[BPF] fix typedef issue for offset relocation

Currently, the CO-RE offset relocation does not work
if any struct/union member or array element is a typedef.
For example,
  typedef const int arr_t[7];
  struct input {
      arr_t a;
  };
  func(...) {
       struct input *in = ...;
       ... __builtin_preserve_access_index(&in->a[1]) ...
  }
The BPF backend calculated default offset is 0 while
4 is the correct answer. Similar issues exist for struct/union
typedef's.

When getting struct/union member or array element type,
we should trace down to the type by skipping typedef
and qualifiers const/volatile as this is what clang did
to generate getelementptr instructions.
(const/volatile member type qualifiers are already
ignored by clang.)

This patch fixed this issue, for each access index,
skipping typedef and const/volatile/restrict BTF types.

Signed-off-by: Yonghong Song <yhs@fb.com>

Differential Revision: https://reviews.llvm.org/D65259

llvm-svn: 367062

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Target/BPF/BTFDebug.h b/llvm/lib/Target/BPF/BTFDebug.h
index 6c0cdde17d9..e210d18f941 100644
--- a/llvm/lib/Target/BPF/BTFDebug.h
+++ b/llvm/lib/Target/BPF/BTFDebug.h
@@ -104,11 +104,14 @@ public:
 
 /// Handle array type.
 class BTFTypeArray : public BTFTypeBase {
+  const DIType *ElemTyNoQual;
   uint32_t ElemSize;
   struct BTF::BTFArray ArrayInfo;
+  uint32_t ElemTypeNoQual;
 
 public:
-  BTFTypeArray(uint32_t ElemTypeId, uint32_t ElemSize, uint32_t NumElems);
+  BTFTypeArray(const DIType *Ty, uint32_t ElemTypeId,
+               uint32_t ElemSize, uint32_t NumElems);
   uint32_t getSize() { return BTFTypeBase::getSize() + BTF::BTFArraySize; }
   void completeType(BTFDebug &BDebug);
   void emitType(MCStreamer &OS);
@@ -120,6 +123,7 @@ class BTFTypeStruct : public BTFTypeBase {
   const DICompositeType *STy;
   bool HasBitField;
   std::vector<struct BTF::BTFMember> Members;
+  std::vector<uint32_t> MemberTypeNoQual;
 
 public:
   BTFTypeStruct(const DICompositeType *STy, bool IsStruct, bool HasBitField,