[LoongArch] Assume no-op addrspacecasts by default

[heiher]

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

Fixes #82330

[llvmbot]

@llvm/pr-subscribers-backend-loongarch

Author: hev (heiher)

Changes

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

Fixes #82330

---

Full diff: https://github.com/llvm/llvm-project/pull/82332.diff

2 Files Affected:

• (modified) llvm/lib/Target/LoongArch/LoongArchTargetMachine.h (+5)
• (added) llvm/test/CodeGen/LoongArch/addrspacecast.ll (+47)

diff --git a/llvm/lib/Target/LoongArch/LoongArchTargetMachine.h b/llvm/lib/Target/LoongArch/LoongArchTargetMachine.h
index 7d39d47e86b363..fa9bc7608e7d2c 100644
--- a/llvm/lib/Target/LoongArch/LoongArchTargetMachine.h
+++ b/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
diff --git a/llvm/test/CodeGen/LoongArch/addrspacecast.ll b/llvm/test/CodeGen/LoongArch/addrspacecast.ll
new file mode 100644
index 00000000000000..2b90f32d029795
--- /dev/null
+++ b/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))

[SixWeining]

LGTM since currently there is no specialized address spaces on loongarch where casts aren't no-ops. If there is in future, the impl can be adjusted.