From 22f5d07f74e505568fd36b81d1f37b09eda9da4b Mon Sep 17 00:00:00 2001
From: Adrian Prantl <aprantl@apple.com>
Date: Wed, 30 Aug 2017 16:49:21 +0000
Subject: [PATCH] Verifier: Verify the correctness of fragment expressions
 attached to globals.

llvm-svn: 312139
---
 lib/IR/Verifier.cpp       | 30 ++++++++++++++++++++++--------
 test/Verifier/fragment.ll | 19 +++++++++++++++++++
 2 files changed, 41 insertions(+), 8 deletions(-)
 create mode 100644 test/Verifier/fragment.ll

diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index e28644a081c..e62daeeb539 100644
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -507,6 +507,10 @@ private:
   void verifySiblingFuncletUnwinds();
 
   void verifyFragmentExpression(const DbgInfoIntrinsic &I);
+  template <typename ValueOrMetadata>
+  void verifyFragmentExpression(const DIVariable &V,
+                                DIExpression::FragmentInfo Fragment,
+                                ValueOrMetadata *Desc);
   void verifyFnArgs(const DbgInfoIntrinsic &I);
 
   /// Module-level debug info verification...
@@ -1178,8 +1182,11 @@ void Verifier::visitDIExpression(const DIExpression &N) {
 void Verifier::visitDIGlobalVariableExpression(
     const DIGlobalVariableExpression &GVE) {
   AssertDI(GVE.getVariable(), "missing variable");
-  if (auto *Expr = GVE.getExpression())
+  if (auto *Expr = GVE.getExpression()) {
     visitDIExpression(*Expr);
+    if (auto Fragment = Expr->getFragmentInfo())
+      verifyFragmentExpression(*GVE.getVariable(), *Fragment, &GVE);
+  }
 }
 
 void Verifier::visitDIObjCProperty(const DIObjCProperty &N) {
@@ -4488,7 +4495,7 @@ void Verifier::visitDbgIntrinsic(StringRef Kind, DbgIntrinsicTy &DII) {
   verifyFnArgs(DII);
 }
 
-static uint64_t getVariableSize(const DILocalVariable &V) {
+static uint64_t getVariableSize(const DIVariable &V) {
   // Be careful of broken types (checked elsewhere).
   const Metadata *RawType = V.getRawType();
   while (RawType) {
@@ -4527,7 +4534,7 @@ void Verifier::verifyFragmentExpression(const DbgInfoIntrinsic &I) {
   if (!V || !E || !E->isValid())
     return;
 
-  // Nothing to do if this isn't a bit piece expression.
+  // Nothing to do if this isn't a DW_OP_LLVM_fragment expression.
   auto Fragment = E->getFragmentInfo();
   if (!Fragment)
     return;
@@ -4541,17 +4548,24 @@ void Verifier::verifyFragmentExpression(const DbgInfoIntrinsic &I) {
   if (V->isArtificial())
     return;
 
+  verifyFragmentExpression(*V, *Fragment, &I);
+}
+
+template <typename ValueOrMetadata>
+void Verifier::verifyFragmentExpression(const DIVariable &V,
+                                        DIExpression::FragmentInfo Fragment,
+                                        ValueOrMetadata *Desc) {
   // If there's no size, the type is broken, but that should be checked
   // elsewhere.
-  uint64_t VarSize = getVariableSize(*V);
+  uint64_t VarSize = getVariableSize(V);
   if (!VarSize)
     return;
 
-  unsigned FragSize = Fragment->SizeInBits;
-  unsigned FragOffset = Fragment->OffsetInBits;
+  unsigned FragSize = Fragment.SizeInBits;
+  unsigned FragOffset = Fragment.OffsetInBits;
   AssertDI(FragSize + FragOffset <= VarSize,
-         "fragment is larger than or outside of variable", &I, V, E);
-  AssertDI(FragSize != VarSize, "fragment covers entire variable", &I, V, E);
+         "fragment is larger than or outside of variable", Desc, &V);
+  AssertDI(FragSize != VarSize, "fragment covers entire variable", Desc, &V);
 }
 
 void Verifier::verifyFnArgs(const DbgInfoIntrinsic &I) {
diff --git a/test/Verifier/fragment.ll b/test/Verifier/fragment.ll
new file mode 100644
index 00000000000..ed5df89cb31
--- /dev/null
+++ b/test/Verifier/fragment.ll
@@ -0,0 +1,19 @@
+; RUN: not opt -S <%s 2>&1| FileCheck %s
+
+; CHECK: fragment is larger than or outside of variable
+; CHECK: !DIGlobalVariableExpression(var: ![[VAR:[0-9]+]],
+; CHECK-SAME:                        expr: !DIExpression(DW_OP_LLVM_fragment, 0, 64))
+; CHECK: ![[VAR]] = !DIGlobalVariable(name: "g"
+
+@g = common global i32 0, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!1}
+!llvm.module.flags = !{!6, !7}
+
+!0 = !DIGlobalVariableExpression(var: !3, expr: !DIExpression(DW_OP_LLVM_fragment, 0, 64))
+!1 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2, emissionKind: FullDebug)
+!2 = !DIFile(filename: "a.c", directory: "/")
+!3 = !DIGlobalVariable(name: "g", scope: !1, file: !2, line: 1, type: !5, isLocal: false, isDefinition: true)
+!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!6 = !{i32 2, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}