[MachineCopyPropagation] Fix a bug causing incorrect removal for the instruction sequences as follows

   %Q5_Q6<def> = COPY %Q2_Q3
   %D5<def> =
   %D3<def> =
   %D3<def> = COPY %D6     // Incorrectly removed in MachineCopyPropagation
   Using of %D3 results in incorrect result ...

   Reviewed in http://reviews.llvm.org/D8242 

llvm-svn: 232142

1 files changed, 3 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
index cbd62728ace..96111225db5 100644
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -75,10 +75,9 @@ MachineCopyPropagation::SourceNoLongerAvailable(unsigned Reg,
            I != E; ++I) {
         unsigned MappedDef = *I;
         // Source of copy is no longer available for propagation.
-        if (AvailCopyMap.erase(MappedDef)) {
-          for (MCSubRegIterator SR(MappedDef, TRI); SR.isValid(); ++SR)
-            AvailCopyMap.erase(*SR);
-        }
+        AvailCopyMap.erase(MappedDef);
+        for (MCSubRegIterator SR(MappedDef, TRI); SR.isValid(); ++SR)
+          AvailCopyMap.erase(*SR);
       }
     }
   }