From: Craig Topper <craig.topper@gmail.com>
Date: Fri, 21 Apr 2017 15:53:42 +0000 (+0000)
Subject: [SimplifyCFG] Fix the determination of PostBB in conditional store merging to handle... 
X-Git-Tag: android-x86-7.1-r4~17357
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=4f4553914f61a7366e121ecb5f7087bb462f35f2;p=android-x86%2Fexternal-llvm.git

[SimplifyCFG] Fix the determination of PostBB in conditional store merging to handle the targets on the second branch being commuted

Currently we choose PostBB as the single successor of QFB, but its possible that QTB's single successor is QFB which would make QFB the correct choice.

Differential Revision: https://reviews.llvm.org/D32323

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300992 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 2f575b9d502..e625766477d 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -3055,6 +3055,15 @@ static bool mergeConditionalStores(BranchInst *PBI, BranchInst *QBI) {
   BasicBlock *QFB = QBI->getSuccessor(1);
   BasicBlock *PostBB = QFB->getSingleSuccessor();
 
+  // Make sure we have a good guess for PostBB. If QTB's only successor is
+  // QFB, then QFB is a better PostBB.
+  if (QTB->getSingleSuccessor() == QFB)
+    PostBB = QFB;
+
+  // If we couldn't find a good PostBB, stop.
+  if (!PostBB)
+    return false;
+
   bool InvertPCond = false, InvertQCond = false;
   // Canonicalize fallthroughs to the true branches.
   if (PFB == QBI->getParent()) {
@@ -3079,8 +3088,7 @@ static bool mergeConditionalStores(BranchInst *PBI, BranchInst *QBI) {
   auto HasOnePredAndOneSucc = [](BasicBlock *BB, BasicBlock *P, BasicBlock *S) {
     return BB->getSinglePredecessor() == P && BB->getSingleSuccessor() == S;
   };
-  if (!PostBB ||
-      !HasOnePredAndOneSucc(PFB, PBI->getParent(), QBI->getParent()) ||
+  if (!HasOnePredAndOneSucc(PFB, PBI->getParent(), QBI->getParent()) ||
       !HasOnePredAndOneSucc(QFB, QBI->getParent(), PostBB))
     return false;
   if ((PTB && !HasOnePredAndOneSucc(PTB, PBI->getParent(), QBI->getParent())) ||
diff --git a/test/Transforms/SimplifyCFG/merge-cond-stores.ll b/test/Transforms/SimplifyCFG/merge-cond-stores.ll
index 0174abf2b06..a4bda96e22a 100644
--- a/test/Transforms/SimplifyCFG/merge-cond-stores.ll
+++ b/test/Transforms/SimplifyCFG/merge-cond-stores.ll
@@ -37,23 +37,17 @@ end:
 }
 
 ; This is the same as test_simple, but the branch target order has been swapped
-; TODO: This test should succeed and end up if-converted.
 define void @test_simple_commuted(i32* %p, i32 %a, i32 %b) {
 ; CHECK-LABEL: @test_simple_commuted(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[X1:%.*]] = icmp eq i32 [[A:%.*]], 0
-; CHECK-NEXT:    br i1 [[X1]], label [[YES1:%.*]], label [[FALLTHROUGH:%.*]]
-; CHECK:       yes1:
-; CHECK-NEXT:    store i32 0, i32* [[P:%.*]], align 4
-; CHECK-NEXT:    br label [[FALLTHROUGH]]
-; CHECK:       fallthrough:
 ; CHECK-NEXT:    [[X2:%.*]] = icmp eq i32 [[B:%.*]], 0
-; CHECK-NEXT:    br i1 [[X2]], label [[YES2:%.*]], label [[END:%.*]]
-; CHECK:       yes2:
-; CHECK-NEXT:    store i32 1, i32* [[P]], align 4
-; CHECK-NEXT:    br label [[END]]
-; CHECK:       end:
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    [[TMP0:%.*]] = or i1 [[X1]], [[X2]]
+; CHECK-NEXT:    br i1 [[TMP0]], label [[TMP1:%.*]], label [[TMP2:%.*]]
+; CHECK:         [[DOT:%.*]] = zext i1 [[X2]] to i32
+; CHECK-NEXT:    store i32 [[DOT]], i32* [[P:%.*]], align 4
+; CHECK-NEXT:    br label [[TMP2]]
+; CHECK:         ret void
 ;
 entry:
   %x1 = icmp eq i32 %a, 0