- Insert new instructions before DomBlock's terminator,

   which is simpler than finding a place to insert in BB.
 - Don't perform the 'if condition hoisting' xform on certain
   i1 PHIs, as it interferes with switch formation.

This re-fixes "example 7", without breaking the world hopefully.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121764 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 7 deletions

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 1fbbb42..bbdde4b 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1168,11 +1168,11 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) {
   // that need to be moved to the dominating block.
   SmallPtrSet<Instruction*, 4> AggressiveInsts;
   
-  BasicBlock::iterator AfterPHIIt = BB->begin();
-  while (isa<PHINode>(AfterPHIIt)) {
-    PHINode *PN = cast<PHINode>(AfterPHIIt++);
+  for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) {
+    PHINode *PN = cast<PHINode>(II++);
     if (Value *V = SimplifyInstruction(PN, TD)) {
       PN->replaceAllUsesWith(V);
+      PN->eraseFromParent();
       continue;
     }
     
@@ -1186,6 +1186,14 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) {
   PN = dyn_cast<PHINode>(BB->begin());
   if (PN == 0) return true;
   
+  // Don't fold i1 branches on PHIs which contain binary operators.  These can
+  // often be turned into switches and other things.
+  if (PN->getType()->isIntegerTy(1) &&
+      (isa<BinaryOperator>(PN->getIncomingValue(0)) ||
+       isa<BinaryOperator>(PN->getIncomingValue(1)) ||
+       isa<BinaryOperator>(IfCond)))
+    return false;
+  
   // If we all PHI nodes are promotable, check to make sure that all
   // instructions in the predecessor blocks can be promoted as well.  If
   // not, we won't be able to get rid of the control flow, so it's not
@@ -1224,15 +1232,16 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) {
       
   // If we can still promote the PHI nodes after this gauntlet of tests,
   // do all of the PHI's now.
-
+  Instruction *InsertPt = DomBlock->getTerminator();
+  
   // Move all 'aggressive' instructions, which are defined in the
   // conditional parts of the if's up to the dominating block.
   if (IfBlock1)
-    DomBlock->getInstList().splice(DomBlock->getTerminator(),
+    DomBlock->getInstList().splice(InsertPt,
                                    IfBlock1->getInstList(), IfBlock1->begin(),
                                    IfBlock1->getTerminator());
   if (IfBlock2)
-    DomBlock->getInstList().splice(DomBlock->getTerminator(),
+    DomBlock->getInstList().splice(InsertPt,
                                    IfBlock2->getInstList(), IfBlock2->begin(),
                                    IfBlock2->getTerminator());
   
@@ -1241,7 +1250,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) {
     Value *TrueVal  = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
     Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
     
-    Value *NV = SelectInst::Create(IfCond, TrueVal, FalseVal, "", AfterPHIIt);
+    Value *NV = SelectInst::Create(IfCond, TrueVal, FalseVal, "", InsertPt);
     PN->replaceAllUsesWith(NV);
     NV->takeName(PN);
     PN->eraseFromParent();