[BPF] annotate DIType metadata for builtin preseve_array_access_index()

Previously, debuginfo types are annotated to
IR builtin preserve_struct_access_index() and
preserve_union_access_index(), but not
preserve_array_access_index(). The debug info
is useful to identify the root type name which
later will be used for type comparison.

For user access without explicit type conversions,
the previous scheme works as we can ignore intermediate
compiler generated type conversions (e.g., from union types to
union members) and still generate correct access index string.

The issue comes with user explicit type conversions, e.g.,
converting an array to a structure like below:
  struct t { int a; char b[40]; };
  struct p { int c; int d; };
  struct t *var = ...;
  ... __builtin_preserve_access_index(&(((struct p *)&(var->b[0]))->d)) ...
Although BPF backend can derive the type of &(var->b[0]),
explicit type annotation make checking more consistent
and less error prone.

Another benefit is for multiple dimension array handling.
For example,
  struct p { int c; int d; } g[8][9][10];
  ... __builtin_preserve_access_index(&g[2][3][4].d) ...
It would be possible to calculate the number of "struct p"'s
before accessing its member "d" if array debug info is
available as it contains each dimension range.

This patch enables to annotate IR builtin preserve_array_access_index()
with proper debuginfo type. The unit test case and language reference
is updated as well.

Signed-off-by: Yonghong Song <yhs@fb.com>
Differential Revision: https://reviews.llvm.org/D65664

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@367724 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index 5fa698e75107645b834eab205f4e5b21c0a82740..a6acdeaf85e51beb86497727b34b1acc2c9562d2 100644 (file)
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -17395,6 +17395,10 @@ based on array base ``base``, array dimension ``dim`` and the last access index
 into the array. The return type ``ret_type`` is a pointer type to the array element.
 The array ``dim`` and ``index`` are preserved which is more robust than
 getelementptr instruction which may be subject to compiler transformation.
+The ``llvm.preserve.access.index`` type of metadata is attached to this call instruction
+to provide array or pointer debuginfo type.
+The metadata is a ``DICompositeType`` or ``DIDerivedType`` representing the
+debuginfo version of ``type``.
 
 Arguments:
 """"""""""

diff --git a/include/llvm/IR/IRBuilder.h b/include/llvm/IR/IRBuilder.h
index 88630f560386660d5c9d17d3f2325f57adc39759..35014ed5eceb18db0c1b797e35b134ca5ab71b3e 100644 (file)
--- a/include/llvm/IR/IRBuilder.h
+++ b/include/llvm/IR/IRBuilder.h
@@ -2484,7 +2484,7 @@ public:
   }
 
   Value *CreatePreserveArrayAccessIndex(Value *Base, unsigned Dimension,
-                                        unsigned LastIndex) {
+                                        unsigned LastIndex, MDNode *DbgInfo) {
     assert(isa<PointerType>(Base->getType()) &&
            "Invalid Base ptr type for preserve.array.access.index.");
     auto *BaseType = Base->getType();
@@ -2506,6 +2506,8 @@ public:
     Value *DimV = getInt32(Dimension);
     CallInst *Fn =
         CreateCall(FnPreserveArrayAccessIndex, {Base, DimV, LastIndexV});
+    if (DbgInfo)
+      Fn->setMetadata(LLVMContext::MD_preserve_access_index, DbgInfo);
 
     return Fn;
   }
@@ -2523,7 +2525,8 @@ public:
     Value *DIIndex = getInt32(FieldIndex);
     CallInst *Fn =
         CreateCall(FnPreserveUnionAccessIndex, {Base, DIIndex});
-    Fn->setMetadata(LLVMContext::MD_preserve_access_index, DbgInfo);
+    if (DbgInfo)
+      Fn->setMetadata(LLVMContext::MD_preserve_access_index, DbgInfo);
 
     return Fn;
   }
@@ -2546,7 +2549,8 @@ public:
     Value *DIIndex = getInt32(FieldIndex);
     CallInst *Fn = CreateCall(FnPreserveStructAccessIndex,
                               {Base, GEPIndex, DIIndex});
-    Fn->setMetadata(LLVMContext::MD_preserve_access_index, DbgInfo);
+    if (DbgInfo)
+      Fn->setMetadata(LLVMContext::MD_preserve_access_index, DbgInfo);
 
     return Fn;
   }

diff --git a/test/CodeGen/BPF/CORE/intrinsic-array.ll b/test/CodeGen/BPF/CORE/intrinsic-array.ll
index adbcb9fd75ad2a51dfe15e5c22167b13dc7d74c1..fe2c1968fd9e536a368c7edc25a39e029c0c3a08 100644 (file)
--- a/test/CodeGen/BPF/CORE/intrinsic-array.ll
+++ b/test/CodeGen/BPF/CORE/intrinsic-array.ll
@@ -14,7 +14,7 @@
 define dso_local i32 @test(%struct.s* %arg) local_unnamed_addr #0 !dbg !7 {
 entry:
   call void @llvm.dbg.value(metadata %struct.s* %arg, metadata !17, metadata !DIExpression()), !dbg !18
-  %0 = tail call %struct.s* @llvm.preserve.array.access.index.p0s_struct.ss.p0s_struct.ss(%struct.s* %arg, i32 0, i32 2), !dbg !19
+  %0 = tail call %struct.s* @llvm.preserve.array.access.index.p0s_struct.ss.p0s_struct.ss(%struct.s* %arg, i32 0, i32 2), !dbg !19, !llvm.preserve.access.index !11
   %1 = tail call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.ss(%struct.s* %0, i32 1, i32 1), !dbg !19, !llvm.preserve.access.index !12
   %2 = bitcast i32* %1 to i8*, !dbg !19
   %call = tail call i32 @get_value(i8* %2) #4, !dbg !20