Fix two issues that Eli Friedman pointed out, where would misoptimized code like:

char a[200];
init(a, a+200);

OR

int a[200];
char* b = (char*)a;
char* c = (char*)a;
foo(b, c);


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51850 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 3 deletions

diff --git a/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index c599928d82..18f5f0c130 100644
--- a/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -554,10 +554,17 @@ bool MemCpyOpt::performCallSlotOptzn(MemCpyInst *cpy, CallInst *C) {
     User* UI = srcUseList.back();
     srcUseList.pop_back();
 
-    if (isa<GetElementPtrInst>(UI) || isa<BitCastInst>(UI)) {
+    if (isa<BitCastInst>(UI)) {
       for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
            I != E; ++I)
         srcUseList.push_back(*I);
+    } else if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(UI)) {
+      if (G->hasAllZeroIndices())
+        for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
+             I != E; ++I)
+          srcUseList.push_back(*I);
+      else
+        return false;
     } else if (UI != C && UI != cpy) {
       return false;
     }
@@ -582,12 +589,16 @@ bool MemCpyOpt::performCallSlotOptzn(MemCpyInst *cpy, CallInst *C) {
   // All the checks have passed, so do the transformation.
   bool changedArgument = false;
   for (unsigned i = 0; i < CS.arg_size(); ++i)
-    if (CS.getArgument(i) == cpySrc) {
+    if (CS.getArgument(i)->stripPointerCasts() == cpySrc) {
       if (cpySrc->getType() != cpyDest->getType())
         cpyDest = CastInst::CreatePointerCast(cpyDest, cpySrc->getType(),
                                               cpyDest->getName(), C);
       changedArgument = true;
-      CS.setArgument(i, cpyDest);
+      if (CS.getArgument(i)->getType() != cpyDest->getType())
+        CS.setArgument(i, CastInst::CreatePointerCast(cpyDest, 
+                       CS.getArgument(i)->getType(), cpyDest->getName(), C));
+      else
+        CS.setArgument(i, cpyDest);
     }
 
   if (!changedArgument)