[NFC] PHINode: introduce replaceIncomingBlockWith() function, use it

Summary:
There is `PHINode::getBasicBlockIndex()`, `PHINode::setIncomingBlock()`
and `PHINode::getNumOperands()`, but no function to replace every
specified `BasicBlock*` predecessor with some other specified `BasicBlock*`.
Clearly, there are a lot of places that could use that functionality.

Reviewers: chandlerc, craig.topper, spatel, danielcdh

Reviewed By: craig.topper

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61011

llvm-svn: 359995

2 files changed, 4 insertions, 23 deletions

diff --git a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
index f89b8e498f7..92e3e9a0496 100644
--- a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -536,12 +536,6 @@ class LoopConstrainer {
     Optional<const SCEV *> HighLimit;
   };
 
-  // A utility function that does a `replaceUsesOfWith' on the incoming block
-  // set of a `PHINode' -- replaces instances of `Block' in the `PHINode's
-  // incoming block list with `ReplaceBy'.
-  static void replacePHIBlock(PHINode *PN, BasicBlock *Block,
-                              BasicBlock *ReplaceBy);
-
   // Compute a safe set of limits for the main loop to run in -- effectively the
   // intersection of `Range' and the iteration space of the original loop.
   // Return None if unable to compute the set of subranges.
@@ -643,13 +637,6 @@ public:
 
 } // end anonymous namespace
 
-void LoopConstrainer::replacePHIBlock(PHINode *PN, BasicBlock *Block,
-                                      BasicBlock *ReplaceBy) {
-  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
-    if (PN->getIncomingBlock(i) == Block)
-      PN->setIncomingBlock(i, ReplaceBy);
-}
-
 /// Given a loop with an deccreasing induction variable, is it possible to
 /// safely calculate the bounds of a new loop using the given Predicate.
 static bool isSafeDecreasingBound(const SCEV *Start,
@@ -1339,7 +1326,7 @@ LoopConstrainer::RewrittenRangeInfo LoopConstrainer::changeIterationSpaceEnd(
   // The latch exit now has a branch from `RRI.ExitSelector' instead of
   // `LS.Latch'.  The PHI nodes need to be updated to reflect that.
   for (PHINode &PN : LS.LatchExit->phis())
-    replacePHIBlock(&PN, LS.Latch, RRI.ExitSelector);
+    PN.replaceIncomingBlockWith(LS.Latch, RRI.ExitSelector);
 
   return RRI;
 }
@@ -1363,8 +1350,7 @@ BasicBlock *LoopConstrainer::createPreheader(const LoopStructure &LS,
   BranchInst::Create(LS.Header, Preheader);
 
   for (PHINode &PN : LS.Header->phis())
-    for (unsigned i = 0, e = PN.getNumIncomingValues(); i < e; ++i)
-      replacePHIBlock(&PN, OldPreheader, Preheader);
+    PN.replaceIncomingBlockWith(OldPreheader, Preheader);
 
   return Preheader;
 }
diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
index aadbc3857e4..8347dbe4598 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -1281,13 +1281,8 @@ static void moveBBContents(BasicBlock *FromBB, Instruction *InsertBefore) {
 
 static void updateIncomingBlock(BasicBlock *CurrBlock, BasicBlock *OldPred,
                                 BasicBlock *NewPred) {
-  for (PHINode &PHI : CurrBlock->phis()) {
-    unsigned Num = PHI.getNumIncomingValues();
-    for (unsigned i = 0; i < Num; ++i) {
-      if (PHI.getIncomingBlock(i) == OldPred)
-        PHI.setIncomingBlock(i, NewPred);
-    }
-  }
+  for (PHINode &PHI : CurrBlock->phis())
+    PHI.replaceIncomingBlockWith(OldPred, NewPred);
 }
 
 /// Update BI to jump to NewBB instead of OldBB. Records updates to