1) Use the new SimplifyInstructionsInBlock routine instead of the copy

in JT.

2) When cloning blocks for PHI or xor conditions, use
instsimplify to simplify the code as we go.  This allows us to 
squish common cases early in JT which opens up opportunities for
subsequent iterations, and allows it to completely simplify the
testcase.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93253 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 15 insertions, 23 deletions

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index edb0412bfe..9531311551 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1341,20 +1341,7 @@ bool JumpThreading::ThreadEdge(BasicBlock *BB,
   // At this point, the IR is fully up to date and consistent.  Do a quick scan
   // over the new instructions and zap any that are constants or dead.  This
   // frequently happens because of phi translation.
-  BI = NewBB->begin();
-  for (BasicBlock::iterator E = NewBB->end(); BI != E; ) {
-    Instruction *Inst = BI++;
-    
-    if (Value *V = SimplifyInstruction(Inst, TD)) {
-      WeakVH BIHandle(BI);
-      ReplaceAndSimplifyAllUses(Inst, V, TD);
-      if (BIHandle == 0)
-        BI = NewBB->begin();
-      continue;
-    }
-    
-    RecursivelyDeleteTriviallyDeadInstructions(Inst);
-  }
+  SimplifyInstructionsInBlock(NewBB, TD);
   
   // Threaded an edge!
   ++NumThreads;
@@ -1425,9 +1412,6 @@ bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
   // mapping and using it to remap operands in the cloned instructions.
   for (; BI != BB->end(); ++BI) {
     Instruction *New = BI->clone();
-    New->setName(BI->getName());
-    PredBB->getInstList().insert(OldPredBranch, New);
-    ValueMapping[BI] = New;
     
     // Remap operands to patch up intra-block references.
     for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
@@ -1436,6 +1420,19 @@ bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
         if (I != ValueMapping.end())
           New->setOperand(i, I->second);
       }
+
+    // If this instruction can be simplified after the operands are updated,
+    // just use the simplified value instead.  This frequently happens due to
+    // phi translation.
+    if (Value *IV = SimplifyInstruction(New, TD)) {
+      delete New;
+      ValueMapping[BI] = IV;
+    } else {
+      // Otherwise, insert the new instruction into the block.
+      New->setName(BI->getName());
+      PredBB->getInstList().insert(OldPredBranch, New);
+      ValueMapping[BI] = New;
+    }
   }
   
   // Check to see if the targets of the branch had PHI nodes. If so, we need to
diff --git a/test/Transforms/JumpThreading/basic.ll b/test/Transforms/JumpThreading/basic.ll
index 34b4243d5b..503d301892 100644
--- a/test/Transforms/JumpThreading/basic.ll
+++ b/test/Transforms/JumpThreading/basic.ll
@@ -407,12 +407,7 @@ T2:
 F2:
 	ret i32 %v1
         
-;; FIXME: CONSTANT FOLD on clone and when phi gets eliminated.
-
-; CHECK:      Entry.Merge_crit_edge:
-; CHECK-NEXT:   %M1 = icmp eq i32 192, 192
-; CHECK-NEXT:   %N2 = xor i1 true, %M1
-; CHECK-NEXT:   br i1 %N2, label %T2, label %F2
+; CHECK:   br i1 %cond, label %F2, label %Merge
 
 ; CHECK:      Merge:
 ; CHECK-NEXT:   %M = icmp eq i32 %v1, 192