[DebugInfo] Disallow fragmenting DIExpressions with shift operators

DIExpressions with shift operators should not be fragmented for the same
reason as arithmetic operators: carry over cannot be expressed from one
fragment to the other, so an invalid result would be produced.

Differential Revision: https://reviews.llvm.org/D70601

2 files changed, 49 insertions, 2 deletions

diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index e4036ee1eb0..b0102275b36 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -1148,10 +1148,14 @@ Optional<DIExpression *> DIExpression::createFragmentExpression(
     for (auto Op : Expr->expr_ops()) {
       switch (Op.getOp()) {
       default: break;
+      case dwarf::DW_OP_shr:
+      case dwarf::DW_OP_shra:
+      case dwarf::DW_OP_shl:
       case dwarf::DW_OP_plus:
+      case dwarf::DW_OP_plus_uconst:
       case dwarf::DW_OP_minus:
-        // We can't safely split arithmetic into multiple fragments because we
-        // can't express carry-over between fragments.
+        // We can't safely split arithmetic or shift operations into multiple
+        // fragments because we can't express carry-over between fragments.
         //
         // FIXME: We *could* preserve the lowest fragment of a constant offset
         // operation if the offset fits into SizeInBits.
diff --git a/llvm/unittests/IR/MetadataTest.cpp b/llvm/unittests/IR/MetadataTest.cpp
index e6c7a501139..99295681ec8 100644
--- a/llvm/unittests/IR/MetadataTest.cpp
+++ b/llvm/unittests/IR/MetadataTest.cpp
@@ -2394,6 +2394,49 @@ TEST_F(DIExpressionTest, isValid) {
 #undef EXPECT_INVALID
 }
 
+TEST_F(DIExpressionTest, createFragmentExpression) {
+#define EXPECT_VALID_FRAGMENT(Offset, Size, ...)                               \
+  do {                                                                         \
+    uint64_t Elements[] = {__VA_ARGS__};                                       \
+    DIExpression* Expression = DIExpression::get(Context, Elements);           \
+    EXPECT_TRUE(DIExpression::createFragmentExpression(                        \
+      Expression, Offset, Size).hasValue());                                   \
+  } while (false)
+#define EXPECT_INVALID_FRAGMENT(Offset, Size, ...)                             \
+  do {                                                                         \
+    uint64_t Elements[] = {__VA_ARGS__};                                       \
+    DIExpression* Expression = DIExpression::get(Context, Elements);           \
+    EXPECT_FALSE(DIExpression::createFragmentExpression(                       \
+      Expression, Offset, Size).hasValue());                                   \
+  } while (false)
+
+  // createFragmentExpression adds correct ops.
+  Optional<DIExpression*> R = DIExpression::createFragmentExpression(
+    DIExpression::get(Context, {}), 0, 32);
+  EXPECT_EQ(R.hasValue(), true);
+  EXPECT_EQ(3u, (*R)->getNumElements());
+  EXPECT_EQ(dwarf::DW_OP_LLVM_fragment, (*R)->getElement(0));
+  EXPECT_EQ(0u, (*R)->getElement(1));
+  EXPECT_EQ(32u, (*R)->getElement(2));
+
+  // Valid fragment expressions.
+  EXPECT_VALID_FRAGMENT(0, 32, {});
+  EXPECT_VALID_FRAGMENT(0, 32, dwarf::DW_OP_deref);
+  EXPECT_VALID_FRAGMENT(0, 32, dwarf::DW_OP_LLVM_fragment, 0, 32);
+  EXPECT_VALID_FRAGMENT(16, 16, dwarf::DW_OP_LLVM_fragment, 0, 32);
+
+  // Invalid fragment expressions (incompatible ops).
+  EXPECT_INVALID_FRAGMENT(0, 32, dwarf::DW_OP_constu, 6, dwarf::DW_OP_plus);
+  EXPECT_INVALID_FRAGMENT(0, 32, dwarf::DW_OP_constu, 14, dwarf::DW_OP_minus);
+  EXPECT_INVALID_FRAGMENT(0, 32, dwarf::DW_OP_constu, 16, dwarf::DW_OP_shr);
+  EXPECT_INVALID_FRAGMENT(0, 32, dwarf::DW_OP_constu, 16, dwarf::DW_OP_shl);
+  EXPECT_INVALID_FRAGMENT(0, 32, dwarf::DW_OP_constu, 16, dwarf::DW_OP_shra);
+  EXPECT_INVALID_FRAGMENT(0, 32, dwarf::DW_OP_plus_uconst, 6);
+
+#undef EXPECT_VALID_FRAGMENT
+#undef EXPECT_INVALID_FRAGMENT
+}
+
 typedef MetadataTest DIObjCPropertyTest;
 
 TEST_F(DIObjCPropertyTest, get) {