enhance the "alloca is just a memcpy from constant global"

to ignore calls that obviously can't modify the alloca
because they are readonly/readnone.

llvm-svn: 119683

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 6f4f17e20fb..fe40bcc22d5 100644
--- a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -34,6 +34,7 @@
 #include "llvm/Target/TargetData.h"
 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
 #include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Support/CallSite.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/GetElementPtrTypeIterator.h"
@@ -1810,6 +1811,12 @@ static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
       continue;
     }
     
+    // If this is a readonly/readnone call site, then we know it is just a load
+    // and we can ignore it.
+    if (CallSite CS = U)
+      if (CS.onlyReadsMemory())
+        continue;
+    
     // If this is isn't our memcpy/memmove, reject it as something we can't
     // handle.
     MemTransferInst *MI = dyn_cast<MemTransferInst>(U);