llvm
 
 #endif // LLVM_LIB_TARGET_LOONGARCH_LOONGARCHSUBTARGET_H

llvm/test/CodeGen/LoongArch/memcmp.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc --mtriple=loongarch64 < %s | FileCheck %s
+
+;; Before getSelectionDAGInfo() interface hooks were defined DAGBuilder
+;; would crash.
+
+define signext i32 @test1(ptr %buffer1, ptr %buffer2) {
+; CHECK-LABEL: test1:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    addi.d $sp, $sp, -16
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    st.d $ra, $sp, 8 # 8-byte Folded Spill
+; CHECK-NEXT:    .cfi_offset 1, -8
+; CHECK-NEXT:    ori $a2, $zero, 16
+; CHECK-NEXT:    bl %plt(memcmp)
+; CHECK-NEXT:    ld.d $ra, $sp, 8 # 8-byte Folded Reload
+; CHECK-NEXT:    addi.d $sp, $sp, 16
+; CHECK-NEXT:    ret
+entry:
+  %call = call signext i32 @memcmp(ptr %buffer1, ptr %buffer2, i64 16)
+  ret i32 %call
+}
+
+declare signext i32 @memcmp(ptr, ptr, i64)