1 files changed, 22 insertions, 7 deletions
diff --git a/contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp b/contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
index 20c7d771bfb6..6d8252046501 100644
--- a/contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
+++ b/contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
@@ -14,6 +14,7 @@
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/SelectionDAGNodes.h"
 #include "llvm/CodeGen/TargetLowering.h"
+#include "llvm/IR/GlobalAlias.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"
 #include <cstdint>
@@ -143,13 +144,27 @@ bool BaseIndexOffset::computeAliasing(const SDNode *Op0,
   bool IsCV0 = isa<ConstantPoolSDNode>(BasePtr0.getBase());
   bool IsCV1 = isa<ConstantPoolSDNode>(BasePtr1.getBase());
 
-  // If of mismatched base types or checkable indices we can check
-  // they do not alias.
-  if ((BasePtr0.getIndex() == BasePtr1.getIndex() || (IsFI0 != IsFI1) ||
-       (IsGV0 != IsGV1) || (IsCV0 != IsCV1)) &&
-      (IsFI0 || IsGV0 || IsCV0) && (IsFI1 || IsGV1 || IsCV1)) {
-    IsAlias = false;
-    return true;
+  if ((IsFI0 || IsGV0 || IsCV0) && (IsFI1 || IsGV1 || IsCV1)) {
+    // We can derive NoAlias In case of mismatched base types.
+    if (IsFI0 != IsFI1 || IsGV0 != IsGV1 || IsCV0 != IsCV1) {
+      IsAlias = false;
+      return true;
+    }
+    if (IsGV0 && IsGV1) {
+      auto *GV0 = cast<GlobalAddressSDNode>(BasePtr0.getBase())->getGlobal();
+      auto *GV1 = cast<GlobalAddressSDNode>(BasePtr1.getBase())->getGlobal();
+      // It doesn't make sense to access one global value using another globals
+      // values address, so we can assume that there is no aliasing in case of
+      // two different globals (unless we have symbols that may indirectly point
+      // to each other).
+      // FIXME: This is perhaps a bit too defensive. We could try to follow the
+      // chain with aliasee information for GlobalAlias variables to find out if
+      // we indirect symbols may alias or not.
+      if (GV0 != GV1 && !isa<GlobalAlias>(GV0) && !isa<GlobalAlias>(GV1)) {
+        IsAlias = false;
+        return true;
+      }
+    }
   }
   return false; // Cannot determine whether the pointers alias.
 }