[CGP] add helper function for generating compare of load pairs; NFCI

In the special (but also the likely common) case, we can avoid
the multi-block complexity of the general algorithm, so moving
this part off on its own will make it re-usable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304908 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CodeGenPrepare.cpp b/lib/CodeGen/CodeGenPrepare.cpp
index 3da61ca0bdcc5de05615e76e53b1e7a81fa45993..ac1e0b46fcd456c35a2548605dfae223088f7ab0 100644 (file)
--- a/lib/CodeGen/CodeGenPrepare.cpp
+++ b/lib/CodeGen/CodeGenPrepare.cpp
@@ -1668,6 +1668,8 @@ class MemCmpExpansion {
   void setupEndBlockPHINodes();
   void emitLoadCompareBlock(unsigned Index, int LoadSize, int GEPIndex,
                             bool IsLittleEndian);
+  Value *getCompareLoadPairs(unsigned Index, unsigned Size,
+                             unsigned &NumBytesProcessed, IRBuilder<> &Builder);
   void emitLoadCompareBlockMultipleLoads(unsigned Index, unsigned Size,
                                          unsigned &NumBytesProcessed);
   void emitLoadCompareByteBlock(unsigned Index, int GEPIndex);
@@ -1799,11 +1801,12 @@ unsigned MemCmpExpansion::getLoadSize(unsigned Size) {
   return MinAlign(PowerOf2Floor(Size), MaxLoadSize);
 }
 
-void MemCmpExpansion::emitLoadCompareBlockMultipleLoads(
-    unsigned Index, unsigned Size, unsigned &NumBytesProcessed) {
-
-  IRBuilder<> Builder(CI->getContext());
-
+/// Generate an equality comparison for one or more pairs of loaded values.
+/// This is used in the case where the memcmp() call is compared equal or not
+/// equal to zero.
+Value *MemCmpExpansion::getCompareLoadPairs(unsigned Index, unsigned Size,
+                                            unsigned &NumBytesProcessed,
+                                            IRBuilder<> &Builder) {
   std::vector<Value *> XorList, OrList;
   Value *Diff;
 
@@ -1880,6 +1883,14 @@ void MemCmpExpansion::emitLoadCompareBlockMultipleLoads(
     Cmp = Builder.CreateICmpNE(OrList[0], ConstantInt::get(Diff->getType(), 0));
   }
 
+  return Cmp;
+}
+
+void MemCmpExpansion::emitLoadCompareBlockMultipleLoads(
+    unsigned Index, unsigned Size, unsigned &NumBytesProcessed) {
+  IRBuilder<> Builder(CI->getContext());
+  Value *Cmp = getCompareLoadPairs(Index, Size, NumBytesProcessed, Builder);
+
   BasicBlock *NextBB = (Index == (LoadCmpBlocks.size() - 1))
                            ? EndBlock
                            : LoadCmpBlocks[Index + 1];