[clang] 9271cab - [BPF] use base lvalue type for preserve_{struct, union}_access_index metadata

[Yonghong Song via cfe-commits]

Author: Yonghong Song
Date: 2020-02-04T09:28:30-08:00
New Revision: 9271cab270a52b5200ef45a16f1a9d9baaccaba0

URL: https://github.com/llvm/llvm-project/commit/9271cab270a52b5200ef45a16f1a9d9baaccaba0
DIFF: https://github.com/llvm/llvm-project/commit/9271cab270a52b5200ef45a16f1a9d9baaccaba0.diff

LOG: [BPF] use base lvalue type for preserve_{struct,union}_access_index metadata

Linux commit
  https://github.com/torvalds/linux/commit/1cf5b23988ea0086a252a5c8b005b075f1e9b030#diff-289313b9fec99c6f0acfea19d9cfd949
uses "#pragma clang attribute push (__attribute__((preserve_access_index)),
      apply_to = record)"
to apply CO-RE relocations to all records including the following pattern:
  #pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
  typedef struct {
    int a;
  } __t;
  #pragma clang attribute pop
  int test(__t *arg) { return arg->a; }

The current approach to use struct type in the relocation record will
result in an anonymous struct, which make later type matching difficult
    in bpf loader. In fact, current BPF backend will fail the above program
with assertion:
  clang: ../lib/Target/BPF/BPFAbstractMemberAccess.cpp:796: ...
     Assertion `TypeName.size()' failed.

The patch use the base lvalue type for the "base" value to annotate
preservee_{struct,union}_access_index intrinsics. In the above example,
the type will be "__t" which preserved the type name.

Differential Revision: https://reviews.llvm.org/D73900

Added: 
    clang/test/CodeGen/builtin-preserve-access-index-typedef.c

Modified: 
    clang/lib/CodeGen/CGExpr.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 4b8a31c180c8..17fc16a1fe5b 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -4024,17 +4024,17 @@ static Address emitAddrOfFieldStorage(CodeGenFunction &CGF, Address base,
   return CGF.Builder.CreateStructGEP(base, idx, field->getName());
 }
 
-static Address emitPreserveStructAccess(CodeGenFunction &CGF, Address base,
-                                        const FieldDecl *field) {
+static Address emitPreserveStructAccess(CodeGenFunction &CGF, LValue base,
+                                        Address addr, const FieldDecl *field) {
   const RecordDecl *rec = field->getParent();
-  llvm::DIType *DbgInfo = CGF.getDebugInfo()->getOrCreateRecordType(
-      CGF.getContext().getRecordType(rec), rec->getLocation());
+  llvm::DIType *DbgInfo = CGF.getDebugInfo()->getOrCreateStandaloneType(
+      base.getType(), rec->getLocation());
 
   unsigned idx =
       CGF.CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
 
   return CGF.Builder.CreatePreserveStructAccessIndex(
-      base, idx, CGF.getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo);
+      addr, idx, CGF.getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo);
 }
 
 static bool hasAnyVptr(const QualType Type, const ASTContext &Context) {
@@ -4158,8 +4158,8 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
     if (IsInPreservedAIRegion ||
         (getDebugInfo() && rec->hasAttr<BPFPreserveAccessIndexAttr>())) {
       // Remember the original union field index
-      llvm::DIType *DbgInfo = getDebugInfo()->getOrCreateRecordType(
-          getContext().getRecordType(rec), rec->getLocation());
+      llvm::DIType *DbgInfo = getDebugInfo()->getOrCreateStandaloneType(base.getType(),
+          rec->getLocation());
       addr = Address(
           Builder.CreatePreserveUnionAccessIndex(
               addr.getPointer(), getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo),
@@ -4176,7 +4176,7 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
       addr = emitAddrOfFieldStorage(*this, addr, field);
     else
       // Remember the original struct field index
-      addr = emitPreserveStructAccess(*this, addr, field);
+      addr = emitPreserveStructAccess(*this, base, addr, field);
   }
 
   // If this is a reference field, load the reference right now.

diff  --git a/clang/test/CodeGen/builtin-preserve-access-index-typedef.c b/clang/test/CodeGen/builtin-preserve-access-index-typedef.c
new file mode 100644
index 000000000000..c7752cd23abd
--- /dev/null
+++ b/clang/test/CodeGen/builtin-preserve-access-index-typedef.c
@@ -0,0 +1,24 @@
+// REQUIRES: bpf-registered-target
+// RUN: %clang -target bpf -emit-llvm -S -g %s -o - | FileCheck %s
+
+#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
+typedef struct {
+   int a;
+} __t;
+typedef union {
+   int b;
+} __u;
+#pragma clang attribute pop
+
+int test1(__t *arg) { return arg->a; }
+int test2(const __u *arg) { return arg->b; }
+
+
+// CHECK: define dso_local i32 @test1
+// CHECK: call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.__ts(%struct.__t* %{{[0-9a-z]+}}, i32 0, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[TYPEDEF_STRUCT:[0-9]+]]
+// CHECK: define dso_local i32 @test2
+// CHECK: call %union.__u* @llvm.preserve.union.access.index.p0s_union.__us.p0s_union.__us(%union.__u* %{{[0-9a-z]+}}, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[CONST_TYPEDEF:[0-9]+]]
+//
+// CHECK: ![[TYPEDEF_STRUCT]] = !DIDerivedType(tag: DW_TAG_typedef, name: "__t"
+// CHECK: ![[CONST_TYPEDEF]] = !DIDerivedType(tag: DW_TAG_const_type, baseType: ![[TYPEDEF_UNION:[0-9]+]]
+// CHECK: ![[TYPEDEF_UNION]] = !DIDerivedType(tag: DW_TAG_typedef, name: "__u"