[PATCH] D34135: [JumpThreading] Use DT to avoid processing dead blocks

[Brian Rzycki via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL327432: [LazyValueInfo] PR33357 prevent infinite recursion on BinaryOperator (authored by brzycki, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D34135?vs=130139&id=138235#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D34135

Files:
  llvm/trunk/lib/Analysis/LazyValueInfo.cpp
  llvm/trunk/test/Transforms/JumpThreading/PR33357-lvi-recursion.ll


Index: llvm/trunk/lib/Analysis/LazyValueInfo.cpp
===================================================================
--- llvm/trunk/lib/Analysis/LazyValueInfo.cpp
+++ llvm/trunk/lib/Analysis/LazyValueInfo.cpp
@@ -1145,9 +1145,17 @@
              (!isTrueDest && BO->getOpcode() != BinaryOperator::Or))
     return ValueLatticeElement::getOverdefined();
 
-  auto RHS = getValueFromCondition(Val, BO->getOperand(0), isTrueDest, Visited);
-  auto LHS = getValueFromCondition(Val, BO->getOperand(1), isTrueDest, Visited);
-  return intersect(RHS, LHS);
+  // Prevent infinite recursion if Cond references itself as in this example:
+  //  Cond: "%tmp4 = and i1 %tmp4, undef"
+  //    BL: "%tmp4 = and i1 %tmp4, undef"
+  //    BR: "i1 undef"
+  Value *BL = BO->getOperand(0);
+  Value *BR = BO->getOperand(1);
+  if (BL == Cond || BR == Cond)
+    return ValueLatticeElement::getOverdefined();
+
+  return intersect(getValueFromCondition(Val, BL, isTrueDest, Visited),
+                   getValueFromCondition(Val, BR, isTrueDest, Visited));
 }
 
 static ValueLatticeElement
Index: llvm/trunk/test/Transforms/JumpThreading/PR33357-lvi-recursion.ll
===================================================================
--- llvm/trunk/test/Transforms/JumpThreading/PR33357-lvi-recursion.ll
+++ llvm/trunk/test/Transforms/JumpThreading/PR33357-lvi-recursion.ll
@@ -0,0 +1,37 @@
+; RUN: opt -S -jump-threading -verify -o - %s | FileCheck %s
+ at a = external global i16, align 1
+
+; CHECK-LABEL: f
+; CHECK: bb6:
+; CHECK: bb2:
+; CHECK: bb3:
+; CHECK-NOT: bb0:
+; CHECK-NOT: bb1:
+; CHECK-NOT: bb4:
+; CHECK-NOT: bb5:
+define void @f(i32 %p1) {
+bb0:
+  %0 = icmp eq i32 %p1, 0
+  br i1 undef, label %bb6, label %bb1
+
+bb1:
+  br label %bb2
+
+bb2:
+  %1 = phi i1 [ %0, %bb1 ], [ %2, %bb4 ]
+  %2 = and i1 %1, undef
+  br i1 %2, label %bb3, label %bb4
+
+bb3:
+  store i16 undef, i16* @a, align 1
+  br label %bb4
+
+bb4:
+  br i1 %0, label %bb2, label %bb5
+
+bb5:
+  unreachable
+
+bb6:
+  ret void
+}


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