[CodeGen] Introduce MachineBasicBlock::replacePhiUsesWith helper and use it. NFC

Summary:
Found a couple of places in the code where all the PHI nodes
of a MBB is updated, replacing references to one MBB by
reference to another MBB instead.

This patch simply refactors the code to use a common helper
(MachineBasicBlock::replacePhiUsesWith) for such PHI node
updates.

Reviewers: t.p.northover, arsenm, uabelho

Subscribers: wdng, hiraditya, jsji, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66750

llvm-svn: 370463

1 files changed, 1 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/MachinePipeliner.cpp b/llvm/lib/CodeGen/MachinePipeliner.cpp
index 584b2a1eaec..3814f77f5be 100644
--- a/llvm/lib/CodeGen/MachinePipeliner.cpp
+++ b/llvm/lib/CodeGen/MachinePipeliner.cpp
@@ -2234,15 +2234,7 @@ void SwingSchedulerDAG::generateEpilog(SMSchedule &Schedule, unsigned LastStage,
   }
 
   // Fix any Phi nodes in the loop exit block.
-  for (MachineInstr &MI : *LoopExitBB) {
-    if (!MI.isPHI())
-      break;
-    for (unsigned i = 2, e = MI.getNumOperands() + 1; i != e; i += 2) {
-      MachineOperand &MO = MI.getOperand(i);
-      if (MO.getMBB() == BB)
-        MO.setMBB(PredBB);
-    }
-  }
+  LoopExitBB->replacePhiUsesWith(BB, PredBB);
 
   // Create a branch to the new epilog from the kernel.
   // Remove the original branch and add a new branch to the epilog.