If known DebugLocs do not match then two DBG_VALUE machine instructions are not identical. For example,

        DBG_VALUE 3.310000e+02, 0, !"ds"; dbg:sse.stepfft.c:138:18 @[ sse.stepfft.c:32:10 ]
        DBG_VALUE 3.310000e+02, 0, !"ds"; dbg:sse.stepfft.c:138:18 @[ sse.stepfft.c:31:10 ]

These two MIs represent identical value, 3.31...,  for one variable, ds, but they are not identical because the represent two separate instances of inlined variable "ds". 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134620 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index f490713..143a29b 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -802,6 +802,11 @@
         return false;
     }
   }
+  // If DebugLoc does not match then two dbg.values are not identical.
+  if (isDebugValue())
+    if (!getDebugLoc().isUnknown() && !Other->getDebugLoc().isUnknown()
+        && getDebugLoc() != Other->getDebugLoc())
+      return false;
   return true;
 }