2 files changed, 118 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 0d1d34e0cb4..cdeaaa36ada 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -389,6 +389,8 @@ namespace {
                                  Value *Val, BasicBlock *BB);
     bool solveBlockValuePHINode(LVILatticeVal &BBLV,
                                 PHINode *PN, BasicBlock *BB);
+    bool solveBlockValueSelect(LVILatticeVal &BBLV,
+                               SelectInst *S, BasicBlock *BB);
     bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
                                       Instruction *BBI, BasicBlock *BB);
     void mergeAssumeBlockValueConstantRange(Value *Val, LVILatticeVal &BBLV,
@@ -587,6 +589,13 @@ bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
     return true;
   }
 
+  if (auto *SI = dyn_cast<SelectInst>(BBI)) {
+    if (!solveBlockValueSelect(Res, SI, BB))
+      return false;
+    insertResult(Val, BB, Res);
+    return true;
+  }
+
   // If this value is a nonnull pointer, record it's range and bailout.
   PointerType *PT = dyn_cast<PointerType>(BBI->getType());
   if (PT && isKnownNonNull(BBI)) {
@@ -809,6 +818,46 @@ void LazyValueInfoCache::mergeAssumeBlockValueConstantRange(Value *Val,
   }
 }
 
+bool LazyValueInfoCache::solveBlockValueSelect(LVILatticeVal &BBLV,
+                                               SelectInst *SI, BasicBlock *BB) {
+
+  // Recurse on our inputs if needed
+  if (!hasBlockValue(SI->getTrueValue(), BB)) {
+    if (pushBlockValue(std::make_pair(BB, SI->getTrueValue())))
+      return false;
+    BBLV.markOverdefined();
+    return true;
+  }
+  LVILatticeVal TrueVal = getBlockValue(SI->getTrueValue(), BB);
+  // If we hit overdefined, don't ask more queries.  We want to avoid poisoning
+  // extra slots in the table if we can.
+  if (TrueVal.isOverdefined()) {
+    BBLV.markOverdefined();
+    return true;
+  }
+
+  if (!hasBlockValue(SI->getFalseValue(), BB)) {
+    if (pushBlockValue(std::make_pair(BB, SI->getFalseValue())))
+      return false;
+    BBLV.markOverdefined();
+    return true;
+  }
+  LVILatticeVal FalseVal = getBlockValue(SI->getFalseValue(), BB);
+  // If we hit overdefined, don't ask more queries.  We want to avoid poisoning
+  // extra slots in the table if we can.
+  if (FalseVal.isOverdefined()) {
+    BBLV.markOverdefined();
+    return true;
+  }
+
+  LVILatticeVal Result;  // Start Undefined.
+  Result.mergeIn(TrueVal, DL);
+  Result.mergeIn(FalseVal, DL);
+  assert(!Result.isOverdefined() && "Should have exited previously");
+  BBLV = Result;
+  return true;
+}
+
 bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
                                                       Instruction *BBI,
                                                       BasicBlock *BB) {
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/select.ll b/llvm/test/Transforms/CorrelatedValuePropagation/select.ll
index be44bdcd921..bad8e6b74f5 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/select.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/select.ll
@@ -73,3 +73,72 @@ if.end:
   ret i32 %sel
 ; CHECK: ret i32 1
 }
+
+define i1 @test1(i32* %p, i1 %unknown) {
+; CHECK-LABEL: @test1
+  %pval = load i32, i32* %p
+  %cmp1 = icmp slt i32 %pval, 255
+  br i1 %cmp1, label %next, label %exit
+
+next:
+  %min = select i1 %unknown, i32 %pval, i32 5
+  ;; TODO: This pointless branch shouldn't be neccessary
+  br label %next2
+next2:
+; CHECK-LABEL: next2:
+; CHECK: ret i1 false
+  %res = icmp eq i32 %min, 255
+  ret i1 %res
+
+exit:
+; CHECK-LABEL: exit:
+; CHECK: ret i1 true
+  ret i1 true
+}
+
+; Check that we take a conservative meet
+define i1 @test2(i32* %p, i32 %qval, i1 %unknown) {
+; CHECK-LABEL: test2
+  %pval = load i32, i32* %p
+  %cmp1 = icmp slt i32 %pval, 255
+  br i1 %cmp1, label %next, label %exit
+
+next:
+  %min = select i1 %unknown, i32 %pval, i32 %qval
+  ;; TODO: This pointless branch shouldn't be neccessary
+  br label %next2
+next2:
+; CHECK-LABEL: next2
+; CHECK: ret i1 %res
+  %res = icmp eq i32 %min, 255
+  ret i1 %res
+
+exit:
+; CHECK-LABEL: exit:
+; CHECK: ret i1 true
+  ret i1 true
+}
+
+; Same as @test2, but for the opposite select input
+define i1 @test3(i32* %p, i32 %qval, i1 %unknown) {
+; CHECK-LABEL: test3
+  %pval = load i32, i32* %p
+  %cmp1 = icmp slt i32 %pval, 255
+  br i1 %cmp1, label %next, label %exit
+
+next:
+  %min = select i1 %unknown, i32 %qval, i32 %pval
+  ;; TODO: This pointless branch shouldn't be neccessary
+  br label %next2
+next2:
+; CHECK-LABEL: next2
+; CHECK: ret i1 %res
+  %res = icmp eq i32 %min, 255
+  ret i1 %res
+
+exit:
+; CHECK-LABEL: exit:
+; CHECK: ret i1 true
+  ret i1 true
+}
+