1 files changed, 28 insertions, 3 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index a53f2f6..ee4f97f 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Analysis/AssumeBundleQueries.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/DomConditionCache.h"
 #include "llvm/Analysis/GuardUtils.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/Loads.h"
@@ -706,9 +707,33 @@ static void computeKnownBitsFromCmp(const Value *V, CmpInst::Predicate Pred,
 
 void llvm::computeKnownBitsFromContext(const Value *V, KnownBits &Known,
                                       unsigned Depth, const SimplifyQuery &Q) {
-  // Use of assumptions is context-sensitive. If we don't have a context, we
-  // cannot use them!
-  if (!Q.AC || !Q.CxtI)
+  if (!Q.CxtI)
+    return;
+
+  if (Q.DC && Q.DT) {
+    // Handle dominating conditions.
+    for (BranchInst *BI : Q.DC->conditionsFor(V)) {
+      auto *Cmp = dyn_cast<ICmpInst>(BI->getCondition());
+      if (!Cmp)
+        continue;
+
+      BasicBlockEdge Edge0(BI->getParent(), BI->getSuccessor(0));
+      if (Q.DT->dominates(Edge0, Q.CxtI->getParent()))
+        computeKnownBitsFromCmp(V, Cmp->getPredicate(), Cmp->getOperand(0),
+                                Cmp->getOperand(1), Known, Depth, Q);
+
+      BasicBlockEdge Edge1(BI->getParent(), BI->getSuccessor(1));
+      if (Q.DT->dominates(Edge1, Q.CxtI->getParent()))
+        computeKnownBitsFromCmp(V, Cmp->getInversePredicate(),
+                                Cmp->getOperand(0), Cmp->getOperand(1), Known,
+                                Depth, Q);
+    }
+
+    if (Known.hasConflict())
+      Known.resetAll();
+  }
+
+  if (!Q.AC)
     return;
 
   unsigned BitWidth = Known.getBitWidth();