commit e2cbd13e5634e16301cd9e4b88b5ea08accafe9f
author Chad Rosier <mcrosier@codeaurora.org> Mon Apr 25 17:23:36 2016 +0000
committer Chad Rosier <mcrosier@codeaurora.org> Mon Apr 25 17:23:36 2016 +0000
tree 21cf5562f959fc1476cb2b129c884fb939e74267
parent 8d728fccb8266004f23485a9b336825d2fa79fd8

[ValueTracking] Improve isImpliedCondition when the dominating cond is false.

llvm-svn: 267430

llvm/lib/Transforms/Scalar/JumpThreading.cpp

diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index ba406a8..75c340f 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -925,11 +925,14 @@
 
   while (CurrentPred && Iter++ < ImplicationSearchThreshold) {
     auto *PBI = dyn_cast<BranchInst>(CurrentPred->getTerminator());
-    if (!PBI || !PBI->isConditional() || PBI->getSuccessor(0) != CurrentBB)
+    if (!PBI || !PBI->isConditional())
+      return false;
+    if (PBI->getSuccessor(0) != CurrentBB && PBI->getSuccessor(1) != CurrentBB)
       return false;
 
+    bool FalseDest = PBI->getSuccessor(1) == CurrentBB;
     Optional<bool> Implication =
-        isImpliedCondition(PBI->getCondition(), Cond, DL);
+      isImpliedCondition(PBI->getCondition(), Cond, DL, FalseDest);
     if (Implication) {
       BI->getSuccessor(*Implication ? 1 : 0)->removePredecessor(BB);
       BranchInst::Create(BI->getSuccessor(*Implication ? 0 : 1), BI);

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 53bea21..23199b3 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2703,11 +2703,13 @@
 
   // If BI is reached from the true path of PBI and PBI's condition implies
   // BI's condition, we know the direction of the BI branch.
-  if (PBI->getSuccessor(0) == BI->getParent() &&
+  if ((PBI->getSuccessor(0) == BI->getParent() ||
+       PBI->getSuccessor(1) == BI->getParent()) &&
       PBI->getSuccessor(0) != PBI->getSuccessor(1) &&
       BB->getSinglePredecessor()) {
-    Optional<bool> Implication =
-        isImpliedCondition(PBI->getCondition(), BI->getCondition(), DL);
+    bool FalseDest = PBI->getSuccessor(1) == BI->getParent();
+    Optional<bool> Implication = isImpliedCondition(
+        PBI->getCondition(), BI->getCondition(), DL, FalseDest);
     if (Implication) {
       // Turn this into a branch on constant.
       auto *OldCond = BI->getCondition();