Use TargetSubtargetInfo::useAA() in DAGCombine

This uses the TargetSubtargetInfo::useAA() function to control the defaults of
the -combiner-alias-analysis and -combiner-global-alias-analysis options.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189564 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1de11e9..144c694 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -35,6 +35,7 @@
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
 #include <algorithm>
 using namespace llvm;
 
@@ -7488,7 +7489,9 @@
     }
   }
 
-  if (CombinerAA) {
+  bool UseAA = CombinerAA.getNumOccurrences() > 0 ? CombinerAA :
+    TLI.getTargetMachine().getSubtarget<TargetSubtargetInfo>().useAA();
+  if (UseAA) {
     // Walk up chain skipping non-aliasing memory nodes.
     SDValue BetterChain = FindBetterChain(N, Chain);
 
@@ -8519,7 +8522,9 @@
   if (NewST.getNode())
     return NewST;
 
-  if (CombinerAA) {
+  bool UseAA = CombinerAA.getNumOccurrences() > 0 ? CombinerAA :
+    TLI.getTargetMachine().getSubtarget<TargetSubtargetInfo>().useAA();
+  if (UseAA) {
     // Walk up chain skipping non-aliasing memory nodes.
     SDValue BetterChain = FindBetterChain(N, Chain);
 
@@ -10229,7 +10234,9 @@
       return false;
   }
 
-  if (CombinerGlobalAA) {
+  bool UseAA = CombinerGlobalAA.getNumOccurrences() > 0 ? CombinerGlobalAA :
+    TLI.getTargetMachine().getSubtarget<TargetSubtargetInfo>().useAA();
+  if (UseAA) {
     // Use alias analysis information.
     int64_t MinOffset = std::min(SrcValueOffset1, SrcValueOffset2);
     int64_t Overlap1 = Size1 + SrcValueOffset1 - MinOffset;