Index: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
@@ -1812,7 +1812,7 @@
   unsigned NumLoads = std::min(NumLoadsRemaining, NumLoadsPerBlock);
 
   Builder.SetInsertPoint(LoadCmpBlocks[Index]);
-
+  Value *Cmp = nullptr;
   for (unsigned i = 0; i < NumLoads; ++i) {
     unsigned LoadSize = getLoadSize(RemainingBytes);
     unsigned GEPIndex = NumBytesProcessed / LoadSize;
@@ -1846,9 +1846,16 @@
       LoadSrc1 = Builder.CreateZExtOrTrunc(LoadSrc1, MaxLoadType);
       LoadSrc2 = Builder.CreateZExtOrTrunc(LoadSrc2, MaxLoadType);
     }
-    Diff = Builder.CreateXor(LoadSrc1, LoadSrc2);
-    Diff = Builder.CreateZExtOrTrunc(Diff, MaxLoadType);
-    XorList.push_back(Diff);
+    if (NumLoads != 1) {
+      // If we have multiple loads per block, we need to generate a composite
+      // comparison using xor+or.
+      Diff = Builder.CreateXor(LoadSrc1, LoadSrc2);
+      Diff = Builder.CreateZExtOrTrunc(Diff, MaxLoadType);
+      XorList.push_back(Diff);
+    } else {
+      // If there's only one load per block, we just compare the loaded values.
+      Cmp = Builder.CreateICmpNE(LoadSrc1, LoadSrc2);
+    }
   }
 
   auto pairWiseOr = [&](std::vector<Value *> &InList) -> std::vector<Value *> {
@@ -1862,16 +1869,17 @@
     return OutList;
   };
 
-  // Pairwise OR the XOR results.
-  OrList = pairWiseOr(XorList);
-
-  // Pairwise OR the OR results until one result left.
-  while (OrList.size() != 1) {
-    OrList = pairWiseOr(OrList);
+  if (!Cmp) {
+    // Pairwise OR the XOR results.
+    OrList = pairWiseOr(XorList);
+
+    // Pairwise OR the OR results until one result left.
+    while (OrList.size() != 1) {
+      OrList = pairWiseOr(OrList);
+    }
+    Cmp = Builder.CreateICmpNE(OrList[0], ConstantInt::get(Diff->getType(), 0));
   }
 
-  Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_NE, OrList[0],
-                                  ConstantInt::get(Diff->getType(), 0));
   BasicBlock *NextBB = (Index == (LoadCmpBlocks.size() - 1))
                            ? EndBlock
                            : LoadCmpBlocks[Index + 1];
Index: llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
===================================================================
--- llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
+++ llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
@@ -21,8 +21,7 @@
 ; CHECK-NEXT:    lwz 3, 0(3)
 ; CHECK-NEXT:    lwz 4, 0(4)
 ; CHECK-NEXT:    li 5, 1
-; CHECK-NEXT:    xor 3, 3, 4
-; CHECK-NEXT:    cmplwi 3, 0
+; CHECK-NEXT:    cmpld 3, 4
 ; CHECK-NEXT:    isel 3, 0, 5, 2
 ; CHECK-NEXT:    clrldi 3, 3, 32
 ; CHECK-NEXT:    blr
@@ -38,19 +37,19 @@
 ; CHECK:       # BB#0: # %loadbb
 ; CHECK-NEXT:    ld 5, 0(3)
 ; CHECK-NEXT:    ld 6, 0(4)
-; CHECK-NEXT:    xor. 5, 5, 6
+; CHECK-NEXT:    cmpld 5, 6
 ; CHECK-NEXT:    bne 0, .LBB1_2
 ; CHECK-NEXT:  # BB#1: # %loadbb1
 ; CHECK-NEXT:    ld 3, 8(3)
 ; CHECK-NEXT:    ld 4, 8(4)
-; CHECK-NEXT:    xor. 3, 3, 4
+; CHECK-NEXT:    cmpld 3, 4
+; CHECK-NEXT:    li 3, 0
 ; CHECK-NEXT:    beq 0, .LBB1_3
 ; CHECK-NEXT:  .LBB1_2: # %res_block
 ; CHECK-NEXT:    li 3, 1
 ; CHECK-NEXT:    clrldi 3, 3, 32
 ; CHECK-NEXT:    blr
-; CHECK-NEXT:  .LBB1_3:
-; CHECK-NEXT:    li 3, 0
+; CHECK-NEXT:  .LBB1_3: # %endblock
 ; CHECK-NEXT:    clrldi 3, 3, 32
 ; CHECK-NEXT:    blr
   %call = tail call signext i32 @memcmp(i8* %x, i8* %y, i64 16)
@@ -65,27 +64,24 @@
 ; CHECK:       # BB#0: # %loadbb
 ; CHECK-NEXT:    lwz 5, 0(3)
 ; CHECK-NEXT:    lwz 6, 0(4)
-; CHECK-NEXT:    xor 5, 5, 6
-; CHECK-NEXT:    cmplwi 5, 0
+; CHECK-NEXT:    cmpld 5, 6
 ; CHECK-NEXT:    bne 0, .LBB2_3
 ; CHECK-NEXT:  # BB#1: # %loadbb1
 ; CHECK-NEXT:    lhz 5, 4(3)
 ; CHECK-NEXT:    lhz 6, 4(4)
-; CHECK-NEXT:    xor 5, 5, 6
-; CHECK-NEXT:    rlwinm. 5, 5, 0, 16, 31
+; CHECK-NEXT:    cmpld 5, 6
 ; CHECK-NEXT:    bne 0, .LBB2_3
 ; CHECK-NEXT:  # BB#2: # %loadbb2
 ; CHECK-NEXT:    lbz 3, 6(3)
 ; CHECK-NEXT:    lbz 4, 6(4)
-; CHECK-NEXT:    xor 3, 3, 4
-; CHECK-NEXT:    rlwinm. 3, 3, 0, 24, 31
+; CHECK-NEXT:    cmpld 3, 4
+; CHECK-NEXT:    li 3, 0
 ; CHECK-NEXT:    beq 0, .LBB2_4
 ; CHECK-NEXT:  .LBB2_3: # %res_block
 ; CHECK-NEXT:    li 3, 1
 ; CHECK-NEXT:    clrldi 3, 3, 32
 ; CHECK-NEXT:    blr
-; CHECK-NEXT:  .LBB2_4:
-; CHECK-NEXT:    li 3, 0
+; CHECK-NEXT:  .LBB2_4: # %endblock
 ; CHECK-NEXT:    clrldi 3, 3, 32
 ; CHECK-NEXT:    blr
   %call = tail call signext i32 @memcmp(i8* %x, i8* %y, i64 7)
@@ -178,24 +174,22 @@
 ; CHECK-NEXT:    addis 4, 2, .LzeroEqualityTest04.buffer2@toc@ha
 ; CHECK-NEXT:    ld 3, .LzeroEqualityTest04.buffer1@toc@l(3)
 ; CHECK-NEXT:    ld 4, .LzeroEqualityTest04.buffer2@toc@l(4)
-; CHECK-NEXT:    xor. 3, 3, 4
+; CHECK-NEXT:    cmpld 3, 4
 ; CHECK-NEXT:    bne 0, .LBB5_2
 ; CHECK-NEXT:  # BB#1: # %loadbb1
 ; CHECK-NEXT:    addis 3, 2, .LzeroEqualityTest04.buffer1@toc@ha+8
 ; CHECK-NEXT:    addis 4, 2, .LzeroEqualityTest04.buffer2@toc@ha+8
 ; CHECK-NEXT:    ld 3, .LzeroEqualityTest04.buffer1@toc@l+8(3)
 ; CHECK-NEXT:    ld 4, .LzeroEqualityTest04.buffer2@toc@l+8(4)
-; CHECK-NEXT:    xor. 3, 3, 4
-; CHECK-NEXT:    beq 0, .LBB5_4
+; CHECK-NEXT:    cmpld 3, 4
+; CHECK-NEXT:    li 3, 0
+; CHECK-NEXT:    beq 0, .LBB5_3
 ; CHECK-NEXT:  .LBB5_2: # %res_block
 ; CHECK-NEXT:    li 3, 1
 ; CHECK-NEXT:  .LBB5_3: # %endblock
 ; CHECK-NEXT:    cntlzw 3, 3
 ; CHECK-NEXT:    srwi 3, 3, 5
 ; CHECK-NEXT:    blr
-; CHECK-NEXT:  .LBB5_4:
-; CHECK-NEXT:    li 3, 0
-; CHECK-NEXT:    b .LBB5_3
   %call = tail call signext i32 @memcmp(i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer1 to i8*), i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer2 to i8*), i64 16)
   %not.tobool = icmp eq i32 %call, 0
   %cond = zext i1 %not.tobool to i32