[LoongArch] Assume no-op addrspacecasts by default (llvm#82332)

This PR indicates that `addrspacecasts` are always no-ops on LoongArch.

Fixes llvm#82330

(cherry picked from commit dd3e0a4)

Author: heiher

llvm/lib/Target/LoongArch/LoongArchTargetMachine.h

@@ -45,6 +45,11 @@ class LoongArchTargetMachine : public LLVMTargetMachine {
   MachineFunctionInfo *
   createMachineFunctionInfo(BumpPtrAllocator &Allocator, const Function &F,
                             const TargetSubtargetInfo *STI) const override;
+
+  // Addrspacecasts are always noops.
+  bool isNoopAddrSpaceCast(unsigned SrcAS, unsigned DestAS) const override {
+    return true;
+  }
 };
 
 } // end namespace llvm

llvm/test/CodeGen/LoongArch/addrspacecast.ll

@@ -0,0 +1,47 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc --mtriple=loongarch32 --verify-machineinstrs < %s | FileCheck %s --check-prefix=LA32
+; RUN: llc --mtriple=loongarch64 --verify-machineinstrs < %s | FileCheck %s --check-prefix=LA64
+
+define void @cast0(ptr addrspace(1) %ptr) {
+; LA32-LABEL: cast0:
+; LA32:       # %bb.0:
+; LA32-NEXT:    st.w $zero, $a0, 0
+; LA32-NEXT:    ret
+;
+; LA64-LABEL: cast0:
+; LA64:       # %bb.0:
+; LA64-NEXT:    st.w $zero, $a0, 0
+; LA64-NEXT:    ret
+  %ptr0 = addrspacecast ptr addrspace(1) %ptr to ptr addrspace(0)
+  store i32 0, ptr %ptr0
+  ret void
+}
+
+define void @cast1(ptr %ptr) {
+; LA32-LABEL: cast1:
+; LA32:       # %bb.0:
+; LA32-NEXT:    addi.w $sp, $sp, -16
+; LA32-NEXT:    .cfi_def_cfa_offset 16
+; LA32-NEXT:    st.w $ra, $sp, 12 # 4-byte Folded Spill
+; LA32-NEXT:    .cfi_offset 1, -4
+; LA32-NEXT:    bl %plt(foo)
+; LA32-NEXT:    ld.w $ra, $sp, 12 # 4-byte Folded Reload
+; LA32-NEXT:    addi.w $sp, $sp, 16
+; LA32-NEXT:    ret
+;
+; LA64-LABEL: cast1:
+; LA64:       # %bb.0:
+; LA64-NEXT:    addi.d $sp, $sp, -16
+; LA64-NEXT:    .cfi_def_cfa_offset 16
+; LA64-NEXT:    st.d $ra, $sp, 8 # 8-byte Folded Spill
+; LA64-NEXT:    .cfi_offset 1, -8
+; LA64-NEXT:    bl %plt(foo)
+; LA64-NEXT:    ld.d $ra, $sp, 8 # 8-byte Folded Reload
+; LA64-NEXT:    addi.d $sp, $sp, 16
+; LA64-NEXT:    ret
+  %castptr = addrspacecast ptr %ptr to ptr addrspace(10)
+  call void @foo(ptr addrspace(10) %castptr)
+  ret void
+}
+
+declare void @foo(ptr addrspace(10))