[BPF] Fix BitCast Assertion with NonZero AddrSpace (#130722)

Alexei reported a bpf selftest failure with recent llvm for bpf prog
file progs/arena_spin_lock.c. The failure only happens when clang is
built with cmake option LLVM_ENABLE_ASSERTIONS=ON.

The error message looks like:
```
 clang: /home/yhs/work/yhs/llvm-project/llvm/lib/IR/Instructions.cpp:3460:
   llvm::BitCastInst::BitCastInst(Value *, Type *, const Twine &, InsertPosition):
   Assertion `castIsValid(getOpcode(), S, Ty) && "Illegal BitCast"' failed.
```
Further investigation shows that the problem is triggered in
  BPF/BPFAbstractMemberAccess.cpp
for code
```
  auto *BCInst =
      new BitCastInst(Base, PointerType::getUnqual(BB->getContext()));
```
For the above BitCastInst, Since 'Base' has non-zero AddrSapce, the
compiler expects the type also has the same AddrSpace. But the above
PointerType::getUnqual(...) does not have AddrSpace and hence causes the
assertion failure.

Providing the proper AddrSpace for the BitCast type fixed the issue.

Co-authored-by: Yonghong Song <yonghong.song@linux.dev>

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp b/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
index 646d577..77ed246 100644
--- a/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
+++ b/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
@@ -1113,8 +1113,9 @@ bool BPFAbstractMemberAccess::transformGEPChain(CallInst *Call,
                               Call->getIterator());
 
   // Generate a BitCast
-  auto *BCInst =
-      new BitCastInst(Base, PointerType::getUnqual(BB->getContext()));
+  auto *BCInst = new BitCastInst(
+      Base, PointerType::get(BB->getContext(),
+                             Base->getType()->getPointerAddressSpace()));
   BCInst->insertBefore(Call->getIterator());
 
   // Generate a GetElementPtr