DebugInfo: Don't lose unreferenced non-trivial by-value parameters

A FastISel optimization was causing us to emit no information for such
parameters & when they go missing we end up emitting a different
function type. By avoiding that shortcut we not only get types correct
(very important) but also location information (handy) - even if it's
only live at the start of a function & may be clobbered later.

Reviewed/discussion by Evan Cheng & Dan Gohman.

llvm-svn: 184604

1 files changed, 4 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 82f9f76baba..49169b4fa3a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -97,14 +97,12 @@ bool FastISel::LowerArguments() {
   if (!FastLowerArguments())
     return false;
 
-  // Enter non-dead arguments into ValueMap for uses in non-entry BBs.
+  // Enter arguments into ValueMap for uses in non-entry BBs.
   for (Function::const_arg_iterator I = FuncInfo.Fn->arg_begin(),
          E = FuncInfo.Fn->arg_end(); I != E; ++I) {
-    if (!I->use_empty()) {
-      DenseMap<const Value *, unsigned>::iterator VI = LocalValueMap.find(I);
-      assert(VI != LocalValueMap.end() && "Missed an argument?");
-      FuncInfo.ValueMap[I] = VI->second;
-    }
+    DenseMap<const Value *, unsigned>::iterator VI = LocalValueMap.find(I);
+    assert(VI != LocalValueMap.end() && "Missed an argument?");
+    FuncInfo.ValueMap[I] = VI->second;
   }
   return true;
 }