DebugInfo+DFSan: Ensure that debug info references to llvm::Functions remain pointing to the underlying function when wrappers are created

This is somewhat the inverse of how similar bugs in DAE and ArgPromo
manifested and were addressed. In those passes, individual call sites
were visited explicitly, and then the old function was deleted. This
left the debug info with a null llvm::Function* that needed to be
updated to point to the new function.

In the case of DFSan, it RAUWs the old function with the wrapper, which
includes debug info. So now the debug info refers to the wrapper, which
doesn't actually have any instructions with debug info in it, so it is
ignored entirely - resulting in a DW_TAG_subprogram with no high/low pc,
etc. Instead, fix up the debug info to refer to the original function
after the RAUW messed it up.

Reviewed/discussed with Peter Collingbourne on the llvm-dev mailing
list.

llvm-svn: 219249

3 files changed, 48 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
index 446bcf79b55..cb84fd67266 100644
--- a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -51,6 +51,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/Dominators.h"
+#include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/InstVisitor.h"
@@ -243,6 +244,7 @@ class DataFlowSanitizer : public ModulePass {
   DFSanABIList ABIList;
   DenseMap<Value *, Function *> UnwrappedFnMap;
   AttributeSet ReadOnlyNoneAttrs;
+  DenseMap<const Function *, DISubprogram> FunctionDIs;
 
   Value *getShadowAddress(Value *Addr, Instruction *Pos);
   bool isInstrumented(const Function *F);
@@ -573,6 +575,8 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
   if (ABIList.isIn(M, "skip"))
     return false;
 
+  FunctionDIs = makeSubprogramMap(M);
+
   if (!GetArgTLSPtr) {
     Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
     ArgTLS = Mod->getOrInsertGlobal("__dfsan_arg_tls", ArgTLSTy);
@@ -725,6 +729,12 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
       Value *WrappedFnCst =
           ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT));
       F.replaceAllUsesWith(WrappedFnCst);
+
+      // Patch the pointer to LLVM function in debug info descriptor.
+      auto DI = FunctionDIs.find(&F);
+      if (DI != FunctionDIs.end())
+        DI->second.replaceFunction(&F);
+
       UnwrappedFnMap[WrappedFnCst] = &F;
       *i = NewF;
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/Inputs/debuglist.txt b/llvm/test/Instrumentation/DataFlowSanitizer/Inputs/debuglist.txt
new file mode 100644
index 00000000000..daf7b5f4377
--- /dev/null
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/Inputs/debuglist.txt
@@ -0,0 +1,2 @@
+fun:main=uninstrumented
+fun:main=discard
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/debug.ll b/llvm/test/Instrumentation/DataFlowSanitizer/debug.ll
new file mode 100644
index 00000000000..cfc9dd9992a
--- /dev/null
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/debug.ll
@@ -0,0 +1,36 @@
+; RUN: opt < %s -dfsan -dfsan-abilist=%S/Inputs/debuglist.txt -S | FileCheck %s
+
+; CHECK: i32 ()* @main, {{.*}} ; [ DW_TAG_subprogram ] {{.*}} [main]
+
+; Generated from a simple source file compiled with clang -g:
+; int main() {
+; }
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: nounwind uwtable
+define i32 @main() #0 {
+entry:
+  ret i32 0, !dbg !12
+}
+
+attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = metadata !{metadata !"0x11\004\00clang version 3.6.0 \000\00\000\00\001", metadata !1, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2} ; [ DW_TAG_compile_unit ] [/tmp/dbginfo/debug.cpp] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !"debug.cpp", metadata !"/tmp/dbginfo"}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{metadata !"0x2e\00main\00main\00\001\000\001\000\000\00256\000\001", metadata !1, metadata !5, metadata !6, null, i32 ()* @main, null, null, metadata !2} ; [ DW_TAG_subprogram ] [line 1] [def] [main]
+!5 = metadata !{metadata !"0x29", metadata !1}    ; [ DW_TAG_file_type ] [/tmp/dbginfo/debug.cpp]
+!6 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null, null, null, metadata !7, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{metadata !8}
+!8 = metadata !{metadata !"0x24\00int\000\0032\0032\000\000\005", null, null} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!10 = metadata !{i32 2, metadata !"Debug Info Version", i32 2}
+!11 = metadata !{metadata !"clang version 3.6.0 "}
+!12 = metadata !{i32 2, i32 1, metadata !4, null}