[PATCH] D32745: Correct debug info bit offset calculation for big-endian targets

[Frej Drejhammar via Phabricator via cfe-commits]

frej updated this revision to Diff 97773.
frej added a comment.

Removed 'REQUIRES'-line.


https://reviews.llvm.org/D32745

Files:
  clang/lib/CodeGen/CGDebugInfo.cpp
  clang/test/CodeGen/mips-debug-info-bitfield.c


Index: clang/test/CodeGen/mips-debug-info-bitfield.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/mips-debug-info-bitfield.c
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -x c -debug-info-kind=limited -triple mips-none-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+struct fields
+{
+  unsigned a : 4;
+  unsigned b : 4;
+} flags;
+
+// CHECK: !DIDerivedType(tag: DW_TAG_member,
+// CHECK-SAME: {{.*}}name: "a"
+// CHECK-NOT: {{.*}}offset:
+// CHECK-SAME: {{.*}}flags: DIFlagBitField
+
+// CHECK: !DIDerivedType(tag: DW_TAG_member,
+// CHECK-SAME: {{.*}}name: "b"
+// CHECK-SAME: {{.*}}offset: 4
+// CHECK-SAME: {{.*}}flags: DIFlagBitField
Index: clang/lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- clang/lib/CodeGen/CGDebugInfo.cpp
+++ clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1041,7 +1041,13 @@
   assert(SizeInBits > 0 && "found named 0-width bitfield");
   uint64_t StorageOffsetInBits =
       CGM.getContext().toBits(BitFieldInfo.StorageOffset);
-  uint64_t OffsetInBits = StorageOffsetInBits + BitFieldInfo.Offset;
+  uint64_t Offset = BitFieldInfo.Offset;
+  // The bit offsets for big endian machines are reversed for big
+  // endian target, compensate for that as the DIDerivedType requires
+  // un-reversed offsets.
+  if (CGM.getDataLayout().isBigEndian())
+    Offset = BitFieldInfo.StorageSize - BitFieldInfo.Size - Offset;
+  uint64_t OffsetInBits = StorageOffsetInBits + Offset;
   llvm::DINode::DIFlags Flags = getAccessFlag(BitFieldDecl->getAccess(), RD);
   return DBuilder.createBitFieldMemberType(
       RecordTy, Name, File, Line, SizeInBits, OffsetInBits, StorageOffsetInBits,


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