PR12145: Avoid emitting loads of constexpr variables in contexts where there

is no odr-use of the variable. Go slightly beyond what the standard requires
for variables of reference type.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@151879 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 27 insertions, 0 deletions

diff --git a/test/CodeGenCXX/const-init-cxx11.cpp b/test/CodeGenCXX/const-init-cxx11.cpp
index 5366d6d485..776a1e12dd 100644
--- a/test/CodeGenCXX/const-init-cxx11.cpp
+++ b/test/CodeGenCXX/const-init-cxx11.cpp
@@ -337,3 +337,30 @@ namespace VirtualBase {
   X<D> x;
   // CHECK: call {{.*}}@_ZN11VirtualBase1XINS_1DEEC1Ev
 }
+
+// PR12145
+namespace Unreferenced {
+  int n;
+  constexpr int *p = &n;
+  // We must not emit a load of 'p' here, since it's not odr-used.
+  int q = *p;
+  // CHECK-NOT: _ZN12Unreferenced1pE
+  // CHECK: %0 = load i32* @_ZN12Unreferenced1nE
+  // CHECK-NEXT: store i32 %0, i32* @_ZN12Unreferenced1qE
+  // CHECK-NOT: _ZN12Unreferenced1pE
+
+  // Technically, we are not required to substitute variables of reference types
+  // initialized by constant expressions, because the special case for odr-use
+  // of variables in [basic.def.odr]p2 only applies to objects. But we do so
+  // anyway.
+
+  constexpr int &r = n;
+  // CHECK-NOT: _ZN12Unreferenced1rE
+  int s = r;
+
+  const int t = 1;
+  const int &rt = t;
+  int f(int);
+  int u = f(rt);
+  // CHECK: call i32 @_ZN12Unreferenced1fEi(i32 1)
+}