[dwarf] Emit a DIGlobalVariable for constant strings.

An upcoming patch will extend llvm-symbolizer to provide the source line
information for global variables. The goal is to move AddressSanitizer
off of internal debug info for symbolization onto the DWARF standard
(and doing a clean-up in the process). Currently, ASan reports the line
information for constant strings if a memory safety bug happens around
them. We want to keep this behaviour, so we need to emit debuginfo for
these variables as well.

Reviewed By: dblaikie, rnk, aprantl

Differential Revision: https://reviews.llvm.org/D123534

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 83d77cb..ece4167 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -3175,6 +3175,11 @@ void CodeViewDebug::collectGlobalVariableInfo() {
     for (const auto *GVE : CU->getGlobalVariables()) {
       const DIGlobalVariable *DIGV = GVE->getVariable();
       const DIExpression *DIE = GVE->getExpression();
+      // Don't emit string literals in CodeView, as the only useful parts are
+      // generally the filename and line number, which isn't possible to output
+      // in CodeView. String literals should be the only unnamed GlobalVariable
+      // with debug info.
+      if (DIGV->getName().empty()) continue;
 
       if ((DIE->getNumElements() == 2) &&
           (DIE->getElement(0) == dwarf::DW_OP_plus_uconst))