[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 <[email protected]>

Author: yonghong-song

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

llvm/test/CodeGen/BPF/CORE/arena_bitcast.ll

@@ -0,0 +1,80 @@
+; RUN: opt -O2 %s | llvm-dis > %t1
+; RUN: llc -mcpu=v3 -filetype=asm -o - %t1 | FileCheck %s
+; Source code:
+;   struct lock_t {
+;     int counter;
+;   } __attribute__((preserve_access_index));
+;
+;   #define __arena __attribute__((address_space(1)))
+;   int test(struct lock_t __arena *lock, unsigned val)
+;   {
+;     return __sync_val_compare_and_swap((&lock->counter), val, 1);
+;   }
+; Compilation flag:
+;   clang -target bpf -O2 -g -S -emit-llvm -Xclang -disable-llvm-passes arena_bitcast.c
+
+target triple = "bpf"
+
+%struct.lock_t = type { i32 }
+
+; Function Attrs: nounwind
+define dso_local i32 @test(ptr addrspace(1) noundef %lock, i32 noundef %val) #0 !dbg !7 {
+entry:
+  %lock.addr = alloca ptr addrspace(1), align 8
+  %val.addr = alloca i32, align 4
+  store ptr addrspace(1) %lock, ptr %lock.addr, align 8, !tbaa !19
+    #dbg_declare(ptr %lock.addr, !17, !DIExpression(), !24)
+  store i32 %val, ptr %val.addr, align 4, !tbaa !25
+    #dbg_declare(ptr %val.addr, !18, !DIExpression(), !27)
+  %0 = load ptr addrspace(1), ptr %lock.addr, align 8, !dbg !28, !tbaa !19
+  %1 = call ptr addrspace(1) @llvm.preserve.struct.access.index.p1.p1(ptr addrspace(1) elementtype(%struct.lock_t) %0, i32 0, i32 0), !dbg !29, !llvm.preserve.access.index !12
+  %2 = load i32, ptr %val.addr, align 4, !dbg !30, !tbaa !25
+  %3 = cmpxchg ptr addrspace(1) %1, i32 %2, i32 1 seq_cst seq_cst, align 4, !dbg !31
+  %4 = extractvalue { i32, i1 } %3, 0, !dbg !31
+  ret i32 %4, !dbg !32
+}
+; CHECK:  r1 = addr_space_cast(r1, 0, 1)
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(none)
+declare ptr addrspace(1) @llvm.preserve.struct.access.index.p1.p1(ptr addrspace(1), i32 immarg, i32 immarg) #1
+
+attributes #0 = { nounwind "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #1 = { nocallback nofree nosync nounwind willreturn memory(none) }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 21.0.0git (https://github.com/llvm/llvm-project.git 7d4d8509cbec7eecd8aaf2510015b54bc5c173e1)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "arena_bitcast.c", directory: "/root/home/yhs/tests/arena/simple", checksumkind: CSK_MD5, checksum: "51cb51c1fc09d3033dbd9aee9044dc9b")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 7, !"frame-pointer", i32 2}
+!6 = !{!"clang version 21.0.0git (https://github.com/llvm/llvm-project.git 7d4d8509cbec7eecd8aaf2510015b54bc5c173e1)"}
+!7 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 6, type: !8, scopeLine: 7, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !16)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !11, !15}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !12, size: 64)
+!12 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "lock_t", file: !1, line: 1, size: 32, elements: !13)
+!13 = !{!14}
+!14 = !DIDerivedType(tag: DW_TAG_member, name: "counter", scope: !12, file: !1, line: 2, baseType: !10, size: 32)
+!15 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!16 = !{!17, !18}
+!17 = !DILocalVariable(name: "lock", arg: 1, scope: !7, file: !1, line: 6, type: !11)
+!18 = !DILocalVariable(name: "val", arg: 2, scope: !7, file: !1, line: 6, type: !15)
+!19 = !{!20, !20, i64 0}
+!20 = !{!"p1 _ZTS6lock_t", !21, i64 0}
+!21 = !{!"any pointer", !22, i64 0}
+!22 = !{!"omnipotent char", !23, i64 0}
+!23 = !{!"Simple C/C++ TBAA"}
+!24 = !DILocation(line: 6, column: 33, scope: !7)
+!25 = !{!26, !26, i64 0}
+!26 = !{!"int", !22, i64 0}
+!27 = !DILocation(line: 6, column: 48, scope: !7)
+!28 = !DILocation(line: 8, column: 40, scope: !7)
+!29 = !DILocation(line: 8, column: 46, scope: !7)
+!30 = !DILocation(line: 8, column: 56, scope: !7)
+!31 = !DILocation(line: 8, column: 10, scope: !7)
+!32 = !DILocation(line: 8, column: 3, scope: !7)