From 7009cd35549c753722bebe57378f566388032fba Mon Sep 17 00:00:00 2001
From: Chen Li <meloli87@gmail.com>
Date: Fri, 23 Oct 2015 21:13:01 +0000
Subject: [PATCH] Revert rL251061 [SimplifyCFG] Extend SimplifyResume to handle
 phi of trivial landing pad.

llvm-svn: 251149
---
 llvm/lib/Transforms/Utils/SimplifyCFG.cpp     | 76 +++----------------
 .../Transforms/SimplifyCFG/invoke_unwind.ll   | 42 ----------
 2 files changed, 11 insertions(+), 107 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index ce550dc7fd15..e435537c3a7d 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2905,80 +2905,26 @@ bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) {
   // exception then zap the landing pad, turning its invokes into calls.
   BasicBlock *BB = RI->getParent();
   LandingPadInst *LPInst = dyn_cast<LandingPadInst>(BB->getFirstNonPHI());
-
-  // If RI->getValue() is a landing pad, check if the first instruction is
-  // the same landing pad that caused control to branch here. If RI->getValue
-  // is a phi of landing pad, check its predecessor blocks to see if any of
-  // them contains a trivial landing pad.
-  if (RI->getValue() != LPInst && !isa<PHINode>(RI->getValue()))
+  if (RI->getValue() != LPInst)
+    // Not a landing pad, or the resume is not unwinding the exception that
+    // caused control to branch here.
     return false;
 
-  // Check that there are no other instructions except for debug intrinsics
-  // between the landing pad (or phi of landing pad) and resume instruction.
-  BasicBlock::iterator I = cast<Instruction>(RI->getValue()), E = RI;
+  // Check that there are no other instructions except for debug intrinsics.
+  BasicBlock::iterator I = LPInst->getIterator(), E = RI->getIterator();
   while (++I != E)
     if (!isa<DbgInfoIntrinsic>(I))
       return false;
 
-  SmallVector<BasicBlock *, 4> TrivialUnwindBlocks;
-  if (RI->getValue() == LPInst) {
-    // Landing pad is in current block, which has already been checked.
-    TrivialUnwindBlocks.push_back(BB);
-  } else {
-    // Check incoming blocks to see if any of them are trivial.
-    auto *PhiLPInst = cast<PHINode>(RI->getValue());
-    for (unsigned i = 0; i < PhiLPInst->getNumIncomingValues(); i++) {
-      auto *IncomingBB = PhiLPInst->getIncomingBlock(i);
-      auto *IncomingValue = PhiLPInst->getIncomingValue(i);
-
-      auto *LandingPad =
-          dyn_cast<LandingPadInst>(IncomingBB->getFirstNonPHI());
-      // Not the landing pad that caused the control to branch here.
-      if (IncomingValue != LandingPad)
-        continue;
-
-      bool isTrivial = true;
-
-      I = IncomingBB->getFirstNonPHI();
-      E = IncomingBB->getTerminator();
-      while (++I != E)
-        if (!isa<DbgInfoIntrinsic>(I)) {
-          isTrivial = false;
-          break;
-        }
-
-      if (isTrivial)
-        TrivialUnwindBlocks.push_back(IncomingBB);
-    }
-  }
-
   // Turn all invokes that unwind here into calls and delete the basic block.
-  for (auto *TrivialBB : TrivialUnwindBlocks) {
-    if (isa<PHINode>(RI->getValue())) {
-      // Blocks that will be deleted should also be removed
-      // from the phi node.
-      BB->removePredecessor(TrivialBB, true);
-    }
-
-    for (pred_iterator PI = pred_begin(TrivialBB), PE = pred_end(TrivialBB);
-         PI != PE;) {
-      BasicBlock *Pred = *PI++;
-      removeUnwindEdge(Pred);
-    }
-
-    // The landingpad is now unreachable.  Zap it.
-    if (TrivialBB == BB)
-      BB = nullptr;
-    TrivialBB->eraseFromParent();
+  for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
+    BasicBlock *Pred = *PI++;
+    removeUnwindEdge(Pred);
   }
 
-  // Delete the resume block if all its predecessors have been deleted, and we
-  // haven't already deleted it above when deleting the landing pad blocks.
-  if (BB && pred_begin(BB) == pred_end(BB)) {
-    BB->eraseFromParent();
-  }
-
-  return TrivialUnwindBlocks.size() != 0;
+  // The landingpad is now unreachable.  Zap it.
+  BB->eraseFromParent();
+  return true;
 }
 
 bool SimplifyCFGOpt::SimplifyCleanupReturn(CleanupReturnInst *RI) {
diff --git a/llvm/test/Transforms/SimplifyCFG/invoke_unwind.ll b/llvm/test/Transforms/SimplifyCFG/invoke_unwind.ll
index b1d0c404d57a..3b4c09d96f77 100644
--- a/llvm/test/Transforms/SimplifyCFG/invoke_unwind.ll
+++ b/llvm/test/Transforms/SimplifyCFG/invoke_unwind.ll
@@ -17,46 +17,4 @@ Rethrow:
         resume { i8*, i32 } %exn
 }
 
-declare i64 @dummy1()
-declare i64 @dummy2()
-
-; This testcase checks to see if simplifycfg pass can convert two invoke 
-; instructions to call instructions if they share a common trivial unwind
-; block.
-define i64 @test2(i1 %cond) personality i32 (...)* @__gxx_personality_v0 {
-entry:
-; CHECK-LABEL: @test2(
-; CHECK: %call1 = call i64 @dummy1()
-; CHECK: %call2 = call i64 @dummy2()
-; CHECK-NOT: resume { i8*, i32 } %lp
-  br i1 %cond, label %br1, label %br2
-
-br1:
-  %call1 = invoke i64 @dummy1()
-          to label %invoke.cont unwind label %lpad1
-          
-br2: 
-  %call2 = invoke i64 @dummy2()
-          to label %invoke.cont unwind label %lpad2
-          
-invoke.cont:
-  %c = phi i64 [%call1, %br1], [%call2, %br2]
-  ret i64 %c 
-  
-  
-lpad1:
-  %0 = landingpad { i8*, i32 }
-          cleanup
-  br label %rethrow 
-
-lpad2:
-  %1 = landingpad { i8*, i32 }
-          cleanup
-  br label %rethrow
-
-rethrow:
-  %lp = phi { i8*, i32 } [%0, %lpad1], [%1, %lpad2]
-  resume { i8*, i32 } %lp
-}
-
 declare i32 @__gxx_personality_v0(...)