DebugInfo: Avoid emitting constnants for every use

While the folding set would deduplicate the nodes themselves and LLVM
would handle not emitting the same global twice, it still meant creating
a long/redundant list of global variables.

llvm-svn: 205668

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 41f1ddb..7275e73 100644 (file)
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -3230,10 +3230,14 @@ void CGDebugInfo::EmitGlobalVariable(const ValueDecl *VD,
   // Do not emit separate definitions for function local const/statics.
   if (isa<FunctionDecl>(VD->getDeclContext()))
     return;
+  VD = cast<ValueDecl>(VD->getCanonicalDecl());
+  auto pair = DeclCache.insert(std::make_pair(VD, llvm::WeakVH()));
+  if (!pair.second)
+    return;
   llvm::DIGlobalVariable GV = DBuilder.createStaticVariable(
       Unit, Name, Name, Unit, getLineNumber(VD->getLocation()), Ty, true, Init,
       getOrCreateStaticDataMemberDeclarationOrNull(cast<VarDecl>(VD)));
-  DeclCache.insert(std::make_pair(VD->getCanonicalDecl(), llvm::WeakVH(GV)));
+  pair.first->second = llvm::WeakVH(GV);
 }
 
 llvm::DIScope CGDebugInfo::getCurrentContextDescriptor(const Decl *D) {

diff --git a/clang/test/CodeGenCXX/debug-info-global.cpp b/clang/test/CodeGenCXX/debug-info-global.cpp
new file mode 100644 (file)
index 0000000..5f075b9
--- /dev/null
+++ b/clang/test/CodeGenCXX/debug-info-global.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple x86_64-none-linux-gnu -emit-llvm -g %s -o - | FileCheck %s
+
+// Multiple references to the same constant should result in only one entry in
+// the globals list.
+
+const int cnst = 42;
+int f1() {
+  return cnst + cnst;
+}
+
+// CHECK: metadata [[GLOBALS:![0-9]*]], metadata {{![0-9]*}}, metadata !"{{.*}}", i32 {{[0-9]*}}} ; [ DW_TAG_compile_unit ]
+
+// CHECK: [[GLOBALS]] = metadata !{metadata [[CNST:![0-9]*]]}
+